--- name: "pylint" section: "1" platform: "linux" package: "python-pylint" version: "4.0.7-1" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/pylint" --- # pylint(1) Pylint Documentation \[image\] \\[image\] \\[image: PyPI Package version\] \[image\] \\[image: Documentation Status\] \[image\] \\[image\] \\[image\] \\[image: pre-commit.ci status\] \[image\] \\[image: CII Best Practices\] \[image\] \\[image: OpenSSF Scorecard\] \[image\] \\[image: Discord\] \[image\] \.SH WHAT IS PYLINT? Pylint is a static code analyser \ for Python 2 or 3. The latest version supports Python 3.10.0 and above. Pylint analyses your code without actually running it. It checks for errors, enforces a coding standard, looks for code smells \, and can make suggestions about how the code could be refactored. ## NAME pylint - Pylint Documentation \[image\]\ \\[image\]\ \\[image: PyPI Package version\] \[image\]\ \\[image: Documentation Status\] \[image\]\ \\[image\]\ \\[image\]\ \\[image: pre-commit.ci status\] \[image\]\ \\[image: CII Best Practices\] \[image\]\ \\[image: OpenSSF Scorecard\] \[image\]\ \\[image: Discord\] \[image\]\ \.SH WHAT IS PYLINT? Pylint is a static code analyser \ for Python 2 or 3. The latest version supports Python 3.10.0 and above. Pylint analyses your code without actually running it. It checks for errors, enforces a coding standard, looks for code smells \, and can make suggestions about how the code could be refactored. ## INSTALL For command line use, pylint is installed with: ``` pip install pylint ``` Or if you want to also check spelling with **enchant** (you might need to install the enchant C library \): ``` pip install pylint[spelling] ``` It can also be integrated in most editors or IDEs. More information can be found in the documentation \. ## WHAT DIFFERENTIATES PYLINT? Pylint is not trusting your typing and is inferring the actual values of nodes (for a start because there was no typing when pylint started off) using its internal code representation (astroid). If your code is **import logging as argparse**, Pylint can check and know that **argparse.error(...)** is in fact a logging call and not an argparse call. This makes pylint slower, but it also lets pylint find more issues if your code is not fully typed. \[inference\] is the killer feature that keeps us using \[pylint\] in our project despite how painfully slow it is. - Realist pylint user \, 2022 pylint, not afraid of being a little slower than it already is, is also a lot more thorough than other linters. There are more checks, including some opinionated ones that are deactivated by default but can be enabled using configuration. ## HOW TO USE PYLINT Pylint isn't smarter than you: it may warn you about things that you have conscientiously done or check for some things that you don't care about. During adoption, especially in a legacy project where pylint was never enforced, it's best to start with the **--errors-only** flag, then disable convention and refactor messages with **--disable=C,R** and progressively re-evaluate and re-enable messages as your priorities evolve. Pylint is highly configurable and permits to write plugins in order to add your own checks (for example, for internal libraries or an internal rule). Pylint also has an ecosystem of existing plugins for popular frameworks and third-party libraries. **Note:** Pylint supports the Python standard library out of the box. Third-party libraries are not always supported, so a plugin might be needed. A good place to start is **PyPI** which often returns a plugin by searching for **pylint \**. pylint-pydantic \, pylint-django \ and pylint-sonarjson \ are examples of such plugins. More information about plugins and how to load them can be found at plugins \. ## ADVISED LINTERS ALONGSIDE PYLINT Projects that you might want to use alongside pylint include ruff \ (**really** fast, with builtin auto-fix and a large number of checks taken from popular linters, but implemented in **rust**) or flake8 \ (a framework to implement your own checks in python using **ast** directly), mypy \, pyright \ / pylance or pyre \ (typing checks), bandit \ (security oriented checks), black \ and isort \ (auto-formatting), autoflake \ (automated removal of unused imports or variables), pyupgrade \ (automated upgrade to newer python syntax) and pydocstringformatter \ (automated pep257). ## ADDITIONAL TOOLS INCLUDED IN PYLINT Pylint ships with two additional tools: - • pyreverse \ (standalone tool that generates package and class diagrams.) - • symilar \ (duplicate code finder that is also integrated in pylint) ## CONTRIBUTING We welcome all forms of contributions such as updates for documentation, new code, checking issues for duplicates or telling us that we can close them, confirming that issues still exist, creating issues because you found a bug or want a feature \, etc. Everything is much appreciated! Please follow the code of conduct \ and check the Contributor Guides \ if you want to make a code contribution. ## SHOW YOUR USAGE You can place this badge in your README to let others know your project uses pylint. \[image\]\ \.UNINDENT Learn how to add a badge to your documentation in the badge documentation \. ## LICENSE pylint is, with a few exceptions listed below, GPLv2 \. The icon files are licensed under the CC BY-SA 4.0 \ license: - • doc/logo.png \ - • doc/logo.svg \ ## SUPPORT Please check the contact information \. | | | | --- | --- | | \[image: Tidelift\] \[image\] | Professional support for pylint is available as part of the Tidelift Subscription \. Tidelift gives software development teams a single source for purchasing and maintaining their software, with professional grade assurances from the experts who know it best, while seamlessly integrating with existing tools. | ### Tutorial This tutorial is all about approaching coding standards with little or no knowledge of in-depth programming or the code standards themselves. It's the equivalent of skipping the manual and jumping right in. The command line prompt for these examples is: ``` tutor Desktop$ ``` ### Getting Started Running Pylint with the **--help** arguments will give you an idea of the arguments available. Do that now, i.e.: ``` pylint --help ``` A couple of the options that we'll focus on here are: ``` Commands: --help-msg= --generate-toml-config Messages control: --disable= Reports: --reports= --output-format= ``` If you need more detail, you can also ask for an even longer help message: ``` pylint --long-help ``` Pay attention to the last bit of this longer help output. This gives you a hint of what Pylint is going to **pick on**: ``` Output: Using the default text output, the message format is : MESSAGE_TYPE: LINE_NUM:[OBJECT:] MESSAGE There are 5 kind of message types : * (C) convention, for programming standard violation * (R) refactor, for bad code smell * (W) warning, for python specific problems * (E) error, for probable bugs in the code * (F) fatal, if an error occurred which prevented pylint from doing further processing. ``` When Pylint is first run on a fresh piece of code, a common complaint is that it is too **noisy**. The default configuration enforce a lot of warnings. We'll use some of the options we noted above to make it suit your preferences a bit better. ### Your First Pylint'ing We'll use a basic Python script with black \ already applied on it, as fodder for our tutorial. The starting code we will use is called **simplecaesar.py** and is here in its entirety: ``` #!/usr/bin/env python3 import string shift = 3 choice = input("would you like to encode or decode?") word = input("Please enter text") letters = string.ascii_letters + string.punctuation + string.digits encoded = "" if choice == "encode": for letter in word: if letter == " ": encoded = encoded + " " else: x = letters.index(letter) + shift encoded = encoded + letters[x] if choice == "decode": for letter in word: if letter == " ": encoded = encoded + " " else: x = letters.index(letter) - shift encoded = encoded + letters[x] print(encoded) ``` Let's get started. If we run this: ``` tutor Desktop$ pylint simplecaesar.py ************* Module simplecaesar simplecaesar.py:1:0: C0114: Missing module docstring (missing-module-docstring) simplecaesar.py:5:0: C0103: Constant name "shift" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:8:0: C0103: Constant name "letters" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:9:0: C0103: Constant name "encoded" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:13:12: C0103: Constant name "encoded" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:15:12: C0103: Constant name "x" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:16:12: C0103: Constant name "encoded" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:20:12: C0103: Constant name "encoded" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:22:12: C0103: Constant name "x" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:23:12: C0103: Constant name "encoded" doesn't conform to UPPER_CASE naming style (invalid-name) ----------------------------------- Your code has been rated at 4.74/10 ``` We can see the second line is: ``` "simplecaesar.py:1:0: C0114: Missing module docstring (missing-module-docstring)" ``` This basically means that line 1 at column 0 violates the convention **C0114**. Another piece of information is the message symbol between parens, **missing-module-docstring**. If we want to read up a bit more about that, we can go back to the command line and try this: ``` tutor Desktop$ pylint --help-msg=missing-module-docstring :missing-module-docstring (C0114): *Missing module docstring* Used when a module has no docstring.Empty modules do not require a docstring. This message belongs to the basic checker. ``` That one was a bit of a no-brainer, but we can also run into error messages where we are unfamiliar with the underlying code theory. ### The Next Step Now that we got some configuration stuff out of the way, let's see what we can do with the remaining warnings. If we add a docstring to describe what the code is meant to do that will help. There are **invalid-name** messages that we will get to later. Here is the updated code: ``` #!/usr/bin/env python3 """This script prompts a user to enter a message to encode or decode using a classic Caesar shift substitution (3 letter shift)""" import string shift = 3 choice = input("would you like to encode or decode?") word = input("Please enter text") letters = string.ascii_letters + string.punctuation + string.digits encoded = "" if choice == "encode": for letter in word: if letter == " ": encoded = encoded + " " else: x = letters.index(letter) + shift encoded = encoded + letters[x] if choice == "decode": for letter in word: if letter == " ": encoded = encoded + " " else: x = letters.index(letter) - shift encoded = encoded + letters[x] print(encoded) ``` Here is what happens when we run it: ``` tutor Desktop$ pylint simplecaesar.py ************* Module simplecaesar simplecaesar.py:8:0: C0103: Constant name "shift" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:11:0: C0103: Constant name "letters" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:12:0: C0103: Constant name "encoded" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:16:12: C0103: Constant name "encoded" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:18:12: C0103: Constant name "x" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:19:12: C0103: Constant name "encoded" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:23:12: C0103: Constant name "encoded" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:25:12: C0103: Constant name "x" doesn't conform to UPPER_CASE naming style (invalid-name) simplecaesar.py:26:12: C0103: Constant name "encoded" doesn't conform to UPPER_CASE naming style (invalid-name) ------------------------------------------------------------------ Your code has been rated at 5.26/10 (previous run: 4.74/10, +0.53) ``` Nice! Pylint told us how much our code rating has improved since our last run, and we're down to just the **invalid-name** messages. There are fairly well defined conventions around naming things like instance variables, functions, classes, etc. The conventions focus on the use of UPPERCASE and lowercase as well as the characters that separate multiple words in the name. This lends itself well to checking via a regular expression, thus the **should match ((\[A-Z\_\]\[A-Z1-9\_\]\*)\|(\_\_.\*\_\_))$**. In this case Pylint is telling us that those variables appear to be constants and should be all UPPERCASE. This is an in-house convention that has lived with Pylint since its inception. You too can create your own in-house naming conventions but for the purpose of this tutorial, we want to stick to the PEP 8 \ standard. In this case, the variables we declared should follow the convention of all lowercase. The appropriate rule would be something like: "should match \[a-z\_\]\[a-z0-9\_\]{2,30}$". Notice the lowercase letters in the regular expression (a-z versus A-Z). If we run that rule using a **--const-rgx='\[a-z\\\_\]\[a-z0-9\\\_\]{2,30}$'** option, it will now be quite quiet: ``` tutor Desktop$ pylint simplecaesar.py --const-rgx='[a-z\_][a-z0-9\_]{2,30}$' ************* Module simplecaesar simplecaesar.py:18:12: C0103: Constant name "x" doesn't conform to '[a-z\\_][a-z0-9\\_]{2,30}$' pattern (invalid-name) simplecaesar.py:25:12: C0103: Constant name "x" doesn't conform to '[a-z\\_][a-z0-9\\_]{2,30}$' pattern (invalid-name) ------------------------------------------------------------------ Your code has been rated at 8.95/10 (previous run: 5.26/10, +3.68) ``` You can read up \ on regular expressions or use a website to help you \. **Tip:** It would really be a pain to specify that regex on the command line all the time, particularly if we're using many other options. That's what a configuration file is for. We can configure our Pylint to store our options for us so we don't have to declare them on the command line. Using a configuration file is a nice way of formalizing your rules and quickly sharing them with others. Invoking **pylint --generate-toml-config** will create a sample **.toml** section with all the options set and explained in comments. This can then be added to your **pyproject.toml** file or any other **.toml** file pointed to with the **--rcfile** option. ### Installation Pylint can be installed: - • As a command line tool \<#installation\> - • Integrated in your editor/ide \<#ide-integration\> - • As a pre-commit hook \<#pre-commit-integration\> - • For multiple python interpreters in your continuous integration \<#continuous-integration\> ### Command line installation Pylint is installable using a package manager. Your package manager will find a version that works with your interpreter. We recommend **pip**: ``` pip install pylint ``` Or if you want to also check spelling with **enchant** (you might need to install the enchant C library \): ``` pip install pylint[spelling] ``` The newest pylint supports all Python interpreters that are not past end of life. We recommend to use the latest interpreter because we rely on the **ast** builtin module that gets better with each new Python interpreter. For example a Python 3.6 interpreter can't analyse 3.8 syntax (amongst others, because of the new walrus operator) while a 3.8 interpreter can also deal with Python 3.6. See using pylint with multiple interpreters \<#continuous-integration\> for more details. **Note:** You can also use **conda** or your system package manager on debian based OS. These package managers lag a little behind as they are maintained by a separate entity on a slower release cycle. ``` conda install pylint ``` ``` sudo apt-get install pylint ``` ### Editor and IDE integration Pylint can be integrated in various editors and IDE's. Below you can find tutorials for some of the most common ones. - • Eclipse \ - • Emacs \ - • Eric IDE \ in the *Project \> Check* menu, - • gedit \ (another option for gedit \) - • Flymake \<#pylint-in-flymake\> - • Jupyter Notebook \ - • Komodo \ - • Pycharm \ - • PyDev \ - • pyscripter \ in the *Tool -\> Tools* menu. - • Spyder \ in the *View -\> Panes -\> Static code analysis* - • Sublime Text \ - • TextMate \<#pylint-in-textmate\> - • Vim \ - • Visual Studio Code \ in the *Preferences -\> Settings* menu - • Visual Studio Code Pylint Extension \ - • Visual Studio \ in the *Python \> Run PyLint* command on a project's context menu. - • WingIDE \ ### Using Pylint through Flymake in Emacs **Warning:** epylint was deprecated in 2.16.0 and targeted for deletion in 3.0.0. All emacs and flymake related files were removed and their support will now happen in an external repository: \. ### Integrate Pylint with TextMate Install Pylint in the usual way: ``` pip install pylint ``` Install the Python bundle for TextMate \: - 1\. select *TextMate* \> *Preferences* - 2\. select the *Bundles* tab - 3\. find and tick the *Python* bundle in the list You should now see it in *Bundles* \> *Python*. In *Preferences*, select the *Variables* tab. If a **TM\_PYCHECKER** variable is not already listed, add it, with the value **pylint**. The default keyboard shortcut to run the syntax checker is *Control-Shift-V* - open a **.py** file in Textmate, and try it. You should see the output in a new window: PyCheckMate 1.2 – Pylint 1.4.4 No config file found, using default configuration Then all is well, and most likely Pylint will have expressed some opinions about your Python code (or will exit with **0** if your code already conforms to its expectations). If you receive a message: Please install PyChecker, PyFlakes, Pylint, PEP 8 or flake8 for more extensive code checking. That means that Pylint wasn't found, which is likely an issue with command paths - TextMate needs be looking for Pylint on the right paths. Check where Pylint has been installed, using **which**: ``` $ which pylint /usr/local/bin/pylint ``` The output will tell you where Pylint can be found; in this case, in **/usr/local/bin**. - 1\. select *TextMate* \> *Preferences* - 2\. select the *Variables* tab - 3\. find and check that a **PATH** variable exists, and that it contains the appropriate path (if the path to Pylint were **/usr/local/bin/pylint** as above, then the variable would need to contain **/usr/local/bin**). An actual example in this case might be **$PATH:/opt/local/bin:/usr/local/bin:/usr/texbin**, which includes other paths. ... and try running Pylint again. ### Pre-commit integration **pylint** can be used as a pre-commit \ hook. We however discourage it as pylint -- due to its speed -- is more suited to a continuous integration job or a git **pre-push** hook, especially if your repository is large. Since **pylint** needs to import modules and dependencies to work correctly, the hook only works with a local installation of **pylint** (in your environment). It means it can't be used with **pre-commit.ci**, and you will need to add the following to your **.pre-commit-config.yaml** ``` .. sourcecode:: yaml ``` - **ci:** skip: \[pylint\] Another limitation is that pylint should analyse all your code at once in order to best infer the actual values that result from calls. If only some of the files are given, pylint might miss a particular value's type and produce inferior inference for the subset. Since pre-commit slices the files given to it in order to parallelize the processing, the result can be degraded. It can also be unexpectedly different when the file set changes because the new slicing can change the inference. Thus the **require\_serial** option should be set to **true** if correctness and determinism are more important than parallelization to you. If you installed **pylint** locally it can be added to **.pre-commit-config.yaml** as follows: ``` - repo: local hooks: - id: pylint name: pylint entry: pylint language: system types: [python] require_serial: true args: [ "-rn", # Only display messages "-sn", # Don't display the score ] ``` You can use **args** to pass command line arguments as described in the Tutorial \<#tutorial\>. A hook with more arguments could look something like this: ``` - repo: local hooks: - id: pylint name: pylint entry: pylint language: system types: [python] args: [ "-rn", # Only display messages "-sn", # Don't display the score "--rcfile=pylintrc", # Link to your config file "--load-plugins=pylint.extensions.docparams", # Load an extension ] ``` ### Installation with multiple interpreters It's possible to analyse code written for older or multiple interpreters by using the **py-version** option and setting it to the oldest supported interpreter of your code. For example you can check that there are no **f-strings** in Python 3.5 code using Python 3.8 with an up-to-date pylint even if Python 3.5 is past end of life (EOL) and the version of pylint you use is not compatible with it. We do not guarantee that **py-version** will work for all EOL Python interpreters indefinitely, (for anything before Python 3.5, it probably won't). If a newer version does not work for you, the best available pylint might be an old version that works with your old interpreter but without the bug fixes and features of later versions. ### Show your usage You can place this badge in your README to let others know your project uses pylint. \[image\]\ \.UNINDENT Use the badge in your project's README.md (or any other Markdown file): ``` [![linting: pylint](https://img.shields.io/badge/linting-pylint-yellowgreen)](https://github.com/pylint-dev/pylint) ``` Use the badge in your project's README.rst (or any other rst file): ``` .. image:: https://img.shields.io/badge/linting-pylint-yellowgreen :target: https://github.com/pylint-dev/pylint ``` If you use GitHub Actions, and one of your CI workflows begins with "name: pylint", you can use GitHub's workflow status badges \ to show an up-to-date indication of whether pushes to your default branch pass pylint. For more detailed information, check the documentation. ### Upgrading pylint You should probably set the version of pylint in your development environment in order to choose when you actually upgrade pylint's warnings. pylint is following semver versioning. But we can't guarantee that the output between version will stays the same. What this means is that: - • In **patch release** (**1.2.3**), we only fix false positives and crashes. You can expect less messages if you set the minor and upgrade to a new patch version. But still, if you enable **useless-suppression** it still means you can get a new **useless-suppression** when a false positive that you disabled is now fixed. Also, if a library you're using was upgraded and is understood better or worse than the previous one, you could get new messages too. - • In **minor releases** (**1.2.0**), we add checks, remove checks, drop python interpreters past end of life, upgrade astroid minor/major versions and fix false negatives. You can expect a lot more change in output, the main one being new checks. - • In **major releases** (**1.0.0**) we change everything else (pylint options, json output, dev API...) while still trying to minimize disruption. You could have to change the command you're launching or the plugin and editor integration you're using. ### Usage ### Running Pylint ### On module packages or directories Pylint is meant to be called from the command line. The usage is ``` pylint [options] modules_or_packages ``` By default the **pylint** command only accepts a list of python modules and packages. On versions below 2.15, specifying a directory that is not an explicit package (with **\_\_init\_\_.py**) results in an error: ``` pylint mydir ************* Module mydir mydir/__init__.py:1:0: F0010: error while code parsing: Unable to load file mydir/__init__.py: [Errno 2] No such file or directory: 'mydir/__init__.py' (parse-error) ``` Thus, on versions before 2.15 using the **--recursive=y** option allows for linting a namespace package: ``` pylint --recursive=y mydir mymodule mypackage ``` This option makes **pylint** attempt to discover all modules (files ending with **.py** extension) and all explicit packages (all directories containing a **\_\_init\_\_.py** file). Pylint **will not import** this package or module, but it does use Python internals to locate them and as such is subject to the same rules and configuration. You should pay attention to your **PYTHONPATH**, since it is a common error to analyze an installed version of a module instead of the development version. ### On files It is also possible to analyze Python files, with a few restrictions. As a convenience, you can give it a file name if it's possible to guess a module name from the file's path using the python path. Some examples: **pylint mymodule.py** should always work since the current working directory is automatically added on top of the python path **pylint directory/mymodule.py** will work if: **directory** is a python package (i.e. has an **\_\_init\_\_.py** file), an implicit namespace package or if **directory** is in the python path. ### With implicit namespace packages If the analyzed sources use implicit namespace packages (PEP 420), the source root(s) should be specified using the **--source-roots** option. Otherwise, the package names are detected incorrectly, since implicit namespace packages don't contain an **\_\_init\_\_.py**. ### Globbing support It is also possible to specify both directories and files using globbing patterns: ``` pylint [options] packages/*/src ``` ### Command line options First of all, we have two basic (but useful) options. - **--version** show program's version number and exit - **-h, --help** show help about the command line options Pylint is architected around several checkers. You can disable a specific checker or some of its messages or message categories by specifying **--disable=\**. If you want to enable only some checkers or some message symbols, first use **--disable=all** then **--enable=\** with **\** being a comma-separated list of checker names and message symbols. See the list of available features for a description of provided checkers with their functionalities. The **--disable** and **--enable** options can be used with comma-separated lists mixing checkers, message ids and categories like **-d C,W,no-error,design** It is possible to disable all messages with **--disable=all**. This is useful to enable only a few checkers or a few messages by first disabling everything, and then re-enabling only what you need. Each checker has some specific options, which can take either a yes/no value, an integer, a python regular expression, or a comma-separated list of values (which are generally used to override a regular expression in special cases). For a full list of options, use **--help** Specifying all the options suitable for your setup and coding standards can be tedious, so it is possible to use a configuration file to specify the default values. You can specify a configuration file on the command line using the **--rcfile** option. Otherwise, Pylint searches for a configuration file in the following order and uses the first one it finds: - 1\. **pylintrc** in the current working directory - 2\. **pylintrc.toml** in the current working directory, providing it has at least one **tool.pylint.** section. - 3\. **.pylintrc** in the current working directory - 4\. **.pylintrc.toml** in the current working directory, providing it has at least one **tool.pylint.** section. - 5\. **pyproject.toml** in the current working directory, providing it has at least one **tool.pylint.** section. The **pyproject.toml** must prepend section names with **tool.pylint.**, for example **\[tool.pylint.'MESSAGES CONTROL'\]**. They can also be passed in on the command line. - 6\. **setup.cfg** in the current working directory, providing it has at least one **pylint.** section - 7\. **tox.ini** in the current working directory, providing it has at least one **pylint.** section - 8\. Pylint will search for the **pyproject.toml** file up the directories hierarchy unless it's found, or a **.git**/**.hg** directory is found, or the file system root is approached. - 9\. If the current working directory is in a Python package, Pylint searches up the hierarchy of Python packages until it finds a **pylintrc** file. This allows you to specify coding standards on a module-by-module basis. Of course, a directory is judged to be a Python package if it contains an **\_\_init\_\_.py** file. - 10\. The file named by environment variable **PYLINTRC** - 11\. if you have a home directory which isn't **/root**: - 1\. **.pylintrc** in your home directory - 2\. **.config/pylintrc** in your home directory - 12\. **/etc/pylintrc** The **--generate-toml-config** option will generate a commented configuration file on standard output according to the current configuration and exit. This includes: - • Any configuration file found as explained above - • Options appearing before **--generate-toml-config** on the Pylint command line Of course you can also start with the default values and hand-tune the configuration. Other useful global options include: - **--ignore=***\* Files or directories to be skipped. They should be base names, not paths. - **--output-format=***\* Select output format (text, json, custom). - **--msg-template=***\* Modify text output message template. - **--list-msgs** Generate pylint's messages. - **--list-msgs-enabled** Display a list of what messages are enabled and disabled with the given configuration. - **--full-documentation** Generate pylint's full documentation, in reST format. ### Parallel execution It is possible to speed up the execution of Pylint. If the running computer has more CPUs than one, then the work for checking all files could be spread across all cores via Pylints's sub-processes. This functionality is exposed via the **-j** command-line parameter. If the provided number is 0, then the total number of CPUs will be autodetected and used. Example: ``` pylint -j 4 mymodule1.py mymodule2.py mymodule3.py mymodule4.py ``` This will spawn 4 parallel Pylint sub-process, where each provided module will be checked in parallel. Discovered problems by checkers are not displayed immediately. They are shown just after checking a module is complete. You can also do your own parallelization by launching pylint multiple times on subsets of your files (like **pre-commit** with the default **require\_serial=false** does). Be aware, though: pylint should analyse all your code at once in order to best infer the actual values that result from calls. If only some of the files are given, pylint might miss a particular value's type and produce inferior inference for the subset. It can also be unexpectedly different when the file set changes because the new slicing can change the inference. So, don't do this if correctness and determinism are important to you. ### Exit codes Pylint returns bit-encoded exit codes. | | | | --- | --- | | exit code | meaning | | 0 | no error | | 1 | fatal message issued | | 2 | error message issued | | 4 | warning message issued | | 8 | refactor message issued | | 16 | convention message issued | | 32 | usage error | For example, an exit code of **20** means there was at least one warning message (4) and at least one convention message (16) and nothing else. ### Pylint output ### Output options Output by default is written to stdout. The simplest way to output to a file is with the **--output=\** option. The default format for the output is raw text. You can change this by passing pylint the **--output-format=\** option. Possible values are: - • **text** - • **parseable** - • **colorized** - • **json2**: improved json format - • **json**: old json format - • **msvs**: visual studio - • **github**: GitHub action messages \ Multiple output formats can be used at the same time by passing a comma-separated list of formats to **--output-format**. This output can be redirected to a file by giving a filename after a colon. For example, to save a json report to **somefile.json** and print a colorized report to stdout at the same time: ``` --output-format=json:somefile.json,colorized ``` ### Custom message formats You can customize the exact way information are displayed using the *--msg-template=\* option. The *format string* uses the Python new format syntax \ and the following fields are available : - **path** relative path to the file - **abspath** absolute path to the file - **line** line number - **column** column number - **end\_line** line number of the end of the node - **end\_column** column number of the end of the node - **module** module name - **obj** object within the module (if any) - **msg** text of the message - **msg\_id** the message code (eg. I0011) - **symbol** symbolic name of the message (eg. locally-disabled) - **C** one letter indication of the message category - **category** fullname of the message category For example, the former (pre 1.0) default format can be obtained with: ``` pylint --msg-template='{msg_id}:{line:3d},{column}: {obj}: {msg}' ``` A few other examples: - • the default format: ``` {path}:{line}:{column}: {msg_id}: {msg} ({symbol}) ``` - • Visual Studio compatible format (former 'msvs' output format): ``` {path}({line}): [{msg_id}{obj}] {msg} ``` - • Parseable (Emacs and all, former 'parseable' output format) format: ``` {path}:{line}: [{msg_id}({symbol}), {obj}] {msg} ``` The **--msg-template** option can only be combined with text-based reporters (**--output-format** either unspecified or one of: parseable, colorized or msvs). If both **--output-format** and **--msg-template** are specified, the **--msg-template** option will take precedence over the default line format defined by the reporter class. If **end\_line** or **end\_column** are **None**, they will be represented as an empty string by the default **TextReporter**. ### Source code analysis section For each python module, Pylint will first display a few '\*' characters followed by the name of the module. Then, a number of messages with the following format: ``` MESSAGE_TYPE: LINE_NUM:[OBJECT:] MESSAGE ``` You can get another output format, useful since it's recognized by most editors or other development tools using the **--output-format=parseable** option. The message type can be: - • \[I\]nformational messages that Pylint emits (do not contribute to your analysis score) - • \[R\]efactor for a "good practice" metric violation - • \[C\]onvention for coding standard violation - • \[W\]arning for stylistic problems, or minor programming issues - • \[E\]rror for important programming issues (i.e. most probably bug) - • \[F\]atal for errors which prevented further processing Sometimes the line of code which caused the error is displayed with a caret pointing to the error. This may be generalized in future versions of Pylint. Example (extracted from a run of Pylint on itself...): ``` ************* Module pylint.checkers.format W: 50: Too long line (86/80) W:108: Operator not followed by a space print >>sys.stderr, 'Unable to match %r', line ^ W:141: Too long line (81/80) W: 74:searchall: Unreachable code W:171:FormatChecker.process_tokens: Redefining built-in (type) W:150:FormatChecker.process_tokens: Too many local variables (20/15) W:150:FormatChecker.process_tokens: Too many branches (13/12) ``` ### Reports section Following the analysis message, Pylint can display a set of reports, each one focusing on a particular aspect of the project, such as number of messages by categories, modules dependencies. These features can be enabled through the **--reports=y** option, or its shorthand version **-ry**. For instance, the metrics report displays summaries gathered from the current run. - • the number of processed modules - • for each module, the percentage of errors and warnings - • the total number of errors and warnings - • percentage of classes, functions and modules with docstrings, and a comparison from the previous run - • percentage of classes, functions and modules with correct name (according to the coding standard), and a comparison from the previous run - • a list of external dependencies found in the code, and where they appear ### Score section Finally, Pylint displays a global evaluation score for the code, rated out of a maximum score of 10.0. This output can be suppressed through the **--score=n** option, or its shorthand version **-sn**. The evaluation formula can be overridden with the **--evaluation=\** option. ### Messages ### Messages overview Pylint can emit the following messages: ### Fatal All messages in the fatal category: ### astroid-error / F0002 **Message emitted:** **%s: %s** **Description:** *Used when an unexpected error occurred while building the Astroid representation. This is usually accompanied by a traceback. Please report such errors !* **Additional details:** This is a message linked to an internal problem in pylint. There's nothing to change in your code, but maybe in pylint's configuration or installation. Created by the main \ checker. ### config-parse-error / F0011 **Message emitted:** **error while parsing the configuration: %s** **Description:** *Used when an exception occurred while parsing a pylint configuration file.* **Additional details:** This is a message linked to a problem in your configuration not your code. Created by the main \ checker. ### fatal / F0001 **Message emitted:** **%s** **Description:** *Used when an error occurred preventing the analysis of a module (unable to find it for instance).* **Additional details:** This is a message linked to an internal problem in pylint. There's nothing to change in your code. Created by the main \ checker. ### method-check-failed / F0202 **Message emitted:** **Unable to check methods signature (%s / %s)** **Description:** *Used when Pylint has been unable to check methods signature compatibility for an unexpected reason. Please report this kind if you don't make sense of it.* **Additional details:** This is a message linked to an internal problem in pylint. There's nothing to change in your code. Created by the classes \ checker. ### parse-error / F0010 **Message emitted:** **error while code parsing: %s** **Description:** *Used when an exception occurred while building the Astroid representation which could be handled by astroid.* **Additional details:** This is a message linked to an internal problem in pylint. There's nothing to change in your code. Created by the main \ checker. All renamed messages in the fatal category: ### old-import-error / F0401 'old-import-error' has been renamed. The new message can be found at: ### import-error / E0401 **Message emitted:** **Unable to import %s** **Description:** *Used when pylint has been unable to import a module.* **Problematic code:** ``` from patlib import Path # [import-error] ``` **Correct code:** ``` from pathlib import Path ``` **Additional details:** This can happen if you're importing a package that is not installed in your environment, or if you made a typo. The solution is to install the package via pip/setup.py/wheel or fix the typo. Created by the imports \ checker. ### Error All messages in the error category: ### abstract-class-instantiated / E0110 **Message emitted:** **Abstract class %r with abstract methods instantiated** **Description:** *Used when an abstract class with \`abc.ABCMeta\` as metaclass has abstract methods and is instantiated.* **Problematic code:** ``` import abc class Animal(abc.ABC): @abc.abstractmethod def make_sound(self): pass sheep = Animal() # [abstract-class-instantiated] ``` **Correct code:** ``` import abc class Animal(abc.ABC): @abc.abstractmethod def make_sound(self): pass class Sheep(Animal): def make_sound(self): print("bhaaaaa") sheep = Sheep() ``` Created by the basic \ checker. ### access-member-before-definition / E0203 **Message emitted:** **Access to member %r before its definition line %s** **Description:** *Used when an instance member is accessed before it's actually assigned.* **Problematic code:** ``` class Unicorn: def __init__(self, fluffiness_level): if self.fluffiness_level > 9000: # [access-member-before-definition] print("It's OVER-FLUFFYYYY ! *crush glasses*") self.fluffiness_level = fluffiness_level ``` **Correct code:** ``` class Unicorn: def __init__(self, fluffiness_level): self.fluffiness_level = fluffiness_level if self.fluffiness_level > 9000: print("It's OVER-FLUFFYYYY ! *crush glasses*") ``` Created by the classes \ checker. ### assigning-non-slot / E0237 **Message emitted:** **Assigning to attribute %r not defined in class slots** **Description:** *Used when assigning to an attribute not defined in the class slots.* **Problematic code:** ``` class Student: __slots__ = ("name",) def __init__(self, name, surname): self.name = name self.surname = surname # [assigning-non-slot] self.setup() def setup(self): pass ``` **Correct code:** ``` class Student: __slots__ = ("name", "surname") def __init__(self, name, surname): self.name = name self.surname = surname self.setup() def setup(self): pass ``` Created by the classes \ checker. ### assignment-from-no-return / E1111 **Message emitted:** **Assigning result of a function call, where the function has no return** **Description:** *Used when an assignment is done on a function call but the inferred function doesn't return anything.* **Problematic code:** ``` def add(x, y): print(x + y) value = add(10, 10) # [assignment-from-no-return] ``` **Correct code:** ``` def add(x, y): return x + y value = add(10, 10) ``` Created by the typecheck \ checker. ### assignment-from-none / E1128 **Message emitted:** **Assigning result of a function call, where the function returns None** **Description:** *Used when an assignment is done on a function call but the inferred function returns nothing but None.* **Problematic code:** ``` def function(): return None f = function() # [assignment-from-none] ``` **Correct code:** ``` def function(): return None f = function() if function() else 1 ``` Created by the typecheck \ checker. ### async-context-manager-with-regular-with / E1145 **Message emitted:** **Context manager '%s' is async and should be used with 'async with'.** **Description:** *Used when an async context manager is used with a regular 'with' statement instead of 'async with'.* **Problematic code:** ``` from contextlib import asynccontextmanager @asynccontextmanager async def async_context(): yield with async_context(): # [async-context-manager-with-regular-with] print("This will cause an error at runtime") ``` **Correct code:** ``` import asyncio from contextlib import asynccontextmanager @asynccontextmanager async def async_context(): yield async def main(): async with async_context(): print("This works correctly") ``` **Related links:** - • PEP 492 - Coroutines with async and await syntax \ - • contextlib.asynccontextmanager \ Created by the typecheck \ checker. ### await-outside-async / E1142 **Message emitted:** **'await' should be used within an async function** **Description:** *Emitted when await is used outside an async function.* **Problematic code:** ``` import asyncio def main(): await asyncio.sleep(1) # [await-outside-async] ``` **Correct code:** ``` import asyncio async def main(): await asyncio.sleep(1) ``` **Related links:** - • PEP 492 \ Created by the typecheck \ checker. ### bad-configuration-section / E0014 **Message emitted:** **Out-of-place setting encountered in top level configuration-section '%s' : '%s'** **Description:** *Used when we detect a setting in the top level of a toml configuration that shouldn't be there.* **Additional details:** This error was raised when we encountered an unexpected value type in a toml configuration between pylint 2.12 and pylint 2.14 (before the argparse refactor). Created by the main \ checker. ### bad-except-order / E0701 **Message emitted:** **Bad except clauses order (%s)** **Description:** *Used when except clauses are not in the correct order (from the more specific to the more generic). If you don't fix the order, some exceptions may not be caught by the most specific handler.* **Problematic code:** ``` try: print(int(input())) except Exception: raise except TypeError: # [bad-except-order] # This block cannot be reached since TypeError exception # is caught by previous exception handler. raise ``` **Correct code:** ``` try: print(int(input())) except TypeError: raise except Exception: raise ``` Created by the exceptions \ checker. ### bad-exception-cause / E0705 **Message emitted:** **Exception cause set to something which is not an exception, nor None** **Description:** *Used when using the syntax "raise ... from ...", where the exception cause is not an exception, nor None.* **Problematic code:** ``` def divide(x, y): result = 0 try: result = x / y except ZeroDivisionError: # +1: [bad-exception-cause] raise ValueError(f"Division by zero when dividing {x} by {y} !") from result return result ``` **Correct code:** ``` def divide(x, y): result = 0 try: result = x / y except ZeroDivisionError as exc: raise ValueError(f"Division by zero when dividing {x} by {y} !") from exc return result ``` **Related links:** - • The raise statement \ - • Explicit Exception Chaining \ per PEP 3134 Created by the exceptions \ checker. ### bad-format-character / E1300 **Message emitted:** **Unsupported format character %r (%#02x) at index %d** **Description:** *Used when an unsupported format character is used in a format string.* **Problematic code:** ``` print("%s %z" % ("hello", "world")) # [bad-format-character] ``` **Correct code:** ``` print("%s %s" % ("hello", "world")) ``` **Additional details:** This check is currently only active for "old-style" string formatting as seen in the examples. See Issue #6085 \ for more information. **Related links:** - • Format String Syntax \ - • PyFormat \ Created by the string \ checker. ### bad-plugin-value / E0013 **Message emitted:** **Plugin '%s' is impossible to load, is it installed ? ('%s')** **Description:** *Used when a bad value is used in 'load-plugins'.* **Additional details:** One of your pylint plugins cannot be loaded. There's nothing to change in your code, but your pylint configuration or installation has an issue. For example, there might be a typo. The following config: ``` [MAIN] load-plugins = pylint.extensions.bad_biultin ``` Should be: ``` [MAIN] load-plugins = pylint.extensions.bad_builtin ``` Or the plugin you added is not importable in your environment. Created by the main \ checker. ### bad-reversed-sequence / E0111 **Message emitted:** **The first reversed() argument is not a sequence** **Description:** *Used when the first argument to reversed() builtin isn't a sequence (does not implement \_\_reversed\_\_, nor \_\_getitem\_\_ and \_\_len\_\_* **Problematic code:** ``` reversed({1, 2, 3, 4}) # [bad-reversed-sequence] ``` **Correct code:** ``` reversed([1, 2, 3, 4]) ``` Created by the basic \ checker. ### bad-str-strip-call / E1310 **Message emitted:** **Suspicious argument in %s.%s call** **Description:** *The argument to a str.{l,r,}strip call contains a duplicate character,* **Problematic code:** **hello\_world.py**: ``` "Hello World".strip("Hello") # [bad-str-strip-call] # >>> ' World' ``` **remove\_abc\_from\_both\_side.py**: ``` "abcbc def bacabc".strip("abcbc ") # [bad-str-strip-call] # >>> 'def' ``` **Correct code:** **hello\_world.py**: ``` "Hello World".strip("Helo") # >>> ' World' ``` **remove\_abc\_from\_both\_side.py**: ``` "abcbc def bacabc".strip("abc ") # >>> 'def' ``` **Additional details:** A common misconception is that **str.strip('Hello')** removes the *substring* **'Hello'** from the beginning and end of the string. This is **not** the case. From the documentation \: \> The chars argument is not a prefix or suffix; rather, all combinations of its values are stripped Duplicated characters in the **str.strip** call, besides not having any effect on the actual result, may indicate this misunderstanding. **Related links:** - • Documentation: str.strip(\[chars\]) \ Created by the string \ checker. ### bad-string-format-type / E1307 **Message emitted:** **Argument %r does not match format type %r** **Description:** *Used when a type required by format string is not suitable for actual argument type* **Problematic code:** ``` print("%d" % "1") # [bad-string-format-type] ``` **Correct code:** ``` print("%d" % 1) ``` **Additional details:** This check is currently only active for "old-style" string formatting as seen in the examples. See Issue #6085 \ for more information. **Related links:** - • Format String Syntax \ - • PyFormat \ Created by the string \ checker. ### bad-super-call / E1003 **Message emitted:** **Bad first argument %r given to super()** **Description:** *Used when another argument than the current class is given as first argument of the super builtin.* **Problematic code:** ``` class Animal: pass class Tree: pass class Cat(Animal): def __init__(self): super(Tree, self).__init__() # [bad-super-call] super(Animal, self).__init__() ``` **Correct code:** ``` class Animal: pass class Tree: pass class Cat(Animal): def __init__(self): super(Animal, self).__init__() ``` **Additional details:** In Python 2.7, **super()** has to be called with its own class and **self** as arguments (**super(Cat, self)**), which can lead to a mix up of parent and child class in the code. In Python 3 the recommended way is to call **super()** without arguments (see also **super-with-arguments**). One exception is calling **super()** on a non-direct parent class. This can be used to get a method other than the default method returned by the **mro()**. **Related links:** - • Documentation for super() \ Created by the newstyle \ checker. ### bare-name-capture-pattern / E1901 **Message emitted:** **The name capture \`case %s\` makes the remaining patterns unreachable. Use a dotted name (for example an enum) to fix this.** **Description:** *Emitted when a name capture pattern is used in a match statement and there are case statements below it.* **Problematic code:** ``` red = 0 green = 1 blue = 2 def func(color): match color: case red: # [bare-name-capture-pattern] print("I see red!") case green: # [bare-name-capture-pattern] print("Grass is green") case blue: print("I'm feeling the blues :(") ``` **Correct code:** ``` from enum import Enum class Color(Enum): RED = 0 GREEN = 1 BLUE = 2 def func(color: Color) -> None: match color: case Color.RED: print("I see red!") case Color.GREEN: print("Grass is green") case Color.BLUE: print("I'm feeling the blues :(") ``` **Related links:** - • PEP 636 \ Created by the match\_statements \ checker. ### bidirectional-unicode / E2502 **Message emitted:** **Contains control characters that can permit obfuscated code executed differently than displayed** **Description:** *bidirectional unicode are typically not displayed characters required to display right-to-left (RTL) script (i.e. Chinese, Japanese, Arabic, Hebrew, ...) correctly. So can you trust this code? Are you sure it displayed correctly in all editors? If you did not write it or your language is not RTL, remove the special characters, as they could be used to trick you into executing code, that does something else than what it looks like.* *More Information:* *https://en.wikipedia.org/wiki/Bidirectional\_text* *https://trojansource.codes/* **Problematic code:** ``` # +1: [bidirectional-unicode] example = "x‏" * 100 # "‏x" is assigned ``` **Correct code:** ``` example = "x[U+2194]" * 100 ``` Created by the unicode\_checker \ checker. ### broken-collections-callable / E6005 **Message emitted:** **'collections.abc.Callable' inside Optional and Union is broken in 3.9.0 / 3.9.1 (use 'typing.Callable' instead)** **Description:** *\`\`collections.abc.Callable\`\` inside Optional and Union is broken in Python 3.9.0 and 3.9.1. Use \`\`typing.Callable\`\` for these cases instead. https://bugs.python.org/issue42965* **Problematic code:** ``` from collections.abc import Callable from typing import Optional def func() -> Optional[Callable[[int], None]]: # [broken-collections-callable] ... ``` **Correct code:** ``` from typing import Callable, Optional def func() -> Optional[Callable[[int], None]]: ... ``` **Configuration file:** ``` [main] py-version=3.9 load-plugins=pylint.extensions.typing ``` **Related links:** - • bpo-42965 \ **Note:** This message is emitted by the optional 'typing' \<#pylint-extensions-typing\> checker, which requires the **pylint.extensions.typing** plugin to be loaded. Created by the typing \ checker. ### broken-noreturn / E6004 **Message emitted:** **'NoReturn' inside compound types is broken in 3.7.0 / 3.7.1** **Description:** *\`\`typing.NoReturn\`\` inside compound types is broken in Python 3.7.0 and 3.7.1. If not dependent on runtime introspection, use string annotation instead. E.g. \`\`Callable\[..., 'NoReturn'\]\`\`. https://bugs.python.org/issue34921* **Problematic code:** ``` from typing import NoReturn, Union def exploding_apple(apple) -> Union[None, NoReturn]: # [broken-noreturn] print(f"{apple} is about to explode") ``` **Correct code:** ``` from typing import NoReturn def exploding_apple(apple) -> NoReturn: print(f"{apple} is about to explode") raise Exception("{apple} exploded !") ``` **Configuration file:** ``` [main] py-version=3.7 load-plugins=pylint.extensions.typing ``` **Note:** This message is emitted by the optional 'typing' \<#pylint-extensions-typing\> checker, which requires the **pylint.extensions.typing** plugin to be loaded. Created by the typing \ checker. ### catching-non-exception / E0712 **Message emitted:** **Catching an exception which doesn't inherit from Exception: %s** **Description:** *Used when a class which doesn't inherit from Exception is used as an exception in an except clause.* **Problematic code:** ``` class FooError: pass try: 1 / 0 except FooError: # [catching-non-exception] pass ``` **Correct code:** ``` class FooError(Exception): pass try: 1 / 0 except FooError: pass ``` Created by the exceptions \ checker. ### class-variable-slots-conflict / E0242 **Message emitted:** **Value %r in slots conflicts with class variable** **Description:** *Used when a value in \_\_slots\_\_ conflicts with a class variable, property or method.* **Problematic code:** ``` class Person: # +1: [class-variable-slots-conflict, class-variable-slots-conflict, class-variable-slots-conflict] __slots__ = ("age", "name", "say_hi") name = None def __init__(self, age, name): self.age = age self.name = name @property def age(self): return self.age def say_hi(self): print(f"Hi, I'm {self.name}.") ``` **Correct code:** ``` class Person: __slots__ = ("_age", "name") def __init__(self, age, name): self._age = age self.name = name @property def age(self): return self._age def say_hi(self): print(f"Hi, I'm {self.name}.") ``` Created by the classes \ checker. ### declare-non-slot / E0245 **Message emitted:** **No such name %r in \_\_slots\_\_** **Description:** *Raised when a type annotation on a class is absent from the list of names in \_\_slots\_\_, and \_\_slots\_\_ does not contain a \_\_dict\_\_ entry.* **Problematic code:** ``` class Student: __slots__ = ("name",) name: str surname: str # [declare-non-slot] ``` **Correct code:** ``` class Student: __slots__ = ("name", "surname") name: str surname: str ``` Created by the classes \ checker. ### dict-iter-missing-items / E1141 **Message emitted:** **Unpacking a dictionary in iteration without calling .items()** **Description:** *Emitted when trying to iterate through a dict without calling .items()* **Problematic code:** ``` data = {"Paris": 2_165_423, "New York City": 8_804_190, "Tokyo": 13_988_129} for city, population in data: # [dict-iter-missing-items] print(f"{city} has population {population}.") ``` **Correct code:** ``` data = {"Paris": 2_165_423, "New York City": 8_804_190, "Tokyo": 13_988_129} for city, population in data.items(): print(f"{city} has population {population}.") ``` Created by the typecheck \ checker. ### duplicate-argument-name / E0108 **Message emitted:** **Duplicate argument name %r in function definition** **Description:** *Duplicate argument names in function definitions are syntax errors.* **Problematic code:** ``` def get_fruits(apple, banana, apple): # [duplicate-argument-name] pass ``` **Correct code:** ``` def get_fruits(apple, banana, orange): pass ``` Created by the basic \ checker. ### duplicate-bases / E0241 **Message emitted:** **Duplicate bases for class %r** **Description:** *Duplicate use of base classes in derived classes raise TypeErrors.* **Problematic code:** ``` class Animal: pass class Cat(Animal, Animal): # [duplicate-bases] pass ``` **Correct code:** ``` class Animal: pass class Bird(Animal): pass class Cat(Animal): pass ``` Created by the classes \ checker. ### format-needs-mapping / E1303 **Message emitted:** **Expected mapping for format string, not %s** **Description:** *Used when a format string that uses named conversion specifiers is used with an argument that is not a mapping.* **Problematic code:** ``` print("%(x)d %(y)d" % [1, 2]) # [format-needs-mapping] ``` **Correct code:** ``` print("%(x)d %(y)d" % {"x": 1, "y": 2}) ``` Created by the string \ checker. ### function-redefined / E0102 **Message emitted:** **%s already defined line %s** **Description:** *Used when a function / class / method is redefined.* **Problematic code:** ``` def get_email(): pass def get_email(): # [function-redefined] pass ``` **Correct code:** ``` def get_email(): pass ``` Created by the basic \ checker. ### inconsistent-mro / E0240 **Message emitted:** **Inconsistent method resolution order for class %r** **Description:** *Used when a class has an inconsistent method resolution order.* **Problematic code:** ``` class A: pass class B(A): pass class C(A, B): # [inconsistent-mro] pass ``` **Correct code:** ``` class A: pass class B(A): pass class C(B): # or 'B, A' or 'A' but not 'A, B' pass ``` Created by the classes \ checker. ### inherit-non-class / E0239 **Message emitted:** **Inheriting %r, which is not a class.** **Description:** *Used when a class inherits from something which is not a class.* **Problematic code:** ``` class Fruit(bool): # [inherit-non-class] pass ``` **Correct code:** ``` class Fruit: def __bool__(self): pass ``` Created by the classes \ checker. ### init-is-generator / E0100 **Message emitted:** **\_\_init\_\_ method is a generator** **Description:** *Used when the special class method \_\_init\_\_ is turned into a generator by a yield in its body.* **Problematic code:** ``` class Fruit: def __init__(self, worms): # [init-is-generator] yield from worms apple = Fruit(["Fahad", "Anisha", "Tabatha"]) ``` **Correct code:** ``` class Fruit: def __init__(self, worms): self.__worms = worms def worms(self): yield from self.__worms apple = Fruit(["Fahad", "Anisha", "Tabatha"]) for worm in apple.worms(): pass ``` Created by the basic \ checker. ### invalid-all-format / E0605 **Message emitted:** **Invalid format for \_\_all\_\_, must be tuple or list** **Description:** *Used when \_\_all\_\_ has an invalid format.* **Problematic code:** ``` __all__ = "CONST" # [invalid-all-format] CONST = 42 ``` **Correct code:** ``` __all__ = ("CONST",) CONST = 42 ``` Created by the variables \ checker. ### invalid-all-object / E0604 **Message emitted:** **Invalid object %r in \_\_all\_\_, must contain only strings** **Description:** *Used when an invalid (non-string) object occurs in \_\_all\_\_.* **Problematic code:** ``` __all__ = ( None, # [invalid-all-object] Fruit, Worm, ) class Fruit: pass class Worm: pass ``` **Correct code:** ``` __all__ = ["Fruit", "Worm"] class Fruit: pass class Worm: pass ``` **Additional details:** - **From The Python Language Reference – The import statement \:** "The *public names* defined by a module are determined by checking the module's namespace for a variable named **\_\_all\_\_**; if defined, it must be a sequence of strings which are names defined or imported by that module." **Related links:** - • PEP 8 – Style Guide for Python Code \ Created by the variables \ checker. ### invalid-bool-returned / E0304 **Message emitted:** **\_\_bool\_\_ does not return bool** **Description:** *Used when a \_\_bool\_\_ method returns something which is not a bool* **Problematic code:** ``` class CustomBool: """__bool__ returns an int""" def __bool__(self): # [invalid-bool-returned] return 1 ``` **Correct code:** ``` class CustomBool: """__bool__ returns `bool`""" def __bool__(self): return True ``` Created by the classes \ checker. ### invalid-bytes-returned / E0308 **Message emitted:** **\_\_bytes\_\_ does not return bytes** **Description:** *Used when a \_\_bytes\_\_ method returns something which is not bytes* **Problematic code:** ``` class CustomBytes: """__bytes__ returns """ def __bytes__(self): # [invalid-bytes-returned] return "123" ``` **Correct code:** ``` class CustomBytes: """__bytes__ returns """ def __bytes__(self): return b"some bytes" ``` Created by the classes \ checker. ### invalid-character-backspace / E2510 **Message emitted:** **Invalid unescaped character backspace, use "\\b" instead.** **Description:** *Moves the cursor back, so the character after it will overwrite the character before.* **Problematic code:** ``` STRING = "Invalid character backspace " # [invalid-character-backspace] ``` **Correct code:** ``` STRING = "Valid character backspace \b" ``` Created by the unicode\_checker \ checker. ### invalid-character-carriage-return / E2511 **Message emitted:** **Invalid unescaped character carriage-return, use "\\r" instead.** **Description:** *Moves the cursor to the start of line, subsequent characters overwrite the start of the line.* **Correct code:** ``` STRING = "Valid carriage return: \r" ``` **Additional details:** This message exists because one of our checkers is very generic, but it's never going to raise during normal use as it's a **syntax-error** that would prevent the python ast (and thus pylint) from constructing a code representation of the file. You could encounter it by feeding a properly constructed node directly to the checker. Created by the unicode\_checker \ checker. ### invalid-character-esc / E2513 **Message emitted:** **Invalid unescaped character esc, use "\\x1B" instead.** **Description:** *Commonly initiates escape codes which allow arbitrary control of the terminal.* **Problematic code:** ``` STRING = "Invalid escape character " # [invalid-character-esc] ``` **Correct code:** ``` STRING = "Valid escape character \x1b" ``` Created by the unicode\_checker \ checker. ### invalid-character-nul / E2514 **Message emitted:** **Invalid unescaped character nul, use "\\0" instead.** **Description:** *Mostly end of input for python.* **Additional details:** There's no need to use end-of-string characters. String objects maintain their own length. **Related links:** - • Null terminator in python \ Created by the unicode\_checker \ checker. ### invalid-character-sub / E2512 **Message emitted:** **Invalid unescaped character sub, use "\\x1A" instead.** **Description:** *Ctrl+Z "End of text" on Windows. Some programs (such as type) ignore the rest of the file after it.* **Problematic code:** ``` STRING = "Invalid character sub " # [invalid-character-sub] ``` **Correct code:** ``` STRING = "Valid character sub x1A" ``` Created by the unicode\_checker \ checker. ### invalid-character-zero-width-space / E2515 **Message emitted:** **Invalid unescaped character zero-width-space, use "\\u200B" instead.** **Description:** *Invisible space character could hide real code execution.* **Problematic code:** ``` STRING = "Invalid character zero-width-space ​" # [invalid-character-zero-width-space] ``` **Correct code:** ``` STRING = "Valid character zero-width-space u200B" ``` Created by the unicode\_checker \ checker. ### invalid-class-object / E0243 **Message emitted:** **Invalid assignment to '\_\_class\_\_'. Should be a class definition but got a '%s'** **Description:** *Used when an invalid object is assigned to a \_\_class\_\_ property. Only a class is permitted.* **Problematic code:** ``` class Apple: pass Apple.__class__ = 1 # [invalid-class-object] ``` **Correct code:** ``` class Apple: pass class RedDelicious: pass Apple.__class__ = RedDelicious ``` Created by the classes \ checker. ### invalid-enum-extension / E0244 **Message emitted:** **Extending inherited Enum class "%s"** **Description:** *Used when a class tries to extend an inherited Enum class. Doing so will raise a TypeError at runtime.* **Problematic code:** ``` from enum import Enum class Color(Enum): ORANGE = 1 CHERRY = 2 class Fruit(Color): # [invalid-enum-extension] APPLE = 3 ``` **Correct code:** ``` from enum import Enum class Color(Enum): ORANGE = 1 CHERRY = 2 class Fruit(Enum): ORANGE = 1 CHERRY = 2 APPLE = 3 ``` Created by the classes \ checker. ### invalid-envvar-value / E1507 **Message emitted:** **%s does not support %s type argument** **Description:** *Env manipulation functions support only string type arguments. See https://docs.python.org/3/library/os.html#os.getenv.* **Problematic code:** ``` import os os.getenv(1) # [invalid-envvar-value] ``` **Correct code:** ``` import os os.getenv("1") ``` Created by the stdlib \ checker. ### invalid-field-call / E3701 **Message emitted:** **Invalid usage of field(), %s** **Description:** *The dataclasses.field() specifier should only be used as the value of an assignment within a dataclass, or within the make\_dataclass() function.* **Problematic code:** ``` from dataclasses import dataclass, field @dataclass class C: a: float b: float c: float field(init=False) # [invalid-field-call] def __post_init__(self): self.c = self.a + self.b print(field(init=False)) # [invalid-field-call] ``` **Correct code:** ``` from dataclasses import dataclass, field, make_dataclass C = make_dataclass( "C", [("x", int), "y", ("z", int, field(default=5))], namespace={"add_one": lambda self: self.x + 1}, ) @dataclass class C: a: float b: float c: float = field(init=False) def __post_init__(self): self.c = self.a + self.b ``` Created by the dataclass \ checker. ### invalid-format-returned / E0311 **Message emitted:** **\_\_format\_\_ does not return str** **Description:** *Used when a \_\_format\_\_ method returns something which is not a string* **Problematic code:** ``` class CustomFormat: """__format__ returns """ def __format__(self, format_spec): # [invalid-format-returned] return 1 ``` **Correct code:** ``` class CustomFormat: """__format__ returns """ def __format__(self, format_spec): return "hello!" ``` Created by the classes \ checker. ### invalid-getnewargs-ex-returned / E0313 **Message emitted:** **\_\_getnewargs\_ex\_\_ does not return a tuple containing (tuple, dict)** **Description:** *Used when a \_\_getnewargs\_ex\_\_ method returns something which is not of the form tuple(tuple, dict)* **Problematic code:** ``` class CustomGetNewArgsEx: """__getnewargs_ex__ returns tuple with incorrect arg length""" def __getnewargs_ex__(self): # [invalid-getnewargs-ex-returned] return (tuple(1), dict(x="y"), 1) ``` **Correct code:** ``` class CustomGetNewArgsEx: """__getnewargs_ex__ returns """ def __getnewargs_ex__(self): return ((1,), {"2": 2}) ``` Created by the classes \ checker. ### invalid-getnewargs-returned / E0312 **Message emitted:** **\_\_getnewargs\_\_ does not return a tuple** **Description:** *Used when a \_\_getnewargs\_\_ method returns something which is not a tuple* **Problematic code:** ``` class CustomGetNewArgs: """__getnewargs__ returns an integer""" def __getnewargs__(self): # [invalid-getnewargs-returned] return 1 ``` **Correct code:** ``` class CustomGetNewArgs: """__getnewargs__ returns """ def __getnewargs__(self): return (1, 2) ``` Created by the classes \ checker. ### invalid-hash-returned / E0309 **Message emitted:** **\_\_hash\_\_ does not return int** **Description:** *Used when a \_\_hash\_\_ method returns something which is not an integer* **Problematic code:** ``` class CustomHash: """__hash__ returns dict""" def __hash__(self): # [invalid-hash-returned] return {} ``` **Correct code:** ``` class CustomHash: """__hash__ returns `int`""" def __hash__(self): return 19 ``` Created by the classes \ checker. ### invalid-index-returned / E0305 **Message emitted:** **\_\_index\_\_ does not return int** **Description:** *Used when an \_\_index\_\_ method returns something which is not an integer* **Problematic code:** ``` class CustomIndex: """__index__ returns a dict""" def __index__(self): # [invalid-index-returned] return {"19": "19"} ``` **Correct code:** ``` class CustomIndex: """__index__ returns """ def __index__(self): return 19 ``` Created by the classes \ checker. ### invalid-length-hint-returned / E0310 **Message emitted:** **\_\_length\_hint\_\_ does not return non-negative integer** **Description:** *Used when a \_\_length\_hint\_\_ method returns something which is not a non-negative integer* **Problematic code:** ``` class CustomLengthHint: """__length_hint__ returns non-int""" def __length_hint__(self): # [invalid-length-hint-returned] return 3.0 ``` **Correct code:** ``` class CustomLengthHint: """__length_hint__ returns """ def __length_hint__(self): return 10 ``` Created by the classes \ checker. ### invalid-length-returned / E0303 **Message emitted:** **\_\_len\_\_ does not return non-negative integer** **Description:** *Used when a \_\_len\_\_ method returns something which is not a non-negative integer* **Problematic code:** ``` class FruitBasket: def __init__(self, fruits): self.fruits = ["Apple", "Banana", "Orange"] def __len__(self): # [invalid-length-returned] return -len(self.fruits) ``` **Correct code:** ``` class FruitBasket: def __init__(self, fruits): self.fruits = ["Apple", "Banana", "Orange"] def __len__(self): return len(self.fruits) ``` Created by the classes \ checker. ### invalid-match-args-definition / E1902 **Message emitted:** **\`\_\_match\_args\_\_\` must be a tuple of strings.** **Description:** *Emitted if \`\_\_match\_args\_\_\` isn't a tuple of strings required for match.* **Problematic code:** ``` class Book: __match_args__ = ["title", "year"] # [invalid-match-args-definition] def __init__(self, title, year): self.title = title self.year = year ``` **Correct code:** ``` class Book: __match_args__ = ("title", "year") def __init__(self, title, year): self.title = title self.year = year ``` **Related links:** - • Python documentation \ Created by the match\_statements \ checker. ### invalid-metaclass / E1139 **Message emitted:** **Invalid metaclass %r used** **Description:** *Emitted whenever we can detect that a class is using, as a metaclass, something which might be invalid for using as a metaclass.* **Problematic code:** ``` class Apple(metaclass=int): # [invalid-metaclass] pass ``` **Correct code:** ``` class Plant: pass class Apple(Plant): pass ``` Created by the typecheck \ checker. ### invalid-repr-returned / E0306 **Message emitted:** **\_\_repr\_\_ does not return str** **Description:** *Used when a \_\_repr\_\_ method returns something which is not a string* **Problematic code:** ``` class CustomRepr: """__repr__ returns """ def __repr__(self): # [invalid-repr-returned] return 1 ``` **Correct code:** ``` class CustomRepr: """__repr__ returns """ def __repr__(self): return "apples" ``` Created by the classes \ checker. ### invalid-sequence-index / E1126 **Message emitted:** **Sequence index is not an int, slice, or instance with \_\_index\_\_** **Description:** *Used when a sequence type is indexed with an invalid type. Valid types are ints, slices, and objects with an \_\_index\_\_ method.* **Problematic code:** ``` fruits = ["apple", "banana", "orange"] print(fruits["apple"]) # [invalid-sequence-index] ``` **Correct code:** ``` fruits = ["apple", "banana", "orange"] print(fruits[0]) ``` **Additional details:** Be careful with **\[True\]** or **\[False\]** as sequence index, since **True** and **False** will respectively be evaluated as **1** and **0** and will bring the second element of the list and the first without erroring. Created by the typecheck \ checker. ### invalid-slice-index / E1127 **Message emitted:** **Slice index is not an int, None, or instance with \_\_index\_\_** **Description:** *Used when a slice index is not an integer, None, or an object with an \_\_index\_\_ method.* **Problematic code:** ``` LETTERS = ["a", "b", "c", "d"] FIRST_THREE = LETTERS[:"3"] # [invalid-slice-index] ``` **Correct code:** ``` LETTERS = ["a", "b", "c", "d"] FIRST_THREE = LETTERS[:3] ``` Created by the typecheck \ checker. ### invalid-slice-step / E1144 **Message emitted:** **Slice step cannot be 0** **Description:** *Used when a slice step is 0 and the object doesn't implement a custom \_\_getitem\_\_ method.* **Problematic code:** ``` LETTERS = ["a", "b", "c", "d"] LETTERS[::0] # [invalid-slice-step] ``` **Correct code:** ``` LETTERS = ["a", "b", "c", "d"] LETTERS[::2] ``` Created by the typecheck \ checker. ### invalid-slots / E0238 **Message emitted:** **Invalid \_\_slots\_\_ object** **Description:** *Used when an invalid \_\_slots\_\_ is found in class. Only a string, an iterable or a sequence is permitted.* **Problematic code:** ``` class Person: # [invalid-slots] __slots__ = 42 ``` **Correct code:** ``` class Person: __slots__ = ("name", "age") ``` Created by the classes \ checker. ### invalid-slots-object / E0236 **Message emitted:** **Invalid object %r in \_\_slots\_\_, must contain only non empty strings** **Description:** *Used when an invalid (non-string) object occurs in \_\_slots\_\_.* **Problematic code:** ``` class Person: __slots__ = ("name", 3) # [invalid-slots-object] ``` **Correct code:** ``` class Person: __slots__ = ("name", "surname") ``` **Related links:** - • Documentation for \_\_slots\_\_ \ Created by the classes \ checker. ### invalid-star-assignment-target / E0113 **Message emitted:** **Starred assignment target must be in a list or tuple** **Description:** *Emitted when a star expression is used as a starred assignment target.* **Problematic code:** ``` *fruit = ["apple", "banana", "orange"] # [invalid-star-assignment-target] ``` **Correct code:** ``` fruit = ["apple", "banana", "orange"] ``` Created by the basic \ checker. ### invalid-str-returned / E0307 **Message emitted:** **\_\_str\_\_ does not return str** **Description:** *Used when a \_\_str\_\_ method returns something which is not a string* **Problematic code:** ``` class CustomStr: """__str__ returns int""" def __str__(self): # [invalid-str-returned] return 1 ``` **Correct code:** ``` class CustomStr: """__str__ returns """ def __str__(self): return "oranges" ``` Created by the classes \ checker. ### invalid-unary-operand-type / E1130 **Message emitted:** **%s** **Description:** *Emitted when a unary operand is used on an object which does not support this type of operation.* **Problematic code:** ``` cherries = 10 eaten_cherries = int cherries = -eaten_cherries # [invalid-unary-operand-type] ``` **Correct code:** ``` cherries = 10 eaten_cherries = 2 cherries -= eaten_cherries ``` Created by the typecheck \ checker. ### invalid-unicode-codec / E2501 **Message emitted:** **UTF-16 and UTF-32 aren't backward compatible. Use UTF-8 instead** **Description:** *For compatibility use UTF-8 instead of UTF-16/UTF-32. See also https://bugs.python.org/issue1503789 for a history of this issue. And https://softwareengineering.stackexchange.com/questions/102205/ for some possible problems when using UTF-16 for instance.* **Additional details:** This message is a placeholder for a potential future issue with unicode codecs. Created by the unicode\_checker \ checker. ### logging-format-truncated / E1201 **Message emitted:** **Logging format string ends in middle of conversion specifier** **Description:** *Used when a logging statement format string terminates before the end of a conversion specifier.* **Problematic code:** ``` import logging import sys logging.warning("Python version: %", sys.version) # [logging-format-truncated] ``` **Correct code:** ``` import logging import sys logging.warning("Python version: %s", sys.version) ``` Created by the logging \ checker. ### logging-too-few-args / E1206 **Message emitted:** **Not enough arguments for logging format string** **Description:** *Used when a logging format string is given too few arguments.* **Problematic code:** ``` import logging try: function() except Exception as e: logging.error("%s error occurred: %s", e) # [logging-too-few-args] raise ``` **Correct code:** ``` import logging try: function() except Exception as e: logging.error("%s error occurred: %s", type(e), e) raise ``` Created by the logging \ checker. ### logging-too-many-args / E1205 **Message emitted:** **Too many arguments for logging format string** **Description:** *Used when a logging format string is given too many arguments.* **Problematic code:** ``` import logging try: function() except Exception as e: logging.error("Error occurred: %s", type(e), e) # [logging-too-many-args] raise ``` **Correct code:** ``` import logging try: function() except Exception as e: logging.error("%s error occurred: %s", type(e), e) raise ``` Created by the logging \ checker. ### logging-unsupported-format / E1200 **Message emitted:** **Unsupported logging format character %r (%#02x) at index %d** **Description:** *Used when an unsupported format character is used in a logging statement format string.* **Problematic code:** ``` import logging logging.info("%s %y !", "Hello", "World") # [logging-unsupported-format] ``` **Correct code:** ``` import logging logging.info("%s %s !", "Hello", "World") ``` Created by the logging \ checker. ### method-hidden / E0202 **Message emitted:** **An attribute defined in %s line %s hides this method** **Description:** *Used when a class defines a method which is hidden by an instance attribute from an ancestor class or set by some client code.* **Problematic code:** ``` class Fruit: def __init__(self, vitamins): self.vitamins = vitamins def vitamins(self): # [method-hidden] pass ``` **Correct code:** ``` class Fruit: def __init__(self, vitamins): self.vitamins = vitamins def antioxidants(self): pass ``` Created by the classes \ checker. ### misplaced-bare-raise / E0704 **Message emitted:** **The raise statement is not inside an except clause** **Description:** *Used when a bare raise is not used inside an except clause. This generates an error, since there are no active exceptions to be reraised. An exception to this rule is represented by a bare raise inside a finally clause, which might work, as long as an exception is raised inside the try block, but it is nevertheless a code smell that must not be relied upon.* **Problematic code:** ``` def validate_positive(x): if x <= 0: raise # [misplaced-bare-raise] ``` **Correct code:** ``` def validate_positive(x): if x <= 0: raise ValueError(f"{x} is not positive") ``` Created by the exceptions \ checker. ### misplaced-format-function / E0119 **Message emitted:** **format function is not called on str** **Description:** *Emitted when format function is not called on str object. e.g doing print("value: {}").format(123) instead of print("value: {}".format(123)). This might not be what the user intended to do.* **Problematic code:** ``` print("Value: {}").format("Car") # [misplaced-format-function] ``` **Correct code:** ``` print("Value: {}".format("Car")) ``` Created by the basic \ checker. ### missing-format-string-key / E1304 **Message emitted:** **Missing key %r in format string dictionary** **Description:** *Used when a format string that uses named conversion specifiers is used with a dictionary that doesn't contain all the keys required by the format string.* **Problematic code:** ``` # +1: [missing-format-string-key] fruit_prices = """ Apple: %(apple_price)d ¤ Orange: %(orange_price)d ¤ """ % { "apple_price": 42 } ``` **Correct code:** ``` fruit_prices = """ Apple: %(apple_price)d ¤ Orange: %(orange_price)d ¤ """ % { "apple_price": 42, "orange_price": 87, } ``` Created by the string \ checker. ### missing-kwoa / E1125 **Message emitted:** **Missing mandatory keyword argument %r in %s call** **Description:** *Used when a function call does not pass a mandatory keyword-only argument.* **Problematic code:** ``` def target(pos, *, keyword): return pos + keyword def not_forwarding_kwargs(*args, **kwargs): target(*args) # [missing-kwoa] ``` **Correct code:** ``` def target(pos, *, keyword): return pos + keyword def not_forwarding_kwargs(*args, **kwargs): target(*args, **kwargs) ``` Created by the typecheck \ checker. ### mixed-format-string / E1302 **Message emitted:** **Mixing named and unnamed conversion specifiers in format string** **Description:** *Used when a format string contains both named (e.g. '%(foo)d') and unnamed (e.g. '%d') conversion specifiers. This is also used when a named conversion specifier contains \* for the minimum field width and/or precision.* **Problematic code:** ``` print("x=%(x)d, y=%d" % (0, 1)) # [mixed-format-string] ``` **Correct code:** **only\_named.py**: ``` print("x=%(x)d, y=%(y)d" % {"x": 0, "y": 1}) ``` **only\_ordered.py**: ``` print("x=%d, y=%d" % (0, 1)) ``` Created by the string \ checker. ### modified-iterating-dict / E4702 **Message emitted:** **Iterated dict '%s' is being modified inside for loop body, iterate through a copy of it instead.** **Description:** *Emitted when items are added or removed to a dict being iterated through. Doing so raises a RuntimeError.* **Problematic code:** ``` fruits = {"apple": 1, "orange": 2, "mango": 3} i = 0 for fruit in fruits: fruits["apple"] = i # [modified-iterating-dict] i += 1 ``` **Correct code:** ``` fruits = {"apple": 1, "orange": 2, "mango": 3} i = 0 for fruit in fruits.copy(): fruits["apple"] = i i += 1 ``` Created by the modified\_iteration \ checker. ### modified-iterating-set / E4703 **Message emitted:** **Iterated set '%s' is being modified inside for loop body, iterate through a copy of it instead.** **Description:** *Emitted when items are added or removed to a set being iterated through. Doing so raises a RuntimeError.* **Problematic code:** ``` fruits = {"apple", "orange", "mango"} for fruit in fruits: fruits.add(fruit + "yum") # [modified-iterating-set] ``` **Correct code:** ``` fruits = {"apple", "orange", "mango"} for fruit in fruits.copy(): fruits.add(fruit + "yum") ``` Created by the modified\_iteration \ checker. ### multiple-class-sub-patterns / E1904 **Message emitted:** **Multiple sub-patterns for attribute %s** **Description:** *Emitted when there is more than one sub-pattern for a specific attribute in a class pattern.* **Problematic code:** ``` class Book: __match_args__ = ("title", "year") def __init__(self, title, year): self.title = title self.year = year def func(item: Book): match item: case Book("abc", title="abc"): # [multiple-class-sub-patterns] ... case Book(year=2000, year=2001): # [multiple-class-sub-patterns] ... ``` **Correct code:** ``` class Book: __match_args__ = ("title", "year") def __init__(self, title, year): self.title = title self.year = year def func(item: Book): match item: case Book(title="abc"): ... case Book(year=2000): ... ``` **Related links:** - • Python documentation \ Created by the match\_statements \ checker. ### no-member / E1101 **Message emitted:** **%s %r has no %r member%s** **Description:** *Used when a variable is accessed for a nonexistent member.* **Problematic code:** ``` from pathlib import Path directories = Path(".").mothers # [no-member] class Cat: def meow(self): print("Meow") Cat().roar() # [no-member] ``` **Correct code:** ``` from pathlib import Path directories = Path(".").parents class Cat: def meow(self): print("Meow") Cat().meow() ``` **Additional details:** If you are getting the dreaded **no-member** error, there is a possibility that either: - • pylint found a bug in your code - • You're launching pylint without the dependencies installed in its environment - • pylint would need to lint a C extension module and is refraining to do so - • pylint does not understand dynamically generated code Linting C extension modules is not supported out of the box, especially since pylint has no way to get an AST object out of the extension module. But pylint actually has a mechanism which you might use in case you want to analyze C extensions. Pylint has a flag, called **extension-pkg-allow-list** (formerly **extension-pkg-whitelist**), through which you can tell it to import that module and to build an AST from that imported module: ``` $ pylint --extension-pkg-allow-list=your_c_extension ``` Be aware though that using this flag means that extensions are loaded into the active Python interpreter and may run arbitrary code, which you may not want. This is the reason why we disable by default loading C extensions. In case you do not want the hassle of passing C extensions module with this flag all the time, you can enable **unsafe-load-any-extension** in your configuration file, which will build AST objects from all the C extensions that pylint encounters: ``` $ pylint --unsafe-load-any-extension=y ``` Alternatively, since pylint emits a separate error for attributes that cannot be found in C extensions, **c-extension-no-member**, you can disable this error for your project. If something is generated dynamically, pylint won't be able to understand the code from your library (c-extension or not). You can then specify generated attributes with the **generated-members** option. For example if **cv2.LINE\_AA** and **sphinx.generated\_member** create false positives for **no-member**, you can do: ``` $ pylint --generated-member=cv2.LINE_AA,sphinx.generated_member ``` Created by the typecheck \ checker. ### no-method-argument / E0211 **Message emitted:** **Method %r has no argument** **Description:** *Used when a method which should have the bound instance as first argument has no argument defined.* **Problematic code:** ``` class Person: def print_greeting(): # [no-method-argument] print("hello") ``` **Correct code:** ``` class Person: def print_greeting(self): print("hello") ``` Created by the classes \ checker. ### no-name-in-module / E0611 **Message emitted:** **No name %r in module %r** **Description:** *Used when a name cannot be found in a module.* **Problematic code:** ``` from os import pizza # [no-name-in-module] ``` **Correct code:** ``` from os import path ``` Created by the variables \ checker. ### no-self-argument / E0213 **Message emitted:** **Method %r should have "self" as first argument** **Description:** *Used when a method has an attribute different the "self" as first argument. This is considered as an error since this is a so common convention that you shouldn't break it!* **Problematic code:** ``` class Fruit: def __init__(this, name): # [no-self-argument] this.name = name ``` **Correct code:** ``` class Fruit: def __init__(self, name): self.name = name ``` Created by the classes \ checker. ### no-value-for-parameter / E1120 **Message emitted:** **No value for argument %s in %s call** **Description:** *Used when a function call passes too few arguments.* **Problematic code:** ``` def add(x, y): return x + y add(1) # [no-value-for-parameter] ``` **Correct code:** ``` def add(x, y): return x + y add(1, 2) ``` Created by the typecheck \ checker. ### non-iterator-returned / E0301 **Message emitted:** **\_\_iter\_\_ returns non-iterator** **Description:** *Used when an \_\_iter\_\_ method returns something which is not an iterable (i.e. has no \`\_\_next\_\_\` method)* **Problematic code:** ``` import random class GenericAstrology: def __init__(self, signs, predictions): self.signs = signs self.predictions = predictions def __iter__(self): # [non-iterator-returned] self.index = 0 self.number_of_prediction = len(self.predictions) return self SIGNS = ["Aries", "Taurus", "Gemini", "Cancer", "Leo", "Virgo", "Libra"] PREDICTIONS = ["good things", "bad thing", "existential dread"] for sign, prediction in GenericAstrology(SIGNS, PREDICTIONS): print(f"{sign} : {prediction} today") ``` **Correct code:** ``` import random class GenericAstrology: def __init__(self, signs, predictions): self.signs = signs self.predictions = predictions def __iter__(self): self.index = 0 self.number_of_prediction = len(self.predictions) return self def __next__(self): if self.index == len(self.signs): raise StopIteration self.index += 1 prediction_index = random.randint(0, self.number_of_prediction - 1) return self.signs[self.index - 1], self.predictions[prediction_index] SIGNS = ["Aries", "Taurus", "Gemini", "Cancer", "Leo", "Virgo", "Libra"] PREDICTIONS = ["good things", "bad thing", "existential dread"] for sign, prediction in GenericAstrology(SIGNS, PREDICTIONS): print(f"{sign} : {prediction} today") ``` Created by the classes \ checker. ### nonexistent-operator / E0107 **Message emitted:** **Use of the non-existent %s operator** **Description:** *Used when you attempt to use the C-style pre-increment or pre-decrement operator -- and ++, which doesn't exist in Python.* **Problematic code:** ``` i = 0 while i <= 10: print(i) ++i # [nonexistent-operator] ``` **Correct code:** ``` i = 0 while i <= 10: print(i) i += 1 ``` Created by the basic \ checker. ### nonlocal-and-global / E0115 **Message emitted:** **Name %r is nonlocal and global** **Description:** *Emitted when a name is both nonlocal and global.* **Problematic code:** ``` NUMBER = 42 def update_number(number): # [nonlocal-and-global] global NUMBER nonlocal NUMBER NUMBER = number print(f"New global number is: {NUMBER}") update_number(24) ``` **Correct code:** ``` NUMBER = 42 def update_number(number): global NUMBER NUMBER = number print(f"New global number is: {NUMBER}") update_number(24) ``` Created by the basic \ checker. ### nonlocal-without-binding / E0117 **Message emitted:** **nonlocal name %s found without binding** **Description:** *Emitted when a nonlocal variable does not have an attached name somewhere in the parent scopes* **Problematic code:** ``` class Fruit: def get_color(self): nonlocal colors # [nonlocal-without-binding] ``` **Correct code:** ``` class Fruit: colors = ["red", "green"] def get_color(self): nonlocal colors ``` Created by the basic \ checker. ### not-a-mapping / E1134 **Message emitted:** **Non-mapping value %s is used in a mapping context** **Description:** *Used when a non-mapping value is used in place where mapping is expected* **Problematic code:** ``` def print_colors(**colors): print(colors) print_colors(**list("red", "black")) # [not-a-mapping] ``` **Correct code:** ``` def print_colors(**colors): print(colors) print_colors(**dict(red=1, black=2)) ``` Created by the typecheck \ checker. ### not-an-iterable / E1133 **Message emitted:** **Non-iterable value %s is used in an iterating context** **Description:** *Used when a non-iterable value is used in place where iterable is expected* **Problematic code:** ``` for i in 10: # [not-an-iterable] pass ``` **Correct code:** ``` for i in "10": pass ``` Created by the typecheck \ checker. ### not-async-context-manager / E1701 **Message emitted:** **Async context manager '%s' doesn't implement \_\_aenter\_\_ and \_\_aexit\_\_.** **Description:** *Used when an async context manager is used with an object that does not implement the async context management protocol.* **Problematic code:** ``` class ContextManager: def __enter__(self): pass def __exit__(self, *exc): pass async def foo(): async with ContextManager(): # [not-async-context-manager] pass ``` **Correct code:** ``` class AsyncContextManager: def __aenter__(self): pass def __aexit__(self, *exc): pass async def foo(): async with AsyncContextManager(): pass ``` **Additional details:** Async context manager doesn't implement **\_\_aenter\_\_** and **\_\_aexit\_\_**. It can't be emitted when using Python \< 3.5. Created by the async \ checker. ### not-callable / E1102 **Message emitted:** **%s is not callable** **Description:** *Used when an object being called has been inferred to a non callable object.* **Problematic code:** ``` NUMBER = 42 print(NUMBER()) # [not-callable] ``` **Correct code:** ``` NUMBER = 42 print(NUMBER) ``` Created by the typecheck \ checker. ### not-context-manager / E1129 **Message emitted:** **Context manager '%s' doesn't implement \_\_enter\_\_ and \_\_exit\_\_.** **Description:** *Used when an instance in a with statement doesn't implement the context manager protocol(\_\_enter\_\_/\_\_exit\_\_).* **Problematic code:** ``` class MyContextManager: def __enter__(self): pass with MyContextManager() as c: # [not-context-manager] pass ``` **Correct code:** ``` class MyContextManager: def __enter__(self): pass def __exit__(self, *exc): pass with MyContextManager() as c: pass ``` Created by the typecheck \ checker. ### not-in-loop / E0103 **Message emitted:** **%r not properly in loop** **Description:** *Used when break or continue keywords are used outside a loop.* **Problematic code:** ``` def print_even_numbers(): for i in range(100): if i % 2 == 0: print(i) else: continue # [not-in-loop] ``` **Correct code:** ``` def print_even_numbers(): for i in range(100): if i % 2: continue print(i) ``` Created by the basic \ checker. ### notimplemented-raised / E0711 **Message emitted:** **NotImplemented raised - should raise NotImplementedError** **Description:** *Used when NotImplemented is raised instead of NotImplementedError* **Problematic code:** ``` class Worm: def bore(self): raise NotImplemented # [notimplemented-raised] ``` **Correct code:** ``` class Worm: def bore(self): raise NotImplementedError ``` Created by the exceptions \ checker. ### positional-only-arguments-expected / E3102 **Message emitted:** **\`%s()\` got some positional-only arguments passed as keyword arguments: %s** **Description:** *Emitted when positional-only arguments have been passed as keyword arguments. Remove the keywords for the affected arguments in the function call.* **Problematic code:** ``` def cube(n, /): """Takes in a number n, returns the cube of n""" return n**3 cube(n=2) # [positional-only-arguments-expected] ``` **Correct code:** ``` def cube(n, /): """Takes in a number n, returns the cube of n""" return n**3 cube(2) ``` **Related links:** - • PEP 570 \ Created by the method\_args \ checker. ### possibly-used-before-assignment / E0606 **Message emitted:** **Possibly using variable %r before assignment** **Description:** *Emitted when a local variable is accessed before its assignment took place in both branches of an if/else switch.* **Problematic code:** ``` def check_lunchbox(items: list[str]): if not items: empty = True print(empty) # [possibly-used-before-assignment] ``` **Correct code:** ``` def check_lunchbox(items: list[str]): empty = False if not items: empty = True print(empty) ``` **Additional details:** You can use **assert\_never** to mark exhaustive choices: ``` from typing import assert_never def handle_date_suffix(suffix): if suffix == "d": ... elif suffix == "m": ... elif suffix == "y": ... else: assert_never(suffix) if suffix in "dmy": handle_date_suffix(suffix) ``` Or, instead of *assert\_never()*, you can call a function with a return annotation of *Never* or *NoReturn*. Unlike in the general case, where by design pylint ignores type annotations and does its own static analysis, here, pylint treats these special annotations like a disable comment. Pylint currently allows repeating the same test like this, even though this lets some error cases through, as pylint does not assess the intervening code: ``` if guarded(): var = 1 # what if code here affects the result of guarded()? if guarded(): print(var) ``` But this exception is limited to the repeating the exact same test. This warns: ``` if guarded(): var = 1 if guarded() or other_condition: print(var) # [possibly-used-before-assignment] ``` If you find this surprising, consider that pylint, as a static analysis tool, does not know if **guarded()** is deterministic or talks to a database. For variables (e.g. **guarded** versus **guarded()**), this is less of an issue, so in this case, **possibly-used-before-assignment** acts more like a future-proofing style preference than an error, per se. Created by the variables \ checker. ### potential-index-error / E0643 **Message emitted:** **Invalid index for iterable length** **Description:** *Emitted when an index used on an iterable goes beyond the length of that iterable.* **Problematic code:** ``` print([1, 2, 3][3]) # [potential-index-error] ``` **Correct code:** ``` print([1, 2, 3][2]) ``` Created by the variables \ checker. ### raising-bad-type / E0702 **Message emitted:** **Raising %s while only classes or instances are allowed** **Description:** *Used when something which is neither a class nor an instance is raised (i.e. a \`TypeError\` will be raised).* **Problematic code:** ``` class FasterThanTheSpeedOfLightError(ZeroDivisionError): def __init__(self): super().__init__("You can't go faster than the speed of light !") def calculate_speed(distance: float, time: float) -> float: try: return distance / time except ZeroDivisionError as e: raise None # [raising-bad-type] ``` **Correct code:** ``` class FasterThanTheSpeedOfLightError(ZeroDivisionError): def __init__(self): super().__init__("You can't go faster than the speed of light !") def calculate_speed(distance: float, time: float) -> float: try: return distance / time except ZeroDivisionError as e: raise FasterThanTheSpeedOfLightError() from e ``` Created by the exceptions \ checker. ### raising-non-exception / E0710 **Message emitted:** **Raising a class which doesn't inherit from BaseException** **Description:** *Used when a class which doesn't inherit from BaseException is raised.* **Problematic code:** ``` raise str # [raising-non-exception] ``` **Correct code:** ``` raise Exception("Goodbye world !") ``` Created by the exceptions \ checker. ### redundant-keyword-arg / E1124 **Message emitted:** **Argument %r passed by position and keyword in %s call** **Description:** *Used when a function call would result in assigning multiple values to a function parameter, one value from a positional argument and one from a keyword argument.* **Problematic code:** ``` def square(x): return x * x square(5, x=4) # [redundant-keyword-arg] ``` **Correct code:** **only\_arg.py**: ``` def square(x): return x * x square(5) ``` **only\_kwarg.py**: ``` def square(x): return x * x square(x=4) ``` Created by the typecheck \ checker. ### relative-beyond-top-level / E0402 **Message emitted:** **Attempted relative import beyond top-level package** **Description:** *Used when a relative import tries to access too many levels in the current package.* **Problematic code:** ``` from ................antigravity import NGField # [relative-beyond-top-level] ``` **Correct code:** **absolute\_import.py**: ``` from physic.antigravity import NGField ``` **fix\_the\_relative\_import.py**: ``` # Right number of dots in the import: you needed 15 dots, not 16, duh. # from ...............antigravity import NGField ``` **Additional details:** Absolute imports were strongly preferred, historically. Relative imports allow you to reorganize packages without changing any code, but these days refactoring tools and IDEs allow you to do that at almost no cost anyway if the imports are explicit/absolute. Therefore, absolute imports are often still preferred over relative ones. **Related links:** - • Absolute vs. explicit relative import of Python module \ - • Withdraw anti-recommendation of relative imports from documentation \ Created by the imports \ checker. ### repeated-keyword / E1132 **Message emitted:** **Got multiple values for keyword argument %r in function call** **Description:** *Emitted when a function call got multiple values for a keyword.* **Problematic code:** ``` def func(a, b, c): return a, b, c func(1, 2, c=3, **{"c": 4}) # [repeated-keyword] func(1, 2, **{"c": 3}, **{"c": 4}) # [repeated-keyword] ``` **Correct code:** ``` def func(a, b, c): return a, b, c func(1, 2, c=3) ``` Created by the typecheck \ checker. ### return-arg-in-generator / E0106 **Message emitted:** **Return with argument inside generator** **Description:** *Used when a "return" statement with an argument is found in a generator function or method (e.g. with some "yield" statements).* **Correct code:** ``` def yield_numbers(): for number in range(10): yield number return "I am now allowed!" # This was not allowed in Python 3.3 and earlier. ``` **Additional details:** This is a message that isn't going to be raised for python \> 3.3. It was raised for code like: ``` def interrogate_until_you_find_jack(pirates): for pirate in pirates: if pirate == "Captain Jack Sparrow": return "Arrr! We've found our captain!" yield pirate ``` Which is now valid and equivalent to the previously expected: ``` def interrogate_until_you_find_jack(pirates): for pirate in pirates: if pirate == "Captain Jack Sparrow": raise StopIteration("Arrr! We've found our captain!") yield pirate ``` **Related links:** - • PEP380 \ - • Stackoverflow explanation \ Created by the basic \ checker. ### return-in-init / E0101 **Message emitted:** **Explicit return in \_\_init\_\_** **Description:** *Used when the special class method \_\_init\_\_ has an explicit return value.* **Problematic code:** ``` class Sum: def __init__(self, a, b): # [return-in-init] return a + b ``` **Correct code:** ``` class Sum: def __init__(self, a, b) -> None: self.result = a + b ``` **Related links:** - • \_\_init\_\_ method documentation \ Created by the basic \ checker. ### return-outside-function / E0104 **Message emitted:** **Return outside function** **Description:** *Used when a "return" statement is found outside a function or method.* **Problematic code:** ``` return 42 # [return-outside-function] ``` **Correct code:** ``` def get_the_answer(): return 42 ``` Created by the basic \ checker. ### singledispatch-method / E1519 **Message emitted:** **singledispatch decorator should not be used with methods, use singledispatchmethod instead.** **Description:** *singledispatch should decorate functions and not class/instance methods. Use singledispatchmethod for those cases.* **Problematic code:** ``` from functools import singledispatch class Board: @singledispatch # [singledispatch-method] def convert_position(self, position): pass @convert_position.register # [singledispatch-method] def _(self, position: str) -> tuple: position_a, position_b = position.split(",") return (int(position_a), int(position_b)) @convert_position.register # [singledispatch-method] def _(self, position: tuple) -> str: return f"{position[0]},{position[1]}" ``` **Correct code:** ``` from functools import singledispatch @singledispatch def convert_position(position): print(position) @convert_position.register def _(position: str) -> tuple: position_a, position_b = position.split(",") return (int(position_a), int(position_b)) @convert_position.register def _(position: tuple) -> str: return f"{position[0]},{position[1]}" ``` Created by the stdlib \ checker. ### singledispatchmethod-function / E1520 **Message emitted:** **singledispatchmethod decorator should not be used with functions, use singledispatch instead.** **Description:** *singledispatchmethod should decorate class/instance methods and not functions. Use singledispatch for those cases.* **Problematic code:** ``` from functools import singledispatchmethod @singledispatchmethod # [singledispatchmethod-function] def convert_position(position): print(position) @convert_position.register # [singledispatchmethod-function] def _(position: str) -> tuple: position_a, position_b = position.split(",") return (int(position_a), int(position_b)) @convert_position.register # [singledispatchmethod-function] def _(position: tuple) -> str: return f"{position[0]},{position[1]}" ``` **Correct code:** ``` from functools import singledispatchmethod class Board: @singledispatchmethod def convert_position(cls, position): pass @singledispatchmethod @classmethod def _(cls, position: str) -> tuple: position_a, position_b = position.split(",") return (int(position_a), int(position_b)) @singledispatchmethod @classmethod def _(cls, position: tuple) -> str: return f"{position[0]},{position[1]}" ``` Created by the stdlib \ checker. ### star-needs-assignment-target / E0114 **Message emitted:** **Can use starred expression only in assignment target** **Description:** *Emitted when a star expression is not used in an assignment target.* **Problematic code:** ``` stars = *["Sirius", "Arcturus", "Vega"] # [star-needs-assignment-target] ``` **Correct code:** ``` sirius, *arcturus_and_vega = ["Sirius", "Arcturus", "Vega"] ``` Created by the basic \ checker. ### syntax-error / E0001 **Message emitted:** **%s** **Description:** *Used when a syntax error is raised for a module.* **Problematic code:** ``` fruit_stock = { 'apple': 42, 'orange': 21 # [syntax-error] 'banana': 12 } ``` **Correct code:** ``` fruit_stock = {"apple": 42, "orange": 21, "banana": 12} ``` **Additional details:** The python's ast builtin module cannot parse your code if there's a syntax error, so if there's a syntax error other messages won't be available at all. **Related links:** - • Why can't pylint recover from a syntax error ? \ Created by the main \ checker. ### too-few-format-args / E1306 **Message emitted:** **Not enough arguments for format string** **Description:** *Used when a format string that uses unnamed conversion specifiers is given too few arguments* **Problematic code:** ``` print("Today is {0}, so tomorrow will be {1}".format("Monday")) # [too-few-format-args] ``` **Correct code:** ``` print("Today is {0}, so tomorrow will be {1}".format("Monday", "Tuesday")) ``` **Related links:** - • String Formatting \ Created by the string \ checker. ### too-many-format-args / E1305 **Message emitted:** **Too many arguments for format string** **Description:** *Used when a format string that uses unnamed conversion specifiers is given too many arguments.* **Problematic code:** ``` # +1: [too-many-format-args] print("Today is {0}, so tomorrow will be {1}".format("Monday", "Tuesday", "Wednesday")) ``` **Correct code:** ``` print("Today is {0}, so tomorrow will be {1}".format("Monday", "Tuesday")) ``` **Related links:** - • String Formatting \ Created by the string \ checker. ### too-many-function-args / E1121 **Message emitted:** **Too many positional arguments for %s call** **Description:** *Used when a function call passes too many positional arguments.* **Problematic code:** ``` class Fruit: def __init__(self, color): self.color = color apple = Fruit("red", "apple", [1, 2, 3]) # [too-many-function-args] ``` **Correct code:** ``` class Fruit: def __init__(self, color, name): self.color = color self.name = name apple = Fruit("red", "apple") ``` Created by the typecheck \ checker. ### too-many-positional-sub-patterns / E1903 **Message emitted:** **%s expects %d positional sub-patterns (given %d)** **Description:** *Emitted when the number of allowed positional sub-patterns exceeds the number of allowed sub-patterns specified in \`\_\_match\_args\_\_\`.* **Problematic code:** ``` class Book: __match_args__ = ("title", "year") def __init__(self, title, year, author): self.title = title self.year = year self.author = author def func(item: Book): match item: case Book("title", 2000, "author"): # [too-many-positional-sub-patterns] ... ``` **Correct code:** ``` class Book: __match_args__ = ("title", "year") def __init__(self, title, year, author): self.title = title self.year = year self.author = author def func(item: Book): match item: case Book("title", 2000, author="author"): ... ``` **Related links:** - • Python documentation \ Created by the match\_statements \ checker. ### too-many-star-expressions / E0112 **Message emitted:** **More than one starred expression in assignment** **Description:** *Emitted when there are more than one starred expressions (\`\*x\`) in an assignment. This is a SyntaxError.* **Problematic code:** ``` *stars, *constellations = ["Sirius", "Arcturus", "Vega"] # [too-many-star-expressions] ``` **Correct code:** ``` *sirius_and_arcturus, vega = ["Sirius", "Arcturus", "Vega"] ``` Created by the basic \ checker. ### truncated-format-string / E1301 **Message emitted:** **Format string ends in middle of conversion specifier** **Description:** *Used when a format string terminates before the end of a conversion specifier.* **Problematic code:** ``` PARG_2 = 1 print("strange format %2" % PARG_2) # [truncated-format-string] ``` **Correct code:** ``` PARG_2 = 1 print(f"strange format {PARG_2}") ``` Created by the string \ checker. ### undefined-all-variable / E0603 **Message emitted:** **Undefined variable name %r in \_\_all\_\_** **Description:** *Used when an undefined variable name is referenced in \_\_all\_\_.* **Problematic code:** ``` __all__ = ["get_fruit_colour"] # [undefined-all-variable] def get_fruit_color(): pass ``` **Correct code:** ``` __all__ = ["get_fruit_color"] def get_fruit_color(): pass ``` **Related links:** - • Importing \* From a Package \ Created by the variables \ checker. ### undefined-variable / E0602 **Message emitted:** **Undefined variable %r** **Description:** *Used when an undefined variable is accessed.* **Problematic code:** ``` print(number + 2) # [undefined-variable] ``` **Correct code:** ``` number = 3 print(number + 2) ``` Created by the variables \ checker. ### unexpected-keyword-arg / E1123 **Message emitted:** **Unexpected keyword argument %r in %s call** **Description:** *Used when a function call passes a keyword argument that doesn't correspond to one of the function's parameter names.* **Problematic code:** ``` def print_coordinates(x=0, y=0): print(f"{x=}, {y=}") print_coordinates(x=1, y=2, z=3) # [unexpected-keyword-arg] ``` **Correct code:** ``` def print_coordinates(x=0, y=0): print(f"{x=}, {y=}") print_coordinates(x=1, y=2) ``` Created by the typecheck \ checker. ### unexpected-special-method-signature / E0302 **Message emitted:** **The special method %r expects %s param(s), %d %s given** **Description:** *Emitted when a special method was defined with an invalid number of parameters. If it has too few or too many, it might not work at all.* **Problematic code:** ``` class ContextManager: def __enter__(self, context): # [unexpected-special-method-signature] pass def __exit__(self, type): # [unexpected-special-method-signature] pass ``` **Correct code:** ``` class ContextManager: def __enter__(self): pass def __exit__(self, type, value, traceback): pass ``` Created by the classes \ checker. ### unhashable-member / E1143 **Message emitted:** **'%s' is unhashable and can't be used as a %s in a %s** **Description:** *Emitted when a dict key or set member is not hashable (i.e. doesn't define \_\_hash\_\_ method).* **Problematic code:** ``` # Print the number of apples: print({"apple": 42}[["apple"]]) # [unhashable-member] ``` **Correct code:** ``` # Print the number of apples: print({"apple": 42}["apple"]) ``` Created by the typecheck \ checker. ### unpacking-non-sequence / E0633 **Message emitted:** **Attempting to unpack a non-sequence%s** **Description:** *Used when something which is not a sequence is used in an unpack assignment* **Problematic code:** ``` a, b, c = 1 # [unpacking-non-sequence] ``` **Correct code:** ``` a, b, c = 1, 2, 3 ``` Created by the variables \ checker. ### unrecognized-inline-option / E0011 **Message emitted:** **Unrecognized file option %r** **Description:** *Used when an unknown inline option is encountered.* **Problematic code:** ``` # +1: [unrecognized-inline-option] # pylint:applesoranges=1 ``` **Correct code:** ``` # pylint: enable=too-many-public-methods ``` Created by the main \ checker. ### unrecognized-option / E0015 **Message emitted:** **Unrecognized option found: %s** **Description:** *Used when we detect an option that we do not recognize.* **Additional details:** One of your options is not recognized. There's nothing to change in your code, but your pylint configuration or the way you launch pylint needs to be modified. For example, this message would be raised when invoking pylint with **pylint --unknown-option=yes test.py**. Or you might be launching pylint with the following **toml** configuration: ``` [tool.pylint] jars = "10" ``` When the following should be used: ``` [tool.pylint] jobs = "10" ``` This warning was released in pylint 2.14: bad options were silently failing before. Created by the main \ checker. ### unsubscriptable-object / E1136 **Message emitted:** **Value '%s' is unsubscriptable** **Description:** *Emitted when a subscripted value doesn't support subscription (i.e. doesn't define \_\_getitem\_\_ method or \_\_class\_getitem\_\_ for a class).* **Problematic code:** ``` class Fruit: pass Fruit()[1] # [unsubscriptable-object] ``` **Correct code:** ``` class Fruit: def __init__(self): self.colors = ["red", "orange", "yellow"] def __getitem__(self, idx): return self.colors[idx] Fruit()[1] ``` Created by the typecheck \ checker. ### unsupported-assignment-operation / E1137 **Message emitted:** **%r does not support item assignment** **Description:** *Emitted when an object does not support item assignment (i.e. doesn't define \_\_setitem\_\_ method).* **Problematic code:** ``` def pick_fruits(fruits): for fruit in fruits: print(fruit) pick_fruits(["apple"])[0] = "orange" # [unsupported-assignment-operation] ``` **Correct code:** ``` def pick_fruits(fruits): for fruit in fruits: print(fruit) return [] pick_fruits(["apple"])[0] = "orange" ``` Created by the typecheck \ checker. ### unsupported-binary-operation / E1131 **Message emitted:** **%s** **Description:** *Emitted when a binary arithmetic operation between two operands is not supported.* **Problematic code:** ``` drink = "water" | None # [unsupported-binary-operation] result = [] | None # [unsupported-binary-operation] ``` **Correct code:** ``` masked = 0b111111 & 0b001100 result = 0xAEFF | 0x0B99 ``` **Configuration file:** ``` [main] py-version=3.9 ``` Created by the typecheck \ checker. ### unsupported-delete-operation / E1138 **Message emitted:** **%r does not support item deletion** **Description:** *Emitted when an object does not support item deletion (i.e. doesn't define \_\_delitem\_\_ method).* **Problematic code:** ``` FRUITS = ("apple", "orange", "berry") del FRUITS[0] # [unsupported-delete-operation] ``` **Correct code:** ``` FRUITS = ["apple", "orange", "berry"] del FRUITS[0] ``` Created by the typecheck \ checker. ### unsupported-membership-test / E1135 **Message emitted:** **Value '%s' doesn't support membership test** **Description:** *Emitted when an instance in membership test expression doesn't implement membership protocol (\_\_contains\_\_/\_\_iter\_\_/\_\_getitem\_\_).* **Problematic code:** ``` class Fruit: pass apple = "apple" in Fruit() # [unsupported-membership-test] ``` **Correct code:** ``` class Fruit: FRUITS = ["apple", "orange"] def __contains__(self, name): return name in self.FRUITS apple = "apple" in Fruit() ``` Created by the typecheck \ checker. ### used-before-assignment / E0601 **Message emitted:** **Using variable %r before assignment** **Description:** *Emitted when a local variable is accessed before its assignment took place. Assignments in try blocks are assumed not to have occurred when evaluating associated except/finally blocks. Assignments in except blocks are assumed not to have occurred when evaluating statements outside the block, except when the associated try block contains a return statement.* **Problematic code:** ``` print(hello) # [used-before-assignment] hello = "Hello World !" ``` **Correct code:** ``` hello = "Hello World !" print(hello) ``` Created by the variables \ checker. ### used-prior-global-declaration / E0118 **Message emitted:** **Name %r is used prior to global declaration** **Description:** *Emitted when a name is used prior a global declaration, which results in an error since Python 3.6.* **Problematic code:** ``` TOMATO = "black cherry" def update_tomato(): print(TOMATO) # [used-prior-global-declaration] global TOMATO TOMATO = "cherry tomato" ``` **Correct code:** ``` TOMATO = "black cherry" def update_tomato(): global TOMATO TOMATO = "moneymaker" ``` Created by the basic \ checker. ### yield-inside-async-function / E1700 **Message emitted:** **Yield inside async function** **Description:** *Used when an \`yield\` or \`yield from\` statement is found inside an async function.* **Problematic code:** ``` async def foo(): yield from [1, 2, 3] # [yield-inside-async-function] ``` **Correct code:** ``` async def foo(): def _inner_foo(): yield from [1, 2, 3] async def foo(): yield 42 ``` **Additional details:** The message can't be emitted when using Python \< 3.5. **Related links:** - • PEP 525 \ Created by the async \ checker. ### yield-outside-function / E0105 **Message emitted:** **Yield outside function** **Description:** *Used when a "yield" statement is found outside a function or method.* **Problematic code:** ``` for i in range(10): yield i # [yield-outside-function] ``` **Correct code:** ``` def one_to_ten(): for i in range(10): yield i ``` Created by the basic \ checker. All renamed messages in the error category: ### bad-context-manager / E0235 'bad-context-manager' has been renamed. The new message can be found at: ### bad-exception-context / E0703 'bad-exception-context' has been renamed. The new message can be found at: ### bad-option-value / E0012 'bad-option-value' has been renamed. The new message can be found at: ### useless-option-value / R0022 **Message emitted:** **Useless option value for '%s', %s** **Description:** *Used when a value for an option that is now deleted from pylint is encountered.* **Problematic code:** ``` """'bad-continuation' was removed from pylint in https://github.com/pylint-dev/pylint/pull/3571""" # pylint: disable=bad-continuation # [useless-option-value] ``` **Correct code:** ``` """'bad-continuation' was removed from pylint in https://github.com/pylint-dev/pylint/pull/3571""" ``` **Additional details:** You can disable this check if you don't want to cleanup your configuration of old messages. Created by the main \ checker. ### unknown-option-value / W0012 **Message emitted:** **Unknown option value for '%s', expected a valid pylint message and got '%s'** **Description:** *Used when an unknown value is encountered for an option.* **Problematic code:** ``` # pylint: disable=missnig-docstring # [unknown-option-value] ``` **Correct code:** ``` # pylint: disable=missing-docstring ``` Created by the main \ checker. ### maybe-no-member / E1103 'maybe-no-member' has been renamed. The new message can be found at: ### old-non-iterator-returned-2 / E0234 'old-non-iterator-returned-2' has been renamed. The new message can be found at: ### old-unbalanced-tuple-unpacking / E0632 'old-unbalanced-tuple-unpacking' has been renamed. The new message can be found at: ### unbalanced-tuple-unpacking / W0632 **Message emitted:** **Possible unbalanced tuple unpacking with sequence %s: left side has %d label%s, right side has %d value%s** **Description:** *Used when there is an unbalanced tuple unpacking in assignment* **Problematic code:** ``` fruits = ("orange", "apple", "strawberry", "peer") orange, apple, strawberry = fruits # [unbalanced-tuple-unpacking] ``` **Correct code:** ``` fruits = ("orange", "apple", "strawberry", "peer") orange, apple, *remaining_fruits = fruits ``` **Related links:** - • PEP 3132 - Extended Iterable Unpacking \ Created by the variables \ checker. ### unhashable-dict-key / E1140 'unhashable-dict-key' has been renamed. The new message can be found at: ### Warning All messages in the warning category: ### abstract-method / W0223 **Message emitted:** **Method %r is abstract in class %r but is not overridden in child class %r** **Description:** *Used when an abstract method (i.e. raise NotImplementedError) is not overridden in concrete class.* **Problematic code:** **abstract\_method.py**: ``` import abc class WildAnimal: @abc.abstractmethod def make_sound(self): pass class Panther(WildAnimal): # [abstract-method] pass ``` **function\_raising\_not\_implemented\_error.py**: ``` class Pet: def make_sound(self): raise NotImplementedError class Cat(Pet): # [abstract-method] pass ``` **Correct code:** **abstract\_method.py**: ``` import abc class WildAnimal: @abc.abstractmethod def make_sound(self): pass class Panther(WildAnimal): def make_sound(self): print("MEEEOW") ``` **function\_raising\_not\_implemented\_error.py**: ``` class Pet: def make_sound(self): raise NotImplementedError class Cat(Pet): def make_sound(self): print("Meeeow") ``` Created by the classes \ checker. ### anomalous-backslash-in-string / W1401 **Message emitted:** **Anomalous backslash in string: '%s'. String constant might be missing an r prefix.** **Description:** *Used when a backslash is in a literal string but not as an escape.* **Problematic code:** ``` string = "\z" # [syntax-error] ``` **Correct code:** **double\_escape.py**: ``` string = "\\z" ``` **existing\_escape\_sequence.py**: ``` string = "\t" ``` **r\_prefix.py**: ``` string = r"\z" ``` **Additional details:** **\\z** is same as **\\\\z** because there's no escape sequence for **z**. But it is not clear for the reader of the code. The only reason this is demonstrated to raise **syntax-error** is because pylint's CI now runs on Python 3.12, where this truly raises a **SyntaxError**. We hope to address this discrepancy in the documentation in the future. **Related links:** - • String and Bytes literals \ - • Long form stackoverflow explanation \ Created by the string \ checker. ### anomalous-unicode-escape-in-string / W1402 **Message emitted:** **Anomalous Unicode escape in byte string: '%s'. String constant might be missing an r or u prefix.** **Description:** *Used when an escape like u is encountered in a byte string where it has no effect.* **Problematic code:** ``` print(b"\u%b" % b"0394") # [syntax-error] ``` **Correct code:** ``` print(b"\\u%b" % b"0394") ``` Created by the string \ checker. ### arguments-differ / W0221 **Message emitted:** **%s %s %r method** **Description:** *Used when a method has a different number of arguments than in the implemented interface or in an overridden method. Extra arguments with default values are ignored.* **Problematic code:** ``` class Drink: def mix(self, fluid_one, fluid_two): return fluid_one + fluid_two class Cocktail(Drink): def mix(self, fluid_one, fluid_two, alcoholic_fluid): # [arguments-differ] return fluid_one + fluid_two + alcoholic_fluid ``` **Correct code:** **add\_option\_in\_base\_class.py**: ``` """ Here we assume that drink and cocktail are the same thing and should actually inherit from each over. We also assume that 'Drink' are 'Cocktail' without alcohol (we added the alcohol option in the base class). This permit to not have to modify the cocktails calls downstream but the case where an alcohol is mixed in a soft drink will need to be handled. """ class Drink: def mix(self, fluid_one, fluid_two, alcoholic_fluid=None): # if alcoholic_fluid is not None: # raise Exception(f"This soft drink has {alcoholic_fluid} in it !") return fluid_one + fluid_two class Cocktail(Drink): def mix(self, fluid_one, fluid_two, alcoholic_fluid): return fluid_one + fluid_two + alcoholic_fluid ``` **default\_value.py**: ``` """ Here we assume that drink and cocktail are the same thing and should actually inherit from each over. We also assume that any Cocktail can be treated like a Drink (if you add beer to it). This permit to not have to modify the calls downstream and causes the least amount of disturbance at the cost of making cocktails beer-based implicitly. """ class Drink: def mix(self, fluid_one, fluid_two): return fluid_one + fluid_two class Cocktail(Drink): def mix(self, fluid_one, fluid_two, alcoholic_fluid="Beer"): return fluid_one + fluid_two + alcoholic_fluid ``` **no\_inheritance.py**: ``` """ Here we assume that 'Drink' and 'Cocktail' are different things and should not be treated together like if they were the same thing. This will force some downstream changes and force the API user to make a conscious decision about the alcoholic content of its drink when using the API. For example, it's impossible to create a mojito with beer without explicitly wanting to, or to add an alcohol to a soft-drink. """ class Drink: def mix(self, fluid_one, fluid_two): return fluid_one + fluid_two class Cocktail: def mix(self, fluid_one, fluid_two, alcoholic_fluid): return fluid_one + fluid_two + alcoholic_fluid ``` **Additional details:** **argument-differ** denotes an issue with the Liskov Substitution Principle. This means that the code in question violates an important design principle which does not have one single solution. We recommend to search online for the best solution in your case. To give some examples of potential solutions: - • Add the argument to the parent class - • Remove the inheritance completely - • Add default arguments to the child class **Related links:** - • Liskov Substitution Principle \ Created by the classes \ checker. ### arguments-out-of-order / W1114 **Message emitted:** **Positional arguments appear to be out of order** **Description:** *Emitted when the caller's argument names fully match the parameter names in the function signature but do not have the same order.* **Problematic code:** ``` def function_3_args(first_argument, second_argument, third_argument): """Three arguments function""" return first_argument, second_argument, third_argument def args_out_of_order(): first_argument = 1 second_argument = 2 third_argument = 3 function_3_args( # [arguments-out-of-order] first_argument, third_argument, second_argument ) ``` **Correct code:** ``` def function_3_args(first_argument, second_argument, third_argument): """Three arguments function""" return first_argument, second_argument, third_argument def args_out_of_order(): first_argument = 1 second_argument = 2 third_argument = 3 function_3_args(first_argument, second_argument, third_argument) ``` Created by the typecheck \ checker. ### arguments-renamed / W0237 **Message emitted:** **%s %s %r method** **Description:** *Used when a method parameter has a different name than in the implemented interface or in an overridden method.* **Problematic code:** ``` class Fruit: def brew(self, ingredient_name: str): print(f"Brewing a {type(self)} with {ingredient_name}") class Apple(Fruit): ... class Orange(Fruit): def brew(self, flavor: str): # [arguments-renamed] print(f"Brewing an orange with {flavor}") for fruit, ingredient_name in [[Orange(), "thyme"], [Apple(), "cinnamon"]]: fruit.brew(ingredient_name=ingredient_name) ``` **Correct code:** ``` class Fruit: def brew(self, ingredient_name: str): print(f"Brewing a {type(self)} with {ingredient_name}") class Apple(Fruit): ... class Orange(Fruit): def brew(self, ingredient_name: str): print(f"Brewing an orange with {ingredient_name}") for fruit, ingredient_name in [[Orange(), "thyme"], [Apple(), "cinnamon"]]: fruit.brew(ingredient_name=ingredient_name) ``` Created by the classes \ checker. ### assert-on-string-literal / W0129 **Message emitted:** **Assert statement has a string literal as its first argument. The assert will %s fail.** **Description:** *Used when an assert statement has a string literal as its first argument, which will cause the assert to always pass.* **Problematic code:** ``` def test_division(): a = 9 / 3 assert "No ZeroDivisionError were raised" # [assert-on-string-literal] ``` **Correct code:** ``` def test_division(): a = 9 / 3 assert a == 3 ``` **Additional details:** Directly asserting a string literal will always pass. The solution is to test something that could fail, or not assert at all. For **unittest** assertions there is the similar redundant-unittest-assert / W1503 \<#redundant-unittest-assert\> message. **Related links:** - • Tests without assertion \ - • Testing that there is no error raised \ - • Parametrizing conditional raising \ Created by the basic \ checker. ### assert-on-tuple / W0199 **Message emitted:** **Assert called on a populated tuple. Did you mean 'assert x,y'?** **Description:** *A call of assert on a tuple will always evaluate to true if the tuple is not empty, and will always evaluate to false if it is.* **Problematic code:** ``` assert (1, None) # [assert-on-tuple] ``` **Correct code:** ``` x, y = (1, None) assert x assert y ``` **Additional details:** - **Directly asserting a non-empty tuple will always pass. The solution is to** test something that could fail, or not assert at all. For **unittest** assertions there is the similar redundant-unittest-assert / W1503 \<#redundant-unittest-assert\> message. Created by the basic \ checker. ### attribute-defined-outside-init / W0201 **Message emitted:** **Attribute %r defined outside \_\_init\_\_** **Description:** *Used when an instance attribute is defined outside the \_\_init\_\_ method.* **Problematic code:** ``` class Student: def register(self): self.is_registered = True # [attribute-defined-outside-init] ``` **Correct code:** ``` class Student: def __init__(self): self.is_registered = False def register(self): self.is_registered = True ``` Created by the classes \ checker. ### bad-builtin / W0141 **Message emitted:** **Used builtin function %s** **Description:** *Used when a disallowed builtin function is used (see the bad-function option). Usual disallowed functions are the ones like map, or filter , where Python offers now some cleaner alternative like list comprehension.* **Problematic code:** ``` numbers = list(map(lambda x: 2 * x, [1, 2, 3])) # [bad-builtin] print(numbers) ``` **Correct code:** ``` numbers = [2 * x for x in [1, 2, 3]] print(numbers) ``` **Configuration file:** ``` [MAIN] load-plugins = pylint.extensions.bad_builtin ``` **Note:** This message is emitted by the optional 'deprecated\_builtins' \<#pylint-extensions-bad-builtin\> checker, which requires the **pylint.extensions.bad\_builtin** plugin to be loaded. Created by the deprecated\_builtins \ checker. ### bad-chained-comparison / W3601 **Message emitted:** **Suspicious %s-part chained comparison using semantically incompatible operators (%s)** **Description:** *Used when there is a chained comparison where one expression is part of two comparisons that belong to different semantic groups ("\<" does not mean the same thing as "is", chaining them in "0 \< x is None" is probably a mistake).* **Problematic code:** **parrot.py**: ``` shop = { # animal: (specie, descriptions) "parrot": ("Norvegian blue", ("restin'", "remarkable", "beautiful plumage")), } if "parrot" in shop is "restin'": # [bad-chained-comparison] print("Hellooooo, Pooolllllyyy ! WAAAAKEEY, WAKKEEEY !") ``` **xor.py**: ``` def xor_check(*, left=None, right=None): if left is None != right is None: # [bad-chained-comparison] raise ValueError( "Either both left= and right= need to be provided or none should." ) ``` **Correct code:** **parrot.py**: ``` shop = { # animal: (specie, descriptions) "parrot": ("Norvegian blue", ("restin'", "remarkable", "beautiful plumage")), } if "parrot" in shop and "restin'" in shop["parrot"][1]: print("Hellooooo, Pooolllllyyy ! WAAAAKEEY, WAKKEEEY !") ``` **xor.py**: ``` def xor_check(*, left=None, right=None): if (left is None) != (right is None): raise ValueError( "Either both left= and right= need to be provided or none should." ) ``` **Related links:** - • Comparison Chaining \ Created by the bad-chained-comparison \ checker. ### bad-dunder-name / W3201 **Message emitted:** **Bad or misspelled dunder method name %s.** **Description:** *Used when a dunder method is misspelled or defined with a name not within the predefined list of dunder names.* **Problematic code:** ``` class Apples: def _init_(self): # [bad-dunder-name] pass def __hello__(self): # [bad-dunder-name] print("hello") ``` **Correct code:** ``` class Apples: def __init__(self): pass def hello(self): print("hello") ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.dunder ``` **Note:** This message is emitted by the optional 'dunder' \<#pylint-extensions-dunder\> checker, which requires the **pylint.extensions.dunder** plugin to be loaded. Created by the dunder \ checker. ### bad-format-string / W1302 **Message emitted:** **Invalid format string** **Description:** *Used when a PEP 3101 format string is invalid.* **Problematic code:** ``` print("{a[0] + a[1]}".format(a=[0, 1])) # [bad-format-string] ``` **Correct code:** ``` print("{a[0]} + {a[1]}".format(a=[0, 1])) ``` **Related links:** - • Format String Syntax \ - • PyFormat \ Created by the string \ checker. ### bad-format-string-key / W1300 **Message emitted:** **Format string dictionary key should be a string, not %s** **Description:** *Used when a format string that uses named conversion specifiers is used with a dictionary whose keys are not all strings.* **Problematic code:** ``` print("%(one)d" % {"one": 1, 2: 2}) # [bad-format-string-key] ``` **Correct code:** ``` print("%(one)d, %(two)d" % {"one": 1, "two": 2}) ``` **Additional details:** This check only works for old-style string formatting using the '%' operator. This check only works if the dictionary with the values to be formatted is defined inline. Passing a variable will not trigger the check as the other keys in this dictionary may be used in other contexts, while an inline defined dictionary is clearly only intended to hold the values that should be formatted. Created by the string \ checker. ### bad-indentation / W0311 **Message emitted:** **Bad indentation. Found %s %s, expected %s** **Description:** *Used when an unexpected number of indentation's tabulations or spaces has been found.* **Problematic code:** ``` if input(): print('yes') # [bad-indentation] ``` **Correct code:** ``` if input(): print("yes") ``` **Additional details:** The option **--indent-string** can be used to set the indentation unit for this check. Created by the format \ checker. ### bad-open-mode / W1501 **Message emitted:** **"%s" is not a valid mode for open.** **Description:** *Python supports: r, w, a\[, x\] modes with b, +, and U (only with r) options. See https://docs.python.org/3/library/functions.html#open* **Problematic code:** ``` def open_and_get_content(file_path): with open(file_path, "rwx") as file: # [bad-open-mode] return file.read() ``` **Correct code:** ``` def open_and_get_content(file_path): with open(file_path, "r") as file: return file.read() ``` Created by the stdlib \ checker. ### bad-staticmethod-argument / W0211 **Message emitted:** **Static method with %r as first argument** **Description:** *Used when a static method has "self" or a value specified in valid-classmethod-first-arg option or valid-metaclass-classmethod-first-arg option as first argument.* **Problematic code:** ``` class Wolf: @staticmethod def eat(self): # [bad-staticmethod-argument] pass ``` **Correct code:** ``` class Wolf: @staticmethod def eat(sheep): pass ``` Created by the classes \ checker. ### bad-thread-instantiation / W1506 **Message emitted:** **threading.Thread needs the target function** **Description:** *The warning is emitted when a threading.Thread class is instantiated without the target function being passed as a kwarg or as a second argument. By default, the first parameter is the group param, not the target param.* **Problematic code:** ``` import threading def thread_target(n): print(n**2) thread = threading.Thread(lambda: None) # [bad-thread-instantiation] thread.start() ``` **Correct code:** ``` import threading def thread_target(n): print(n**2) thread = threading.Thread(target=thread_target, args=(10,)) thread.start() ``` Created by the stdlib \ checker. ### bare-except / W0702 **Message emitted:** **No exception type(s) specified** **Description:** *A bare \`\`except:\`\` clause will catch \`\`SystemExit\`\` and \`\`KeyboardInterrupt\`\` exceptions, making it harder to interrupt a program with \`\`Control-C\`\`, and can disguise other problems. If you want to catch all exceptions that signal program errors, use \`\`except Exception:\`\` (bare except is equivalent to \`\`except BaseException:\`\`).* **Problematic code:** ``` try: import platform_specific_module except: # [bare-except] platform_specific_module = None ``` **Correct code:** ``` try: import platform_specific_module except ImportError: platform_specific_module = None ``` **Additional details:** A good rule of thumb is to limit use of bare ‘except’ clauses to two cases: - If the exception handler will be printing out or logging the traceback; at least the user will be aware that an error has occurred. - If the code needs to do some cleanup work, but then lets the exception propagate upwards with raise. **try...finally** can be a better way to handle this case. **Related links:** - • Programming recommendation in PEP8 \ - • PEP 760 – No More Bare Excepts (Rejected) \ - • Discussion about PEP 760 \ Created by the exceptions \ checker. ### binary-op-exception / W0711 **Message emitted:** **Exception to catch is the result of a binary "%s" operation** **Description:** *Used when the exception to catch is of the form "except A or B:". If intending to catch multiple, rewrite as "except (A, B):"* **Problematic code:** ``` try: 1 / 0 except ZeroDivisionError or ValueError: # [binary-op-exception] pass ``` **Correct code:** ``` try: 1 / 0 except (ZeroDivisionError, ValueError): pass ``` Created by the exceptions \ checker. ### boolean-datetime / W1502 **Message emitted:** **Using datetime.time in a boolean context.** **Description:** *Using datetime.time in a boolean context can hide subtle bugs when the time they represent matches midnight UTC. This behaviour was fixed in Python 3.5. See https://bugs.python.org/issue13936 for reference.* **Problematic code:** ``` import datetime if datetime.time(): # [boolean-datetime] print("It is time.") if datetime.datetime.now().time(): # [boolean-datetime] print("Now or never.") ``` **Correct code:** ``` import datetime time_now_utc = datetime.datetime.now(tz=datetime.UTC).time() if time_now_utc > datetime.time(6, 0): print("Daytime!") if time_now_utc < datetime.time(6, 0): print("Nighttime!") ``` **Configuration file:** ``` [main] py-version=3.4 ``` **Related links:** - • Python bug tracker \ Created by the stdlib \ checker. ### break-in-finally / W0137 **Message emitted:** **'break' discouraged inside 'finally' clause** **Description:** *Emitted when the \`break\` keyword is found inside a finally clause. This will raise a SyntaxWarning starting in Python 3.14.* **Problematic code:** ``` while True: try: pass finally: break # [break-in-finally] ``` **Correct code:** ``` while True: try: pass except ValueError: pass else: break ``` **Related links:** - • Python 3 docs 'finally' clause \ - • PEP 765 - Disallow return/break/continue that exit a finally block \ Created by the basic \ checker. ### broad-exception-caught / W0718 **Message emitted:** **Catching too general exception %s** **Description:** *If you use a naked \`\`except Exception:\`\` clause, you might end up catching exceptions other than the ones you expect to catch. This can hide bugs or make it harder to debug programs when unrelated errors are hidden.* **Problematic code:** ``` try: import platform_specific_module except Exception: # [broad-exception-caught] platform_specific_module = None ``` **Correct code:** ``` try: import platform_specific_module except ImportError: platform_specific_module = None ``` **Additional details:** For example, you're trying to import a library with required system dependencies and you catch everything instead of only import errors, you will miss the error message telling you, that your code could work if you had installed the system dependencies. **Related links:** - • Should I always specify an exception type in 'except' statements? \ Created by the exceptions \ checker. ### broad-exception-raised / W0719 **Message emitted:** **Raising too general exception: %s** **Description:** *Raising exceptions that are too generic force you to catch exceptions generically too. It will force you to use a naked \`\`except Exception:\`\` clause. You might then end up catching exceptions other than the ones you expect to catch. This can hide bugs or make it harder to debug programs when unrelated errors are hidden.* **Problematic code:** ``` def small_apple(apple, length): if len(apple) < length: raise Exception("Apple is too small!") # [broad-exception-raised] print(f"{apple} is proper size.") ``` **Correct code:** ``` def small_apple(apple, length): if len(apple) < length: raise ValueError("Apple is too small!") print(f"{apple} is proper size.") ``` **Related links:** - • Programming recommendation in PEP8 \ Created by the exceptions \ checker. ### cell-var-from-loop / W0640 **Message emitted:** **Cell variable %s defined in loop** **Description:** *A variable used in a closure is defined in a loop. This will result in all closures using the same value for the closed-over variable.* **Problematic code:** ``` def teacher_greeting(names): greetings = [] for name in names: def greet(): # do something print(f"Hello, {name}!") # [cell-var-from-loop] if name.isalpha(): greetings.append(greet) for greet in greetings: # the "name" variable is evaluated when the function is called here, # which is the last value it had in the loop - "Not-A-Name" greet() teacher_greeting(["Graham", "John", "Terry", "Eric", "Terry", "Michael"]) # "Hello, Michael!" # "Hello, Michael!" # "Hello, Michael!" # "Hello, Michael!" # "Hello, Michael!" ``` **Correct code:** **functools.partial.py**: ``` import functools def teacher_greeting(names): greetings = [] for name in names: if name.isalpha(): # "name" is evaluated when the partial is created here, so this # does not do lazy evaluation greetings.append(functools.partial(print, f"Hello, {name}!")) for greet in greetings: # `partial`s are called like functions, but you've already passed the # arguments to them greet() teacher_greeting(["Graham", "John", "Terry", "Eric", "Terry", "Michael"]) # "Hello, Graham!" # "Hello, John!" # "Hello, Eric!" # "Hello, Terry!" # "Hello, Michael!" ``` **new\_function.py**: ``` def teacher_greeting(names): def greet(name): # do something print(f"Hello, {name}!") for name in names: if name.isalpha(): # we're passing the value of "name" to the function here greet(name) teacher_greeting(["Graham", "John", "Terry", "Eric", "Terry", "Michael"]) # "Hello, Graham!" # "Hello, John!" # "Hello, Eric!" # "Hello, Terry!" # "Hello, Michael!" ``` **Related links:** - • Stackoverflow discussion \ Created by the variables \ checker. ### comparison-with-callable / W0143 **Message emitted:** **Comparing against a callable, did you omit the parenthesis?** **Description:** *This message is emitted when pylint detects that a comparison with a callable was made, which might suggest that some parenthesis were omitted, resulting in potential unwanted behaviour.* **Problematic code:** ``` def function_returning_a_fruit() -> str: return "orange" def is_an_orange(fruit: str = "apple"): # apple == return fruit == function_returning_a_fruit # [comparison-with-callable] ``` **Correct code:** ``` def function_returning_a_fruit() -> str: return "orange" def is_an_orange(fruit: str = "apple"): # apple == orange return fruit == function_returning_a_fruit() ``` Created by the basic \ checker. ### confusing-with-statement / W0124 **Message emitted:** **Following "as" with another context manager looks like a tuple.** **Description:** *Emitted when a \`with\` statement component returns multiple values and uses name binding with \`as\` only for a part of those values, as in with ctx() as a, b. This can be misleading, since it's not clear if the context manager returns a tuple or if the node without a name binding is another context manager.* **Problematic code:** ``` with open("file.txt", "w") as fh1, fh2: # [confusing-with-statement] pass ``` **Correct code:** ``` with open("file.txt", "w", encoding="utf8") as fh1: with open("file.txt", "w", encoding="utf8") as fh2: pass ``` Created by the basic \ checker. ### consider-ternary-expression / W0160 **Message emitted:** **Consider rewriting as a ternary expression** **Description:** *Multiple assign statements spread across if/else blocks can be rewritten with a single assignment and ternary expression* **Problematic code:** ``` x, y = input(), input() if x >= y: # [consider-ternary-expression] maximum = x else: maximum = y ``` **Correct code:** ``` x, y = input(), input() maximum = x if x >= y else y ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.consider_ternary_expression ``` **Note:** This message is emitted by the optional 'consider\_ternary\_expression' \<#pylint-extensions-consider-ternary-expression\> checker, which requires the **pylint.extensions.consider\_ternary\_expression** plugin to be loaded. Created by the consider\_ternary\_expression \ checker. ### contextmanager-generator-missing-cleanup / W0135 **Message emitted:** **The context used in function %r will not be exited.** **Description:** *Used when a contextmanager is used inside a generator function and the cleanup is not handled.* **Problematic code:** ``` import contextlib @contextlib.contextmanager def cm(): contextvar = "acquired context" print("cm enter") yield contextvar print("cm exit") def genfunc_with_cm(): with cm() as context: # [contextmanager-generator-missing-cleanup] yield context * 2 ``` **Correct code:** ``` import contextlib @contextlib.contextmanager def good_cm_except(): contextvar = "acquired context" print("good cm enter") try: yield contextvar except GeneratorExit: print("good cm exit") def genfunc_with_cm(): with good_cm_except() as context: yield context * 2 def genfunc_with_discard(): with good_cm_except(): yield "discarded" @contextlib.contextmanager def good_cm_yield_none(): print("good cm enter") yield print("good cm exit") def genfunc_with_none_yield(): with good_cm_yield_none() as var: print(var) yield "constant yield" @contextlib.contextmanager def good_cm_finally(): contextvar = "acquired context" print("good cm enter") try: yield contextvar finally: print("good cm exit") def good_cm_finally_genfunc(): with good_cm_finally() as context: yield context * 2 @contextlib.contextmanager def good_cm_no_cleanup(): contextvar = "acquired context" print("cm enter") yield contextvar def good_cm_no_cleanup_genfunc(): with good_cm_no_cleanup() as context: yield context * 2 ``` **Additional details:** Instantiating and using a contextmanager inside a generator function can result in unexpected behavior if there is an expectation that the context is only available for the generator function. In the case that the generator is not closed or destroyed then the context manager is held suspended as is. This message warns on the generator function instead of the contextmanager function because the ways to use a contextmanager are many. A contextmanager can be used as a decorator (which immediately has **\_\_enter\_\_**/**\_\_exit\_\_** applied) and the use of **as ...** or discard of the return value also implies whether the context needs cleanup or not. So for this message, warning the invoker of the contextmanager is important. The check can create false positives if **yield** is used inside an **if-else** block without custom cleanup. Use **pylint: disable** for these. ``` from contextlib import contextmanager @contextmanager def good_cm_no_cleanup(): contextvar = "acquired context" print("cm enter") if some_condition: yield contextvar else: yield contextvar def good_cm_no_cleanup_genfunc(): # pylint: disable-next=contextmanager-generator-missing-cleanup with good_cm_no_cleanup() as context: yield context * 2 ``` **Related links:** - • Rationale \ - • CPython Issue \ Created by the basic \ checker. ### continue-in-finally / W0136 **Message emitted:** **'continue' discouraged inside 'finally' clause** **Description:** *Emitted when the \`continue\` keyword is found inside a finally clause. This will raise a SyntaxWarning starting in Python 3.14.* **Problematic code:** ``` while True: try: pass finally: continue # [continue-in-finally] ``` **Correct code:** ``` while True: try: pass except ValueError: pass else: continue ``` **Related links:** - • Python 3 docs 'finally' clause \ - • PEP 765 - Disallow return/break/continue that exit a finally block \ Created by the basic \ checker. ### dangerous-default-value / W0102 **Message emitted:** **Dangerous default value %s as argument** **Description:** *Used when a mutable value as list or dictionary is detected in a default value for an argument.* **Problematic code:** ``` def whats_on_the_telly(penguin=[]): # [dangerous-default-value] penguin.append("property of the zoo") return penguin ``` **Correct code:** ``` def whats_on_the_telly(penguin=None): if penguin is None: penguin = [] penguin.append("property of the zoo") return penguin ``` **Additional details:** With a mutable default value, with each call the default value is modified, i.e.: ``` whats_on_the_telly() # ["property of the zoo"] whats_on_the_telly() # ["property of the zoo", "property of the zoo"] whats_on_the_telly() # ["property of the zoo", "property of the zoo", "property of the zoo"] ``` Created by the basic \ checker. ### deprecated-argument / W4903 **Message emitted:** **Using deprecated argument %s of method %s()** **Description:** *The argument is marked as deprecated and will be removed in the future.* **Problematic code:** ``` int(x=1) # [deprecated-argument] ``` **Correct code:** ``` int(1) ``` **Configuration file:** ``` ``` **Additional details:** The actual replacement needs to be studied on a case by case basis by reading the deprecation warning or the release notes. Created by the stdlib \ checker. ### deprecated-attribute / W4906 **Message emitted:** **Using deprecated attribute %r** **Description:** *The attribute is marked as deprecated and will be removed in the future.* **Problematic code:** ``` from configparser import ParsingError err = ParsingError("filename") source = err.filename # [deprecated-attribute] ``` **Correct code:** ``` from configparser import ParsingError err = ParsingError("filename") source = err.source ``` **Additional details:** The actual replacement needs to be studied on a case by case basis by reading the deprecation warning or the release notes. Created by the stdlib \ checker. ### deprecated-class / W4904 **Message emitted:** **Using deprecated class %s of module %s** **Description:** *The class is marked as deprecated and will be removed in the future.* **Problematic code:** ``` from collections import Iterable # [deprecated-class] ``` **Correct code:** ``` from collections.abc import Iterable ``` **Additional details:** The actual replacement needs to be studied on a case by case basis by reading the deprecation warning or the release notes. Created by the stdlib \ checker. ### deprecated-decorator / W4905 **Message emitted:** **Using deprecated decorator %s()** **Description:** *The decorator is marked as deprecated and will be removed in the future.* **Problematic code:** ``` import abc class Animal: @abc.abstractclassmethod # [deprecated-decorator] def breath(cls): pass ``` **Correct code:** ``` import abc class Animal: @abc.classmethod @abc.abstractmethod def breath(cls): pass ``` **Configuration file:** ``` [main] py-version = 3.3 ``` **Additional details:** The actual replacement needs to be studied on a case by case basis by reading the deprecation warning or the release notes. Created by the stdlib \ checker. ### deprecated-method / W4902 **Message emitted:** **Using deprecated method %s()** **Description:** *The method is marked as deprecated and will be removed in the future.* **Problematic code:** ``` import logging logging.warn("I'm coming, world !") # [deprecated-method] ``` **Correct code:** ``` import logging logging.warning("I'm coming, world !") ``` **Additional details:** The actual replacement needs to be studied on a case by case basis by reading the deprecation warning or the release notes. Created by the stdlib \ checker. ### deprecated-module / W4901 **Message emitted:** **Deprecated module %r** **Description:** *A module marked as deprecated is imported.* **Problematic code:** ``` import distutils # [deprecated-module] import whatever_you_want # [deprecated-module] ``` **Correct code:** ``` import setuptools import whatever_replacement_you_want ``` **Configuration file:** ``` [main] py-version=3.7 deprecated-modules=whatever_you_want ``` **Additional details:** The actual replacement needs to be studied on a case by case basis by reading the deprecation warning or the release notes. Created by the imports \ checker. ### deprecated-typing-alias / W6001 **Message emitted:** **'%s' is deprecated, use '%s' instead** **Description:** *Emitted when a deprecated typing alias is used.* **Problematic code:** ``` import typing item_to_number_of_item: typing.Dict[str, int] # [deprecated-typing-alias] ``` **Correct code:** ``` item_to_number_of_item: dict[str, int] ``` **Configuration file:** ``` [main] load-plugins = pylint.extensions.typing ``` **Note:** This message is emitted by the optional 'typing' \<#pylint-extensions-typing\> checker, which requires the **pylint.extensions.typing** plugin to be loaded. Created by the typing \ checker. ### differing-param-doc / W9017 **Message emitted:** **"%s" differing in parameter documentation** **Description:** *Please check parameter names in declarations.* **Problematic code:** ``` def add(x, y): # [differing-param-doc] """Add two numbers. :param int x: x value. :param int z: z value. """ return x + y ``` **Correct code:** ``` def add(x, y): """Add two numbers. :param int x: x value. :param int y: y value. """ return x + y ``` **Configuration file:** ``` [MAIN] load-plugins = pylint.extensions.docparams ``` **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### differing-type-doc / W9018 **Message emitted:** **"%s" differing in parameter type documentation** **Description:** *Please check parameter names in type declarations.* **Problematic code:** ``` def add(x: int, y: int): # [differing-type-doc] """Add two numbers. :param int xy: x value. :param str y: y value. """ return x + y ``` **Correct code:** ``` def add(x, y): """Add two numbers. :param int x: x value. :param int y: y value. """ return x + y ``` **Configuration file:** ``` [MAIN] load-plugins = pylint.extensions.docparams ``` **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### duplicate-except / W0705 **Message emitted:** **Catching previously caught exception type %s** **Description:** *Used when an except catches a type that was already caught by a previous handler.* **Problematic code:** ``` try: 1 / 0 except ZeroDivisionError: pass except ZeroDivisionError: # [duplicate-except] pass ``` **Correct code:** ``` try: 1 / 0 except ZeroDivisionError: pass ``` Created by the exceptions \ checker. ### duplicate-key / W0109 **Message emitted:** **Duplicate key %r in dictionary** **Description:** *Used when a dictionary expression binds the same key multiple times.* **Problematic code:** ``` test_score = {"Mathematics": 85, "Biology": 90, "Mathematics": 75} # [duplicate-key] ``` **Correct code:** ``` test_score = {"Mathematics": 85, "Biology": 90, "History": 75} ``` **Related links:** - • Python Dictionaries \ - • Mapping Types — dict \ Created by the basic \ checker. ### duplicate-string-formatting-argument / W1308 **Message emitted:** **Duplicate string formatting argument %r, consider passing as named argument** **Description:** *Used when we detect that a string formatting is repeating an argument instead of using named string arguments* **Problematic code:** ``` # pylint: disable=missing-docstring, consider-using-f-string SEE = "see 👀" SEA = "sea 🌊" # +1: [duplicate-string-formatting-argument,duplicate-string-formatting-argument] CONST = """ A sailor went to {}, {}, {} To {} what he could {}, {}, {} But all that he could {}, {}, {} Was the bottom of the deep blue {}, {}, {}! """.format( SEA, SEA, SEA, SEE, SEE, SEE, SEE, SEE, SEE, SEE, SEA, SEA, SEA, ) ``` **Correct code:** ``` # pylint: disable=missing-docstring, consider-using-f-string SEE = "see 👀" SEA = "sea 🌊" CONST = """ A sailor went to {sea}, {sea}, {sea} To {see} what he could {see}, {see}, {see} But all that he could {see}, {see}, {see} Was the bottom of the deep blue {sea}, {sea}, {sea}! """.format( sea=SEA, see=SEE ) ``` Created by the string \ checker. ### duplicate-value / W0130 **Message emitted:** **Duplicate value %r in set** **Description:** *This message is emitted when a set contains the same value two or more times.* **Problematic code:** ``` incorrect_set = {"value1", 23, 5, "value1"} # [duplicate-value] ``` **Correct code:** ``` correct_set = {"value1", 23, 5} ``` Created by the basic \ checker. ### eq-without-hash / W1641 **Message emitted:** **Implementing \_\_eq\_\_ without also implementing \_\_hash\_\_** **Description:** *Used when a class implements \_\_eq\_\_ but not \_\_hash\_\_. Objects get None as their default \_\_hash\_\_ implementation if they also implement \_\_eq\_\_.* **Problematic code:** ``` class Fruit: # [eq-without-hash] def __init__(self) -> None: self.name = "apple" def __eq__(self, other: object) -> bool: return isinstance(other, Fruit) and other.name == self.name ``` **Correct code:** ``` class Fruit: def __init__(self) -> None: self.name = "apple" def __eq__(self, other: object) -> bool: return isinstance(other, Fruit) and other.name == self.name def __hash__(self) -> int: return hash(self.name) ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.eq_without_hash, ``` **Note:** This message is emitted by the optional 'eq-without-hash' \<#pylint-extensions-eq-without-hash\> checker, which requires the **pylint.extensions.eq\_without\_hash** plugin to be loaded. Created by the eq-without-hash \ checker. ### eval-used / W0123 **Message emitted:** **Use of eval** **Description:** *Used when you use the "eval" function, to discourage its usage. Consider using \`ast.literal\_eval\` for safely evaluating strings containing Python expressions from untrusted sources.* **Problematic code:** ``` eval("[1, 2, 3]") # [eval-used] ``` **Correct code:** ``` from ast import literal_eval literal_eval("[1, 2, 3]") ``` Created by the basic \ checker. ### exec-used / W0122 **Message emitted:** **Use of exec** **Description:** *Raised when the 'exec' statement is used. It's dangerous to use this function for a user input, and it's also slower than actual code in general. This doesn't mean you should never use it, but you should consider alternatives first and restrict the functions available.* **Problematic code:** ``` username = "Ada" code_to_execute = f"""input('Enter code to be executed please, {username}: ')""" program = exec(code_to_execute) # [exec-used] exec(program) # [exec-used] ``` **Correct code:** ``` def get_user_code(name): return input(f"Enter code to be executed please, {name}: ") username = "Ada" # If the globals dictionary does not contain a value for the key __builtins__, # all builtins are allowed. You need to be explicit about it being disallowed. allowed_globals = {"__builtins__": {}} allowed_locals = {} # pylint: disable-next=exec-used exec(get_user_code(username), allowed_globals, allowed_locals) ``` **Additional details:** The available methods and variables used in **exec()** may introduce a security hole. You can restrict the use of these variables and methods by passing optional globals and locals parameters (dictionaries) to the **exec()** method. However, use of **exec()** is still insecure if you allow some functions like **\_\_import\_\_** or **open**. For example, consider the following call that writes a file to the user's system and then execute code unrestrained by the **allowed\_globals**, or **allowed\_locals** parameters: ``` import textwrap def forbid_print(*args): raise ValueError("This is raised when a print is used") allowed_globals = { "__builtins__": { "__import__": __builtins__.__import__, "open": __builtins__.open, "print": forbid_print, } } exec( textwrap.dedent( """ import textwrap with open("nefarious.py", "w") as f: f.write(textwrap.dedent(''' def connive(): print("Here's some code as nefarious as imaginable") ''')) import nefarious nefarious.connive() # This will NOT raise a ValueError """ ), allowed_globals, ) ``` The import is used only for readability of the example in this case but it could import a dangerous functions: - • **subprocess.run('echo "print(\\"Hello, World!\\")" \> nefarious.py'** - • **pathlib.Path("nefarious.py").write\_file("print(\\"Hello, World!\\")")** - • **os.system('echo "print(\\"Hello, World!\\")" \> nefarious.py')** - • **logging.basicConfig(filename='nefarious.py'); logging.error('print("Hello, World!")')** - • etc. **Related links:** - • Be careful with exec and eval in Python \ - • Python documentation \ Created by the basic \ checker. ### expression-not-assigned / W0106 **Message emitted:** **Expression "%s" is assigned to nothing** **Description:** *Used when an expression that is not a function call is assigned to nothing. Probably something else was intended.* **Problematic code:** ``` str(42) == "42" # [expression-not-assigned] ``` **Correct code:** ``` are_equal: bool = str(42) == "42" ``` Created by the basic \ checker. ### f-string-without-interpolation / W1309 **Message emitted:** **Using an f-string that does not have any interpolated variables** **Description:** *Used when we detect an f-string that does not use any interpolation variables, in which case it can be either a normal string or a bug in the code.* **Problematic code:** ``` x = 1 y = 2 print(f"x + y = x + y") # [f-string-without-interpolation] ``` **Correct code:** ``` x = 1 y = 2 print(f"{x} + {y} = {x + y}") ``` Created by the string \ checker. ### fixme / W0511 **Message emitted:** **%s** **Description:** *Used when a warning note as FIXME or XXX is detected.* **Problematic code:** ``` # TODO: We should fix this at some point # [fixme] ``` **Correct code:** **bug\_tracker.py**: ``` # The issue was added to the bug tracker: no longer need the comment ``` **fixed.py**: ``` # The issue was fixed: no longer need the comment ``` **no\_fix.py**: ``` # We no longer want to fix this: no longer need the comment ``` **Additional details:** You can use regular expressions and the **notes-rgx** option to create some constraints for this message. See the following issue \ for some examples. Created by the miscellaneous \ checker. ### forgotten-debug-statement / W1515 **Message emitted:** **Leaving functions creating breakpoints in production code is not recommended** **Description:** *Calls to breakpoint(), sys.breakpointhook() and pdb.set\_trace() should be removed from code that is not actively being debugged.* **Problematic code:** ``` import pdb def find_the_treasure(clues): for clue in clues: pdb.set_trace() # [forgotten-debug-statement] if "treasure" in clue: return True return False treasure_hunt = [ "Dead Man's Chest", "X marks the spot", "The treasure is buried near the palm tree", ] find_the_treasure(treasure_hunt) ``` **Correct code:** ``` def find_the_treasure(clues): for clue in clues: if "treasure" in clue: return True return False treasure_hunt = [ "Dead Man's Chest", "X marks the spot", "The treasure is buried near the palm tree", ] find_the_treasure(treasure_hunt) ``` Created by the stdlib \ checker. ### format-combined-specification / W1305 **Message emitted:** **Format string contains both automatic field numbering and manual field specification** **Description:** *Used when a PEP 3101 format string contains both automatic field numbering (e.g. '{}') and manual field specification (e.g. '{0}').* **Problematic code:** ``` print("{} {1}".format("hello", "world")) # [format-combined-specification] ``` **Correct code:** **index\_formatting.py**: ``` print("{0} {1}".format("hello", "world")) ``` **order\_formatting.py**: ``` print("{} {}".format("hello", "world")) ``` Created by the string \ checker. ### format-string-without-interpolation / W1310 **Message emitted:** **Using formatting for a string that does not have any interpolated variables** **Description:** *Used when we detect a string that does not have any interpolation variables, in which case it can be either a normal string without formatting or a bug in the code.* **Problematic code:** ``` print("number".format(1)) # [format-string-without-interpolation] ``` **Correct code:** ``` print("number: {}".format(1)) ``` Created by the string \ checker. ### global-at-module-level / W0604 **Message emitted:** **Using the global statement at the module level** **Description:** *Used when you use the "global" statement at the module level since it has no effect.* **Problematic code:** ``` price = 25 global price # [global-at-module-level] ``` **Correct code:** ``` price = 25 ``` **Related links:** - • Official Python FAQ - global and local \ - • PEP 3104 - Access to Names in Outer Scopes \ - • Python global statement \ Created by the variables \ checker. ### global-statement / W0603 **Message emitted:** **Using the global statement** **Description:** *Used when you use the "global" statement to update a global variable. Pylint discourages its usage. That doesn't mean you cannot use it!* **Problematic code:** ``` var = 1 def foo(): global var # [global-statement] var = 10 print(var) foo() print(var) ``` **Correct code:** ``` var = 1 def foo(): print(var) return 10 var = foo() print(var) ``` Created by the variables \ checker. ### global-variable-not-assigned / W0602 **Message emitted:** **Using global for %r but no assignment is done** **Description:** *When a variable defined in the global scope is modified in an inner scope, the 'global' keyword is required in the inner scope only if there is an assignment operation done in the inner scope.* **Problematic code:** ``` TOMATO = "black cherry" def update_tomato(): global TOMATO # [global-variable-not-assigned] print(TOMATO) ``` **Correct code:** ``` TOMATO = "black cherry" def update_tomato(): global TOMATO TOMATO = "moneymaker" ``` Created by the variables \ checker. ### global-variable-undefined / W0601 **Message emitted:** **Global variable %r undefined at the module level** **Description:** *Used when a variable is defined through the "global" statement but the variable is not defined in the module scope.* **Problematic code:** ``` def update_tomato(): global TOMATO # [global-variable-undefined] TOMATO = "moneymaker" ``` **Correct code:** ``` TOMATO = "black cherry" def update_tomato(): global TOMATO TOMATO = "moneymaker" ``` Created by the variables \ checker. ### implicit-flag-alias / W0213 **Message emitted:** **Flag member %(overlap)s shares bit positions with %(sources)s** **Description:** *Used when multiple integer values declared within an enum.IntFlag class share a common bit position.* **Problematic code:** ``` from enum import IntFlag class FilePermissions(IntFlag): READ = 1 WRITE = 2 EXECUTE = 3 # [implicit-flag-alias] ``` **Correct code:** ``` from enum import IntFlag class FilePermissions(IntFlag): READ = 1 WRITE = 2 EXECUTE = 4 ``` Created by the classes \ checker. ### implicit-str-concat / W1404 **Message emitted:** **Implicit string concatenation found in %s** **Description:** *String literals are implicitly concatenated in a literal iterable definition : maybe a comma is missing ?* **Problematic code:** **list.py**: ``` x = ["a" "b"] # [implicit-str-concat] ``` **open.py**: ``` with open("hello.txt" "r") as f: # [implicit-str-concat] print(f.read()) ``` **Correct code:** **list.py**: ``` x = ["a", "b"] ``` **open.py**: ``` with open("hello.txt", "r") as f: print(f.read()) ``` **Additional details:** By default, detection of implicit string concatenation of line jumps is disabled. Hence the following code will not trigger this rule: ``` SEQ = ('a', 'b' 'c') ``` In order to detect this case, you must enable *check-str-concat-over-line-jumps*: ``` [STRING_CONSTANT] check-str-concat-over-line-jumps = true ``` However, the drawback of this setting is that it will trigger false positive for string parameters passed on multiple lines in function calls: ``` warnings.warn( "rotate() is deprecated and will be removed in a future release. " "Use the rotation() context manager instead.", DeprecationWarning, stacklevel=3, ) ``` No message will be emitted, though, if you clarify the wanted concatenation with parentheses: ``` warnings.warn( ( "rotate() is deprecated and will be removed in a future release. " "Use the rotation() context manager instead." ), DeprecationWarning, stacklevel=3, ) ``` Created by the string \ checker. ### import-self / W0406 **Message emitted:** **Module import itself** **Description:** *Used when a module is importing itself.* **Additional details:** Say you have a file called **my\_file.py**. **import-self** would be raised on the following code: ``` from my_file import a_function # [import-self] def a_function(): pass ``` The solution would be to remove the import: ``` def a_function(): pass ``` Created by the imports \ checker. ### inconsistent-quotes / W1405 **Message emitted:** **Quote delimiter %s is inconsistent with the rest of the file** **Description:** *Quote delimiters are not used consistently throughout a module (with allowances made for avoiding unnecessary escaping).* **Problematic code:** ``` import datetime print('Current year: ', datetime.date.today().strftime("%Y")) # [inconsistent-quotes] ``` **Correct code:** ``` import datetime print("Current year: ", datetime.date.today().strftime("%Y")) ``` **Configuration file:** ``` [main] check-quote-consistency=yes ``` Created by the string \ checker. ### invalid-envvar-default / W1508 **Message emitted:** **%s default type is %s. Expected str or None.** **Description:** *Env manipulation functions return None or str values. Supplying anything different as a default may cause bugs. See https://docs.python.org/3/library/os.html#os.getenv.* **Problematic code:** ``` import os env = os.getenv("SECRET_KEY", 1) # [invalid-envvar-default] ``` **Correct code:** ``` import os env = os.getenv("SECRET_KEY", "1") ``` Created by the stdlib \ checker. ### invalid-format-index / W1307 **Message emitted:** **Using invalid lookup key %r in format specifier %r** **Description:** *Used when a PEP 3101 format string uses a lookup specifier ({a\[1\]}), but the argument passed for formatting doesn't contain or doesn't have that key as an attribute.* **Problematic code:** ``` not_enough_fruits = ["apple"] print('The second fruit is a {fruits[1]}'.format(fruits=not_enough_fruits)) # [invalid-format-index] ``` **Correct code:** ``` enough_fruits = ["apple", "banana"] print("The second fruit is a {fruits[1]}".format(fruits=enough_fruits)) ``` Created by the string \ checker. ### invalid-overridden-method / W0236 **Message emitted:** **Method %r was expected to be %r, found it instead as %r** **Description:** *Used when we detect that a method was overridden in a way that does not match its base class which could result in potential bugs at runtime.* **Problematic code:** ``` class Fruit: async def bore(self, insect): insect.eat(self) class Apple(Fruit): def bore(self, insect): # [invalid-overridden-method] insect.eat(self) ``` **Correct code:** ``` class Fruit: async def bore(self, insect): insect.eat(self) class Apple(Fruit): async def bore(self, insect): insect.eat(self) ``` Created by the classes \ checker. ### isinstance-second-argument-not-valid-type / W1116 **Message emitted:** **Second argument of isinstance is not a type** **Description:** *Emitted when the second argument of an isinstance call is not a type.* **Problematic code:** ``` isinstance("apples and oranges", hex) # [isinstance-second-argument-not-valid-type] ``` **Correct code:** ``` isinstance("apples and oranges", str) ``` Created by the typecheck \ checker. ### keyword-arg-before-vararg / W1113 **Message emitted:** **Keyword argument before variable positional arguments list in the definition of %s function** **Description:** *When defining a keyword argument before variable positional arguments, one can end up in having multiple values passed for the aforementioned parameter in case the method is called with keyword arguments.* **Problematic code:** ``` def func(x=None, *args): # [keyword-arg-before-vararg] return [x, *args] ``` **Correct code:** ``` def func(*args, x=None): return [*args, x] ``` Created by the typecheck \ checker. ### kwarg-superseded-by-positional-arg / W1117 **Message emitted:** **%r will be included in %r since a positional-only parameter with this name already exists** **Description:** *Emitted when a function is called with a keyword argument that has the same name as a positional-only parameter and the function contains a keyword variadic parameter dict.* **Problematic code:** ``` def print_name(name="Sarah", /, **kwds): print(name) print_name(name="Jacob") # [kwarg-superseded-by-positional-arg] # Will print "Sarah" ``` **Correct code:** ``` def print_name(name="Sarah", /, **kwds): print(name) print_name("Jacob") # Will print "Jacob" ``` Created by the typecheck \ checker. ### logging-format-interpolation / W1202 **Message emitted:** **Use %s formatting in logging functions** **Description:** *Used when a logging statement has a call form of "logging.\(format\_string.format(format\_args...))". Use another type of string formatting instead. You can use % formatting but leave interpolation to the logging function by passing the parameters as arguments. If logging-fstring-interpolation is disabled then you can use fstring formatting. If logging-not-lazy is disabled then you can use % formatting as normal.* **Problematic code:** ``` import logging import sys # +1: [logging-format-interpolation] logging.error("Python version: {}".format(sys.version)) ``` **Correct code:** ``` import logging import sys logging.error("Python version: %s", sys.version) ``` **Additional details:** Another reasonable option is to use f-string. If you want to do that, you need to enable **logging-format-interpolation** and disable **logging-fstring-interpolation**. **Related links:** - • logging variable data \ - • Rationale for the message on stackoverflow \ Created by the logging \ checker. ### logging-fstring-interpolation / W1203 **Message emitted:** **Use %s formatting in logging functions** **Description:** *Used when a logging statement has a call form of "logging.\(f"...")".Use another type of string formatting instead. You can use % formatting but leave interpolation to the logging function by passing the parameters as arguments. If logging-format-interpolation is disabled then you can use str.format. If logging-not-lazy is disabled then you can use % formatting as normal.* **Problematic code:** ``` import logging import sys logging.error(f"Python version: {sys.version}") # [logging-fstring-interpolation] ``` **Correct code:** ``` import logging import sys logging.error("Python version: %s", sys.version) ``` **Additional details:** This message permits to allow f-string in logging and still be warned of **logging-format-interpolation**. **Related links:** - • logging variable data \ - • Rationale \ Created by the logging \ checker. ### logging-not-lazy / W1201 **Message emitted:** **Use %s formatting in logging functions** **Description:** *Used when a logging statement has a call form of "logging.\(format\_string % (format\_args...))". Use another type of string formatting instead. You can use % formatting but leave interpolation to the logging function by passing the parameters as arguments. If logging-fstring-interpolation is disabled then you can use fstring formatting. If logging-format-interpolation is disabled then you can use str.format.* **Problematic code:** ``` import logging try: function() except Exception as e: logging.error("Error occurred: %s" % e) # [logging-not-lazy] raise ``` **Correct code:** ``` import logging try: function() except Exception as e: logging.error("Error occurred: %s", e) raise ``` **Additional details:** Another reasonable option is to use f-strings. If you want to do that, you need to enable **logging-not-lazy** and disable **logging-fstring-interpolation**. **Related links:** - • Logging variable data \ - • Rationale for the message on stackoverflow \ Created by the logging \ checker. ### lost-exception / W0150 **Message emitted:** **%s statement in finally block may swallow exception** **Description:** *Used when a break or a return statement is found inside the finally clause of a try...finally block: the exceptions raised in the try clause will be silently swallowed instead of being re-raised.* **Problematic code:** ``` class FasterThanTheSpeedOfLightError(ZeroDivisionError): def __init__(self): super().__init__("You can't go faster than the speed of light !") def calculate_speed(distance: float, time: float) -> float: try: return distance / time except ZeroDivisionError as e: raise FasterThanTheSpeedOfLightError() from e finally: return 299792458 # [lost-exception] ``` **Correct code:** ``` class FasterThanTheSpeedOfLightError(ZeroDivisionError): def __init__(self): super().__init__("You can't go faster than the speed of light !") def calculate_speed(distance: float, time: float) -> float: try: return distance / time except ZeroDivisionError as e: raise FasterThanTheSpeedOfLightError() from e ``` Created by the basic \ checker. ### method-cache-max-size-none / W1518 **Message emitted:** **'lru\_cache(maxsize=None)' or 'cache' will keep all method args alive indefinitely, including 'self'** **Description:** *By decorating a method with lru\_cache or cache the 'self' argument will be linked to the function and therefore never garbage collected. Unless your instance will never need to be garbage collected (singleton) it is recommended to refactor code to avoid this pattern or add a maxsize to the cache. The default value for maxsize is 128.* **Problematic code:** ``` import functools class Fibonnaci: def __init__(self): self.result = [] @functools.lru_cache(maxsize=None) # [method-cache-max-size-none] def fibonacci(self, n): if n in {0, 1}: self.result.append(n) self.result.append(self.fibonacci(n - 1) + self.fibonacci(n - 2)) ``` **Correct code:** ``` import functools @functools.cache def cached_fibonacci(n): if n in {0, 1}: return n return cached_fibonacci(n - 1) + cached_fibonacci(n - 2) class Fibonnaci: def __init__(self): self.result = [] def fibonacci(self, n): self.result.append(cached_fibonacci(n)) ``` Created by the stdlib \ checker. ### misplaced-future / W0410 **Message emitted:** **\_\_future\_\_ import is not the first non docstring statement** **Description:** *Python 2.5 and greater require \_\_future\_\_ import to be the first non docstring statement in the module.* **Problematic code:** ``` import sys from __future__ import print_function # [misplaced-future] ``` **Correct code:** ``` from __future__ import print_function import sys ``` **Additional details:** A bare raise statement will re-raise the last active exception in the current scope. If the **raise** statement is not in an **except** or **finally** block, a RuntimeError will be raised instead. Created by the imports \ checker. ### missing-any-param-doc / W9021 **Message emitted:** **Missing any documentation in "%s"** **Description:** *Please add parameter and/or type documentation.* **Problematic code:** ``` def puppies(head, tail): # [missing-any-param-doc] """Print puppy's details.""" print(head, tail) ``` **Correct code:** ``` def puppies(head: str, tail: str): """Print puppy's details. :param head: description of the head of the dog :param tail: description of the tail of the dog """ print(head, tail) ``` **Configuration file:** ``` [main] load-plugins = pylint.extensions.docparams accept-no-param-doc = false ``` **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### missing-format-argument-key / W1303 **Message emitted:** **Missing keyword argument %r for format string** **Description:** *Used when a PEP 3101 format string that uses named fields doesn't receive one or more required keywords.* **Problematic code:** ``` print("My name is {first} {last}".format(first="John")) # [missing-format-argument-key] ``` **Correct code:** ``` print("My name is {first} {last}".format(first="John", last="Wick")) ``` **Related links:** - • PEP 3101 \ - • Custom String Formatting \ Created by the string \ checker. ### missing-format-attribute / W1306 **Message emitted:** **Missing format attribute %r in format specifier %r** **Description:** *Used when a PEP 3101 format string uses an attribute specifier ({0.length}), but the argument passed for formatting doesn't have that attribute.* **Problematic code:** ``` print("{0.real}".format("1")) # [missing-format-attribute] ``` **Correct code:** ``` print("{0.real}".format(1)) ``` Created by the string \ checker. ### missing-param-doc / W9015 **Message emitted:** **"%s" missing in parameter documentation** **Description:** *Please add parameter declarations for all parameters.* **Problematic code:** ``` def integer_sum(a: int, b): # [missing-param-doc] """Returns sum of two integers :param a: first integer """ return a + b ``` **Correct code:** ``` def integer_sum(a: int, b: int): """Returns sum of two integers :param a: first integer :param b: second integer """ return a + b ``` **Configuration file:** ``` [MAIN] load-plugins = pylint.extensions.docparams ``` **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### missing-parentheses-for-call-in-test / W0126 **Message emitted:** **Using a conditional statement with potentially wrong function or method call due to missing parentheses** **Description:** *Emitted when a conditional statement (If or ternary if) seems to wrongly call a function due to missing parentheses* **Problematic code:** ``` import random def is_it_a_good_day(): return random.choice([True, False]) if is_it_a_good_day: # [missing-parentheses-for-call-in-test] print("Today is a good day!") ``` **Correct code:** ``` import random def is_it_a_good_day(): return random.choice([True, False]) if is_it_a_good_day(): print("Today is a good day!") ``` Created by the basic \ checker. ### missing-raises-doc / W9006 **Message emitted:** **"%s" not documented as being raised** **Description:** *Please document exceptions for all raised exception types.* **Problematic code:** ``` def integer_sum(a: int, b: int): # [missing-raises-doc] """Returns sum of two integers :param a: first integer :param b: second integer """ if not (isinstance(a, int) and isinstance(b, int)): raise ValueError("Function supports only integer parameters.") return a + b ``` **Correct code:** ``` def integer_sum(a: int, b: int): """Returns sum of two integers :param a: first integer :param b: second integer :raises ValueError: One of the parameters is not an integer. """ if not (isinstance(a, int) and isinstance(b, int)): raise ValueError("Function supports only integer parameters.") return a + b ``` **Configuration file:** ``` [MAIN] load-plugins = pylint.extensions.docparams [BASIC] accept-no-raise-doc = no ``` **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### missing-return-doc / W9011 **Message emitted:** **Missing return documentation** **Description:** *Please add documentation about what this method returns.* **Problematic code:** ``` def integer_sum(a: int, b: int): # [missing-return-doc] """Returns sum of two integers :param a: first integer :param b: second integer """ return a + b ``` **Correct code:** ``` def integer_sum(a: int, b: int) -> int: """Returns sum of two integers :param a: first integer :param b: second integer :return: sum of parameters a and b """ return a + b ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.docparams [Parameter_documentation] accept-no-return-doc=no ``` **Additional details:** This message is raised only when parameter **accept-no-return-doc** is set to **no**. **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### missing-return-type-doc / W9012 **Message emitted:** **Missing return type documentation** **Description:** *Please document the type returned by this method.* **Problematic code:** ``` def integer_sum(a: int, b: int): # [missing-return-type-doc] """Returns sum of two integers :param a: first integer :param b: second integer :return: sum of parameters a and b """ return a + b ``` **Correct code:** ``` def integer_sum(a: int, b: int) -> int: """Returns sum of two integers :param a: first integer :param b: second integer :return: sum of parameters a and b """ return a + b ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.docparams [Parameter_documentation] accept-no-return-doc=no ``` **Additional details:** This message is raised only when parameter **accept-no-return-doc** is set to **no**. **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### missing-timeout / W3101 **Message emitted:** **Missing timeout argument for method '%s' can cause your program to hang indefinitely** **Description:** *Used when a method needs a 'timeout' parameter in order to avoid waiting for a long time. If no timeout is specified explicitly the default value is used. For example for 'requests' the program will never time out (i.e. hang indefinitely).* **Problematic code:** ``` import requests requests.post("http://localhost") # [missing-timeout] ``` **Correct code:** ``` import requests requests.post("http://localhost", timeout=10) ``` **Additional details:** You can add new methods that should have a defined **\`timeout** argument as qualified names in the **timeout-methods** option, for example: - • **requests.api.get** - • **requests.api.head** - • **requests.api.options** - • **requests.api.patch** - • **requests.api.post** - • **requests.api.put** - • **requests.api.request** Created by the method\_args \ checker. ### missing-type-doc / W9016 **Message emitted:** **"%s" missing in parameter type documentation** **Description:** *Please add parameter type declarations for all parameters.* **Problematic code:** ``` def integer_sum(a: int, b): # [missing-type-doc] """Returns sum of two integers :param a: first integer :param b: second integer """ return a + b ``` **Correct code:** ``` def integer_sum(a: int, b: int): """Returns sum of two integers :param a: first integer :param b: second integer """ return a + b ``` **Configuration file:** ``` [MAIN] load-plugins = pylint.extensions.docparams ``` **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### missing-yield-doc / W9013 **Message emitted:** **Missing yield documentation** **Description:** *Please add documentation about what this generator yields.* **Problematic code:** ``` def even_number_under(n: int): # [missing-yield-doc] """Prints even numbers smaller than n. Args: n: Upper limit of even numbers. """ for i in range(n): if i % 2 == 1: continue yield i ``` **Correct code:** ``` from typing import Iterator def even_number_under(n: int) -> Iterator[int]: """Prints even numbers smaller than n. Args: n: Upper limit of even numbers. Yields: even numbers """ for i in range(n): if i % 2 == 1: continue yield i ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.docparams [Parameter_documentation] accept-no-yields-doc=no ``` **Additional details:** This message is raised only when parameter **accept-no-yields-doc** is set to **no**. **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### missing-yield-type-doc / W9014 **Message emitted:** **Missing yield type documentation** **Description:** *Please document the type yielded by this method.* **Problematic code:** ``` def even_number_under(n: int): # [missing-yield-type-doc] """Prints even numbers smaller than n. Args: n: Upper limit of even numbers. Yields: even numbers """ for i in range(n): if i % 2 == 1: continue yield i ``` **Correct code:** ``` from typing import Iterator def even_number_under(n: int) -> Iterator[int]: """Prints even numbers smaller than n. Args: n: Upper limit of even numbers. Yields: even numbers """ for i in range(n): if i % 2 == 1: continue yield i ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.docparams [Parameter_documentation] accept-no-yields-doc=no ``` **Additional details:** This message is raised only when parameter **accept-no-yields-doc** is set to **no**. **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### modified-iterating-list / W4701 **Message emitted:** **Iterated list '%s' is being modified inside for loop body, consider iterating through a copy of it instead.** **Description:** *Emitted when items are added or removed to a list being iterated through. Doing so can result in unexpected behaviour, that is why it is preferred to use a copy of the list.* **Problematic code:** ``` fruits = ["apple", "orange", "mango"] for fruit in fruits: fruits.append("pineapple") # [modified-iterating-list] ``` **Correct code:** ``` fruits = ["apple", "orange", "mango"] for fruit in fruits.copy(): fruits.append("pineapple") ``` Created by the modified\_iteration \ checker. ### multiple-constructor-doc / W9005 **Message emitted:** **"%s" has constructor parameters documented in class and \_\_init\_\_** **Description:** *Please remove parameter declarations in the class or constructor.* **Problematic code:** ``` class Point: # [multiple-constructor-doc] """Represents a point in the xy-coordinate plane. :param x: coordinate :param y: coordinate """ def __init__(self, x, y): """Represents a point in the xy-coordinate plane. :param x: coordinate :param y: coordinate """ self.x = x self.y = y ``` **Correct code:** ``` class Point: def __init__(self, x, y): """Represents a point in the xy-coordinate plane. :param x: x coordinate :param y: y coordinate """ self.x = x self.y = y ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.docparams [Parameter_documentation] no-docstring-rgx=^(?!__init__$)_ ``` **Additional details:** Both docstrings are acceptable but not both at the same time. **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### named-expr-without-context / W0131 **Message emitted:** **Named expression used without context** **Description:** *Emitted if named expression is used to do a regular assignment outside a context like if, for, while, or a comprehension.* **Problematic code:** ``` (a := 42) # [named-expr-without-context] ``` **Correct code:** ``` if a := 42: print("Success") ``` Created by the basic \ checker. ### nan-comparison / W0177 **Message emitted:** **Comparison %s should be %s** **Description:** *Used when an expression is compared to NaN values like numpy.NaN and float('nan').* **Problematic code:** ``` import numpy as np def both_nan(x, y) -> bool: return x == np.NaN and y == float("nan") # [nan-comparison, nan-comparison] ``` **Correct code:** ``` import numpy as np def both_nan(x, y) -> bool: return np.isnan(x) and np.isnan(y) ``` Created by the basic \ checker. ### nested-min-max / W3301 **Message emitted:** **Do not use nested call of '%s'; it's possible to do '%s' instead** **Description:** *Nested calls \`\`min(1, min(2, 3))\`\` can be rewritten as \`\`min(1, 2, 3)\`\`.* **Problematic code:** ``` print(min(1, min(2, 3))) # [nested-min-max] ``` **Correct code:** ``` print(min(1, 2, 3)) ``` Created by the nested\_min\_max \ checker. ### non-ascii-file-name / W2402 **Message emitted:** **%s name "%s" contains a non-ASCII character.** **Description:** *Under python 3.5, PEP 3131 allows non-ascii identifiers, but not non-ascii file names.Since Python 3.5, even though Python supports UTF-8 files, some editors or tools don't.* **Problematic code:** **bàd.py**: ``` # [non-ascii-file-name] ``` **not\_bétter.py**: ``` # [non-ascii-file-name] ``` **Correct code:** **\_\_init\_\_.py**: ``` ``` **bad.py**: ``` ``` **not\_better.py**: ``` ``` **Related links:** - • PEP 489 \ - • PEP 672 \ - • Python issue 20485 \ Created by the nonascii-checker \ checker. ### non-parent-init-called / W0233 **Message emitted:** **\_\_init\_\_ method from a non direct base class %r is called** **Description:** *Used when an \_\_init\_\_ method is called on a class which is not in the direct ancestors for the analysed class.* **Problematic code:** ``` class Animal: def __init__(self): self.is_multicellular = True class Vertebrate(Animal): def __init__(self): super().__init__() self.has_vertebrae = True class Cat(Vertebrate): def __init__(self): Animal.__init__(self) # [non-parent-init-called] self.is_adorable = True ``` **Correct code:** ``` class Animal: def __init__(self): self.is_multicellular = True class Vertebrate(Animal): def __init__(self): super().__init__() self.has_vertebrae = True class Cat(Vertebrate): def __init__(self): super().__init__() self.is_adorable = True ``` Created by the classes \ checker. ### non-str-assignment-to-dunder-name / W1115 **Message emitted:** **Non-string value assigned to \_\_name\_\_** **Description:** *Emitted when a non-string value is assigned to \_\_name\_\_* **Problematic code:** ``` class Fruit: pass Fruit.__name__ = 1 # [non-str-assignment-to-dunder-name] ``` **Correct code:** ``` class Fruit: pass Fruit.__name__ = "FRUIT" ``` Created by the typecheck \ checker. ### overlapping-except / W0714 **Message emitted:** **Overlapping exceptions (%s)** **Description:** *Used when exceptions in handler overlap or are identical* **Problematic code:** ``` def divide_x_by_y(x: float, y: float): try: print(x / y) except (ArithmeticError, FloatingPointError) as e: # [overlapping-except] print(f"There was an issue: {e}") ``` **Correct code:** **less\_generic\_first.py**: ``` def divide_x_by_y(x: float, y: float): try: print(x / y) except FloatingPointError as e: print(f"There was a FloatingPointError: {e}") except ArithmeticError as e: # FloatingPointError were already caught at this point print(f"There was an OverflowError or a ZeroDivisionError: {e}") ``` **only\_generic.py**: ``` def divide_x_by_y(x: float, y: float): try: print(x / y) except ArithmeticError as e: print( f"There was an OverflowError, a ZeroDivisionError or a FloatingPointError: {e}" ) ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.overlapping_exceptions, ``` **Related links:** - • Exception hierarchy \ **Note:** This message is emitted by the optional 'overlap-except' \<#pylint-extensions-overlapping-exceptions\> checker, which requires the **pylint.extensions.overlapping\_exceptions** plugin to be loaded. Created by the overlap-except \ checker. ### overridden-final-method / W0239 **Message emitted:** **Method %r overrides a method decorated with typing.final which is defined in class %r** **Description:** *Used when a method decorated with typing.final has been overridden.* **Problematic code:** ``` from typing import final class Animal: @final def can_breathe(self): return True class Cat(Animal): def can_breathe(self): # [overridden-final-method] pass ``` **Correct code:** ``` from typing import final class Animal: @final def can_breathe(self): return True class Cat(Animal): def can_purr(self): return True ``` **Configuration file:** ``` [MAIN] py-version=3.8 ``` **Additional details:** The message can't be emitted when using Python \< 3.8. **Related links:** - • PEP 591 \ Created by the classes \ checker. ### pointless-exception-statement / W0133 **Message emitted:** **Exception statement has no effect** **Description:** *Used when an exception is created without being assigned, raised or returned for subsequent use elsewhere.* **Problematic code:** ``` Exception("This exception is a statement.") # [pointless-exception-statement] ``` **Correct code:** ``` raise Exception("This will raise.") ``` Created by the basic \ checker. ### pointless-statement / W0104 **Message emitted:** **Statement seems to have no effect** **Description:** *Used when a statement doesn't have (or at least seems to) any effect.* **Problematic code:** ``` [1, 2, 3] # [pointless-statement] ``` **Correct code:** ``` NUMBERS = [1, 2, 3] print(NUMBERS) ``` Created by the basic \ checker. ### pointless-string-statement / W0105 **Message emitted:** **String statement has no effect** **Description:** *Used when a string is used as a statement (which of course has no effect). This is a particular case of W0104 with its own message so you can easily disable it if you're using those strings as documentation, instead of comments.* **Problematic code:** ``` """This is a docstring which describes the module""" """This is not a docstring""" # [pointless-string-statement] ``` **Correct code:** ``` """This is a docstring which describes the module""" # This is comment which describes a particular part of the module. ``` **Related links:** - • Discussion thread re: docstrings on assignments \ Created by the basic \ checker. ### possibly-unused-variable / W0641 **Message emitted:** **Possibly unused variable %r** **Description:** *Used when a variable is defined but might not be used. The possibility comes from the fact that locals() might be used, which could consume or not the said variable* **Problematic code:** ``` def choose_fruits(fruits): print(fruits) color = "red" # [possibly-unused-variable] return locals() ``` **Correct code:** ``` def choose_fruits(fruits): current_locals = locals() print(fruits) color = "red" print(color) return current_locals ``` Created by the variables \ checker. ### preferred-module / W0407 **Message emitted:** **Prefer importing %r instead of %r** **Description:** *Used when a module imported has a preferred replacement module.* **Problematic code:** ``` import urllib # [preferred-module] ``` **Correct code:** ``` import requests ``` **Configuration file:** ``` [IMPORTS] preferred-modules=urllib:requests, ``` Created by the imports \ checker. ### protected-access / W0212 **Message emitted:** **Access to a protected member %s of a client class** **Description:** *Used when a protected member (i.e. class member with a name beginning with an underscore) is accessed outside the class or a descendant of the class where it's defined.* **Problematic code:** ``` class Worm: def __swallow(self): pass jim = Worm() jim.__swallow() # [protected-access] ``` **Correct code:** ``` class Worm: def __swallow(self): pass def eat(self): return self.__swallow() jim = Worm() jim.eat() ``` Created by the classes \ checker. ### raise-missing-from / W0707 **Message emitted:** **Consider explicitly re-raising using %s'%s from %s'** **Description:** *Python's exception chaining shows the traceback of the current exception, but also of the original exception. When you raise a new exception after another exception was caught it's likely that the second exception is a friendly re-wrapping of the first exception. In such cases \`raise from\` provides a better link between the two tracebacks in the final error.* **Problematic code:** ``` try: 1 / 0 except ZeroDivisionError as e: raise ValueError("Rectangle Area cannot be zero") # [raise-missing-from] ``` **Correct code:** ``` try: 1 / 0 except ZeroDivisionError as e: raise ValueError("Rectangle Area cannot be zero") from e ``` **Related links:** - • PEP 3134 \ Created by the exceptions \ checker. ### raising-format-tuple / W0715 **Message emitted:** **Exception arguments suggest string formatting might be intended** **Description:** *Used when passing multiple arguments to an exception constructor, the first of them a string literal containing what appears to be placeholders intended for formatting* **Problematic code:** ``` raise RuntimeError("This looks wrong %s %s", ("a", "b")) # [raising-format-tuple] ``` **Correct code:** ``` raise RuntimeError("This looks wrong %s %s" % ("a", "b")) ``` Created by the exceptions \ checker. ### redeclared-assigned-name / W0128 **Message emitted:** **Redeclared variable %r in assignment** **Description:** *Emitted when we detect that a variable was redeclared in the same assignment.* **Problematic code:** ``` FIRST, FIRST = (1, 2) # [redeclared-assigned-name] ``` **Correct code:** ``` FIRST, SECOND = (1, 2) ``` Created by the basic \ checker. ### redefined-builtin / W0622 **Message emitted:** **Redefining built-in %r** **Description:** *Used when a variable or function override a built-in.* **Problematic code:** ``` def map(): # [redefined-builtin] pass ``` **Correct code:** ``` def map_iterable(): pass ``` **Additional details:** The allowed-redefined-builtins \<#variables-options\> option lets you specify names that are permitted to shadow built-ins. However, this option is not effective for redefinitions at the module level or for global variables. For example: Module-Level Redefinitions: ``` # module_level_redefine.py id = 1 # Shadows the built-in `id` ``` Global Variable Redefinitions: ``` # global_variable_redefine.py def my_func(): global len len = 1 # Shadows the built-in `len` ``` Rationale: Shadowing built-ins at the global scope is discouraged because it obscures their behavior throughout the entire module, increasing the risk of subtle bugs when the built-in is needed elsewhere. In contrast, local redefinitions are acceptable as their impact is confined to a specific scope, reducing unintended side effects and simplifying debugging. Created by the variables \ checker. ### redefined-loop-name / W2901 **Message emitted:** **Redefining %r from loop (line %s)** **Description:** *Used when a loop variable is overwritten in the loop body.* **Problematic code:** ``` def normalize_names(names): for name in names: name = name.lower() # [redefined-loop-name] ``` **Correct code:** ``` def normalize_names(names): for name in names: lowercased_name = name.lower() ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.redefined_loop_name, ``` **Note:** This message is emitted by the optional 'redefined-loop-name' \<#pylint-extensions-redefined-loop-name\> checker, which requires the **pylint.extensions.redefined\_loop\_name** plugin to be loaded. Created by the redefined-loop-name \ checker. ### redefined-outer-name / W0621 **Message emitted:** **Redefining name %r from outer scope (line %s)** **Description:** *Used when a variable's name hides a name defined in an outer scope or except handler.* **Problematic code:** ``` count = 10 def count_it(count): # [redefined-outer-name] for i in range(count): print(i) ``` **Correct code:** ``` count = 10 def count_it(limit): for i in range(limit): print(i) ``` **Additional details:** A common issue is that this message is triggered when using *pytest* fixtures \: ``` import pytest @pytest.fixture def setup(): ... def test_something(setup): # [redefined-outer-name] ... ``` One solution to this problem is to explicitly name the fixture: ``` @pytest.fixture(name="setup") def setup_fixture(): ... ``` Alternatively *pylint* plugins like pylint-pytest \ can be used. Created by the variables \ checker. ### redefined-slots-in-subclass / W0244 **Message emitted:** **Redefined slots %r in subclass** **Description:** *Used when a slot is re-defined in a subclass.* **Problematic code:** ``` class Base: __slots__ = ("a", "b") class Subclass(Base): __slots__ = ("a", "d") # [redefined-slots-in-subclass] ``` **Correct code:** ``` class Base: __slots__ = ("a", "b") class Subclass(Base): __slots__ = ("d",) ``` Created by the classes \ checker. ### redundant-returns-doc / W9008 **Message emitted:** **Redundant returns documentation** **Description:** *Please remove the return/rtype documentation from this method.* **Problematic code:** ``` def print_fruits(fruits): # [redundant-returns-doc] """Print list of fruits Returns ------- str """ print(fruits) return None ``` **Correct code:** ``` def print_fruits(fruits): """Print list of fruits Returns ------- str """ print(fruits) return ",".join(fruits) ``` **Configuration file:** ``` [MAIN] load-plugins = pylint.extensions.docparams ``` **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### redundant-u-string-prefix / W1406 **Message emitted:** **The u prefix for strings is no longer necessary in Python \>=3.0** **Description:** *Used when we detect a string with a u prefix. These prefixes were necessary in Python 2 to indicate a string was Unicode, but since Python 3.0 strings are Unicode by default.* **Problematic code:** ``` def print_fruit(): print(u"Apple") # [redundant-u-string-prefix] ``` **Correct code:** ``` def print_fruit(): print("Apple") ``` Created by the string \ checker. ### redundant-unittest-assert / W1503 **Message emitted:** **Redundant use of %s with constant value %r** **Description:** *The first argument of assertTrue and assertFalse is a condition. If a constant is passed as parameter, that condition will be always true. In this case a warning should be emitted.* **Problematic code:** ``` import unittest class DummyTestCase(unittest.TestCase): def test_dummy(self): self.assertTrue("foo") # [redundant-unittest-assert] ``` **Correct code:** ``` import unittest class DummyTestCase(unittest.TestCase): def test_dummy(self): actual = "test_result" self.assertEqual(actual, "expected") ``` **Additional details:** Directly asserting a string literal will always pass. The solution is to test something that could fail, or not assert at all. For assertions using **assert** there are similar messages: assert-on-string-literal / W0129 \<#assert-on-string-literal\> and assert-on-tuple / W0199 \<#assert-on-tuple\>. **Related links:** - • Tests without assertion \ - • Testing that there is no error raised \ - • Parametrizing conditional raising \ Created by the stdlib \ checker. ### redundant-yields-doc / W9010 **Message emitted:** **Redundant yields documentation** **Description:** *Please remove the yields documentation from this method.* **Problematic code:** ``` def give_fruits(fruits): # [redundant-yields-doc] """Something about fruits Yields ------- list fruits """ return fruits ``` **Correct code:** ``` def give_fruits(fruits): """Something about fruits Yields ------- str fruit """ for fruit in fruits: yield fruit ``` **Configuration file:** ``` [MAIN] load-plugins = pylint.extensions.docparams ``` **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### reimported / W0404 **Message emitted:** **Reimport %r (imported line %s)** **Description:** *Used when a module is imported more than once.* **Problematic code:** ``` import re import re # [reimported] ``` **Correct code:** ``` import re ``` Created by the imports \ checker. ### return-in-finally / W0134 **Message emitted:** **'return' shadowed by the 'finally' clause.** **Description:** *Emitted when a 'return' statement is found in a 'finally' block. This will overwrite the return value of a function and should be avoided.* **Problematic code:** ``` def second_favorite(): fruits = ["kiwi", "pineapple"] try: return fruits[1] finally: # because of this `return` statement, this function will always return "kiwi" return fruits[0] # [return-in-finally] ``` **Correct code:** ``` def second_favorite(): fruits = ["kiwi", "pineapple"] try: return fruits[1] except KeyError: ... return fruits[0] ``` **Related links:** - • Python 3 docs 'finally' clause \ - • PEP 765 - Disallow return/break/continue that exit a finally block \ Created by the basic \ checker. ### self-assigning-variable / W0127 **Message emitted:** **Assigning the same variable %r to itself** **Description:** *Emitted when we detect that a variable is assigned to itself* **Problematic code:** ``` year = 2000 year = year # [self-assigning-variable] ``` **Correct code:** ``` year = 2000 ``` **Related links:** - • Python assignment statement \ Created by the basic \ checker. ### self-cls-assignment / W0642 **Message emitted:** **Invalid assignment to %s in method** **Description:** *Invalid assignment to self or cls in instance or class method respectively.* **Problematic code:** ``` class Fruit: @classmethod def list_fruits(cls): cls = "apple" # [self-cls-assignment] def print_color(self, *colors): self = "red" # [self-cls-assignment] color = colors[1] print(color) ``` **Correct code:** ``` class Fruit: @classmethod def list_fruits(cls): fruit = "apple" print(fruit) def print_color(self, *colors): color = colors[1] print(color) ``` Created by the variables \ checker. ### shadowed-import / W0416 **Message emitted:** **Shadowed %r (imported line %s)** **Description:** *Used when a module is aliased with a name that shadows another import.* **Problematic code:** ``` from pathlib import Path import FastAPI.Path as Path # [shadowed-import] ``` **Correct code:** ``` from pathlib import Path import FastAPI.Path as FastApiPath ``` Created by the imports \ checker. ### shallow-copy-environ / W1507 **Message emitted:** **Using copy.copy(os.environ). Use os.environ.copy() instead.** **Description:** *os.environ is not a dict object but proxy object, so shallow copy has still effects on original object. See https://bugs.python.org/issue15373 for reference.* **Problematic code:** ``` import copy import os copied_env = copy.copy(os.environ) # [shallow-copy-environ] ``` **Correct code:** ``` import os copied_env = os.environ.copy() ``` Created by the stdlib \ checker. ### signature-differs / W0222 **Message emitted:** **Signature differs from %s %r method** **Description:** *Used when a method signature is different than in the implemented interface or in an overridden method.* **Problematic code:** ``` class Animal: def run(self, distance=0): print(f"Ran {distance} km!") class Dog(Animal): def run(self, distance): # [signature-differs] super(Animal, self).run(distance) print("Fetched that stick, wuff !") ``` **Correct code:** ``` class Animal: def run(self, distance=0): print(f"Ran {distance} km!") class Dog(Animal): def run(self, distance=0): super(Animal, self).run(distance) print("Fetched that stick, wuff !") ``` Created by the classes \ checker. ### subclassed-final-class / W0240 **Message emitted:** **Class %r is a subclass of a class decorated with typing.final: %r** **Description:** *Used when a class decorated with typing.final has been subclassed.* **Problematic code:** ``` from typing import final @final class PlatypusData: """General Platypus data.""" average_length = 46 average_body_temperature = 32 class FluorescentPlaytipus(PlatypusData): # [subclassed-final-class] """Playtipus with fluorescent fur.""" ``` **Correct code:** ``` from typing import final @final class PlatypusData: """General Platypus data.""" average_length = 46 average_body_temperature = 32 def print_average_length_platypus(): output = f"The average length of a platypus is: {PlatypusData.average_length}cm" print(output) ``` **Configuration file:** ``` [MAIN] py-version=3.8 ``` **Additional details:** This message is emitted when a class which is decorated with *final* is subclassed; the decorator indicates that the class is not intended to be extended. Note this message can't be emitted when using Python \< 3.8. **Related links:** - • PEP 591 \ Created by the classes \ checker. ### subprocess-popen-preexec-fn / W1509 **Message emitted:** **Using preexec\_fn keyword which may be unsafe in the presence of threads** **Description:** *The preexec\_fn parameter is not safe to use in the presence of threads in your application. The child process could deadlock before exec is called. If you must use it, keep it trivial! Minimize the number of libraries you call into. See https://docs.python.org/3/library/subprocess.html#popen-constructor* **Problematic code:** ``` import subprocess def foo(): pass subprocess.Popen(preexec_fn=foo) # [subprocess-popen-preexec-fn] ``` **Correct code:** ``` import subprocess subprocess.Popen() ``` Created by the stdlib \ checker. ### subprocess-run-check / W1510 **Message emitted:** **'subprocess.run' used without explicitly defining the value for 'check'.** **Description:** *The \`\`check\`\` keyword is set to False by default. It means the process launched by \`\`subprocess.run\`\` can exit with a non-zero exit code and fail silently. It's better to set it explicitly to make clear what the error-handling behavior is.* **Problematic code:** ``` import subprocess proc = subprocess.run(["ls"]) # [subprocess-run-check] ``` **Correct code:** ``` import subprocess proc = subprocess.run(["ls"], check=False) ``` **Related links:** - • subprocess.run documentation \ Created by the stdlib \ checker. ### super-init-not-called / W0231 **Message emitted:** **\_\_init\_\_ method from base class %r is not called** **Description:** *Used when an ancestor class method has an \_\_init\_\_ method which is not called by a derived class.* **Problematic code:** ``` class Fruit: def __init__(self, name="fruit"): self.name = name print("Creating a {self.name}") class Apple(Fruit): def __init__(self): # [super-init-not-called] print("Creating an apple") ``` **Correct code:** ``` class Fruit: def __init__(self, name="fruit"): self.name = name print("Creating a {self.name}") class Apple(Fruit): def __init__(self): super().__init__("apple") ``` Created by the classes \ checker. ### super-without-brackets / W0245 **Message emitted:** **Super call without brackets** **Description:** *Used when a call to super does not have brackets and thus is not an actual call and does not work as expected.* **Problematic code:** ``` class Soup: @staticmethod def temp(): print("Soup is hot!") class TomatoSoup(Soup): @staticmethod def temp(): super.temp() # [super-without-brackets] print("But tomato soup is even hotter!") ``` **Correct code:** ``` class Soup: @staticmethod def temp(): print("Soup is hot!") class TomatoSoup(Soup): @staticmethod def temp(): super().temp() print("But tomato soup is even hotter!") ``` Created by the classes \ checker. ### too-many-try-statements / W0717 **Message emitted:** **%s** **Description:** *Try clause contains too many statements.* **Problematic code:** ``` FRUITS = {"apple": 1, "orange": 10} def pick_fruit(name): try: # [too-many-try-statements] count = FRUITS[name] count += 1 print(f"Got fruit count {count}") except KeyError: return ``` **Correct code:** ``` FRUITS = {"apple": 1, "orange": 10} def pick_fruit(name): try: count = FRUITS[name] except KeyError: return count += 1 print(f"Got fruit count {count}") ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.broad_try_clause, ``` **Note:** This message is emitted by the optional 'broad\_try\_clause' \<#pylint-extensions-broad-try-clause\> checker, which requires the **pylint.extensions.broad\_try\_clause** plugin to be loaded. Created by the broad\_try\_clause \ checker. ### try-except-raise / W0706 **Message emitted:** **The except handler raises immediately** **Description:** *Used when an except handler uses raise as its first or only operator. This is useless because it raises back the exception immediately. Remove the raise operator or the entire try-except-raise block!* **Problematic code:** ``` try: 1 / 0 except ZeroDivisionError as e: # [try-except-raise] raise ``` **Correct code:** **remove\_try\_except.py**: ``` # The try except might be removed entirely: 1 / 0 ``` **specialized\_exception.py**: ``` # Another more detailed exception can be raised: try: 1 / 0 except ZeroDivisionError as e: raise ValueError("The area of the rectangle cannot be zero") from e ``` **Additional details:** There is a legitimate use case for re-raising immediately. E.g. with the following inheritance tree: ``` +-- ArithmeticError +-- FloatingPointError +-- OverflowError +-- ZeroDivisionError ``` The following code shows valid case for re-raising exception immediately: ``` def execute_calculation(a, b): try: return some_calculation(a, b) except ZeroDivisionError: raise except ArithmeticError: return float('nan') ``` The pylint is able to detect this case and does not produce error. Created by the exceptions \ checker. ### unbalanced-dict-unpacking / W0644 **Message emitted:** **Possible unbalanced dict unpacking with %s: left side has %d label%s, right side has %d value%s** **Description:** *Used when there is an unbalanced dict unpacking in assignment or for loop* **Problematic code:** ``` FRUITS = {"apple": 2, "orange": 3, "mellon": 10} for fruit, price in FRUITS.values(): # [unbalanced-dict-unpacking] print(fruit) ``` **Correct code:** ``` FRUITS = {"apple": 2, "orange": 3, "mellon": 10} for fruit, price in FRUITS.items(): print(fruit) ``` Created by the variables \ checker. ### undefined-loop-variable / W0631 **Message emitted:** **Using possibly undefined loop variable %r** **Description:** *Used when a loop variable (i.e. defined by a for loop or a list comprehension or a generator expression) is used outside the loop.* **Problematic code:** ``` def find_even_number(numbers): for x in numbers: if x % 2 == 0: break return x # [undefined-loop-variable] ``` **Correct code:** ``` def find_even_number(numbers): for x in numbers: if x % 2: return x return None ``` Created by the variables \ checker. ### unnecessary-ellipsis / W2301 **Message emitted:** **Unnecessary ellipsis constant** **Description:** *Used when the ellipsis constant is encountered and can be avoided. A line of code consisting of an ellipsis is unnecessary if there is a docstring on the preceding line or if there is a statement in the same scope.* **Problematic code:** ``` def my_function(): """My docstring""" ... # [unnecessary-ellipsis] ``` **Correct code:** ``` def my_function(): """My docstring""" ``` Created by the unnecessary\_ellipsis \ checker. ### unnecessary-lambda / W0108 **Message emitted:** **Lambda may not be necessary** **Description:** *Used when the body of a lambda expression is a function call on the same argument list as the lambda itself; such lambda expressions are in all but a few cases replaceable with the function being called in the body of the lambda.* **Problematic code:** **pandas.py**: ``` df.apply(lambda x: str(x)) # [unnecessary-lambda] ``` **print.py**: ``` function = lambda x: print(x) # [unnecessary-lambda] function("Hello world !") ``` **Correct code:** **pandas.py**: ``` df.apply(str) ``` **print.py**: ``` print("Hello world !") ``` Created by the basic \ checker. ### unnecessary-pass / W0107 **Message emitted:** **Unnecessary pass statement** **Description:** *Used when a "pass" statement can be removed without affecting the behaviour of the code.* **Problematic code:** ``` class DataEntryError(Exception): """This exception is raised when a user has provided incorrect data.""" pass # [unnecessary-pass] ``` **Correct code:** ``` class DataEntryError(Exception): """This exception is raised when a user has provided incorrect data.""" ``` Created by the basic \ checker. ### unnecessary-semicolon / W0301 **Message emitted:** **Unnecessary semicolon** **Description:** *Used when a statement is ended by a semi-colon (";"), which isn't necessary (that's python, not C ;).* **Problematic code:** ``` print("Hello World!"); # [unnecessary-semicolon] ``` **Correct code:** ``` print("Hello World!") ``` Created by the format \ checker. ### unreachable / W0101 **Message emitted:** **Unreachable code** **Description:** *Used when there is some code behind a "return" or "raise" statement, which will never be accessed.* **Problematic code:** ``` def say_hello(): return True print("Hello World!, Outside function.") # [unreachable] ``` **Correct code:** ``` def say_hello(): print("Hello World!, Inside function.") return True ``` Created by the basic \ checker. ### unspecified-encoding / W1514 **Message emitted:** **Using open without explicitly specifying an encoding** **Description:** *It is better to specify an encoding when opening documents. Using the system default implicitly can create problems on other operating systems. See https://peps.python.org/pep-0597/* **Problematic code:** ``` def foo(file_path): with open(file_path) as file: # [unspecified-encoding] contents = file.read() ``` **Correct code:** ``` def foo(file_path): with open(file_path, encoding="utf-8") as file: contents = file.read() ``` Created by the stdlib \ checker. ### unused-argument / W0613 **Message emitted:** **Unused argument %r** **Description:** *Used when a function or method argument is not used.* **Problematic code:** ``` def print_point(x, y): # [unused-argument] print(f"Point is located at {x},{x}") ``` **Correct code:** ``` def print_point(x, y): print(f"Point is located at {x},{y}") ``` Created by the variables \ checker. ### unused-format-string-argument / W1304 **Message emitted:** **Unused format argument %r** **Description:** *Used when a PEP 3101 format string that uses named fields is used with an argument that is not required by the format string.* **Problematic code:** ``` print("{x} {y}".format(x=1, y=2, z=3)) # [unused-format-string-argument] ``` **Correct code:** **add\_format\_target.py**: ``` print("{x} {y} {z}".format(x=1, y=2, z=3)) ``` **remove\_unused\_args.py**: ``` print("{x} {y}".format(x=1, y=2)) ``` Created by the string \ checker. ### unused-format-string-key / W1301 **Message emitted:** **Unused key %r in format string dictionary** **Description:** *Used when a format string that uses named conversion specifiers is used with a dictionary that contains keys not required by the format string.* **Problematic code:** ``` "The quick %(color)s fox jumps over the lazy dog." % { "color": "brown", "action": "hops", } # -4: [unused-format-string-key] ``` **Correct code:** ``` "The quick %(color)s fox %(action)s over the lazy dog." % { "color": "brown", "action": "hops", } ``` Created by the string \ checker. ### unused-import / W0611 **Message emitted:** **Unused %s** **Description:** *Used when an imported module or variable is not used.* **Problematic code:** ``` from logging import getLogger from pathlib import Path # [unused-import] LOGGER = getLogger(__name__) ``` **Correct code:** ``` from logging import getLogger LOGGER = getLogger(__name__) ``` **Additional details:** By default, this check is skipped for **\_\_init\_\_.py** files, as they often contain imports from submodules for the convenience of end users. While these imports are not used within **\_\_init\_\_.py**, they serve the purpose of providing intuitive import paths for the module's important classes and constants. **Related links:** - • \--init-import \<#variables-options\> Created by the variables \ checker. ### unused-private-member / W0238 **Message emitted:** **Unused private member \`%s.%s\`** **Description:** *Emitted when a private member of a class is defined but not used.* **Problematic code:** ``` class Fruit: FRUITS = {"apple": "red", "orange": "orange"} def __print_color(self): # [unused-private-member] pass ``` **Correct code:** ``` class Fruit: FRUITS = {"apple": "red", "orange": "orange"} def __print_color(self, name, color): print(f"{name}: {color}") def print(self): for fruit, color in self.FRUITS.items(): self.__print_color(fruit, color) ``` Created by the classes \ checker. ### unused-variable / W0612 **Message emitted:** **Unused variable %r** **Description:** *Used when a variable is defined but not used.* **Problematic code:** ``` def print_fruits(): fruit1 = "orange" fruit2 = "apple" # [unused-variable] print(fruit1) ``` **Correct code:** ``` def print_fruits(): fruit1 = "orange" fruit2 = "apple" print(fruit1, fruit2) ``` Created by the variables \ checker. ### unused-wildcard-import / W0614 **Message emitted:** **Unused import(s) %s from wildcard import of %s** **Description:** *Used when an imported module or variable is not used from a \`'from X import \*'\` style import.* **Problematic code:** ``` from abc import * # [unused-wildcard-import] class Animal(ABC): ... ``` **Correct code:** ``` from abc import ABC class Animal(ABC): ... ``` Created by the variables \ checker. ### useless-else-on-loop / W0120 **Message emitted:** **Else clause on loop without a break statement, remove the else and de-indent all the code inside it** **Description:** *Loops should only have an else clause if they can exit early with a break statement, otherwise the statements under else should be on the same scope as the loop itself.* **Problematic code:** ``` def find_even_number(numbers): for x in numbers: if x % 2 == 0: return x else: # [useless-else-on-loop] print("Did not find an even number") ``` **Correct code:** ``` def find_even_number(numbers): for x in numbers: if x % 2 == 0: return x print("Did not find an even number") ``` Created by the basic \ checker. ### useless-param-doc / W9019 **Message emitted:** **"%s" useless ignored parameter documentation** **Description:** *Please remove the ignored parameter documentation.* **Problematic code:** ``` def say_hello(_new: str) -> str: # [useless-param-doc] """say hello! :param _new: :return: comment """ return "hello" ``` **Correct code:** ``` def say_hello(_new: str) -> str: """say hello! :return: comment """ return "hello" ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.docparams, ``` **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### useless-parent-delegation / W0246 **Message emitted:** **Useless parent or super() delegation in method %r** **Description:** *Used whenever we can detect that an overridden method is useless, relying on parent or super() delegation to do the same thing as another method from the MRO.* **Problematic code:** ``` class Animal: def eat(self, food): print(f"Eating {food}") class Human(Animal): def eat(self, food): # [useless-parent-delegation] super(Human, self).eat(food) ``` **Correct code:** ``` class Animal: def eat(self, food): print(f"Eating {food}") class Human(Animal): """There is no need to override 'eat' it has the same signature as the implementation in Animal.""" ``` **Related links:** - • Stackoverflow explanation for 'useless-super-delegation' \ Created by the classes \ checker. ### useless-type-doc / W9020 **Message emitted:** **"%s" useless ignored parameter type documentation** **Description:** *Please remove the ignored parameter type documentation.* **Problematic code:** ``` def print_fruit(fruit, _): # [useless-type-doc] """docstring ... Args: fruit (str): A fruit. _ (float): Another argument. """ print(fruit) ``` **Correct code:** ``` def print_fruit(fruit): """docstring ... Args: fruit (str): A fruit. """ print(fruit) ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.docparams, ``` **Note:** This message is emitted by the optional 'parameter\_documentation' \<#pylint-extensions-docparams\> checker, which requires the **pylint.extensions.docparams** plugin to be loaded. Created by the parameter\_documentation \ checker. ### useless-with-lock / W2101 **Message emitted:** **'%s()' directly created in 'with' has no effect** **Description:** *Used when a new lock instance is created by using with statement which has no effect. Instead, an existing instance should be used to acquire lock.* **Problematic code:** ``` import threading with threading.Lock(): # [useless-with-lock] print("Make your bed.") with threading.Lock(): # [useless-with-lock] print("Sleep in it") ``` **Correct code:** ``` import threading lock = threading.Lock() with lock: print("Make your bed.") with lock: print("Sleep in it.") ``` Created by the threading \ checker. ### using-assignment-expression-in-unsupported-version / W2605 **Message emitted:** **Assignment expression is not supported by all versions included in the py-version setting** **Description:** *Used when the py-version set by the user is lower than 3.8 and pylint encounters an assignment expression (walrus) operator.* **Problematic code:** ``` import random # +1: [using-assignment-expression-in-unsupported-version] if zero_or_one := random.randint(0, 1): assert zero_or_one == 1 ``` **Correct code:** ``` import random zero_or_one = random.randint(0, 1) if zero_or_one: assert zero_or_one == 1 ``` **Configuration file:** ``` [main] py-version=3.7 ``` **Additional details:** The assignment expression (walrus) operator (*:=*) was introduced in Python 3.8; to use it, please use a more recent version of Python. Created by the unsupported\_version \ checker. ### using-constant-test / W0125 **Message emitted:** **Using a conditional statement with a constant value** **Description:** *Emitted when a conditional statement (If or ternary if) uses a constant value for its test. This might not be what the user intended to do.* **Problematic code:** ``` if 0: # [using-constant-test] print("This code is never executed.") if 1: # [using-constant-test] print("This code is always executed.") ``` **Correct code:** ``` print("This code is always executed.") ``` Created by the basic \ checker. ### using-exception-groups-in-unsupported-version / W2603 **Message emitted:** **Exception groups are not supported by all versions included in the py-version setting** **Description:** *Used when the py-version set by the user is lower than 3.11 and pylint encounters \`\`except\*\`\` or \`ExceptionGroup\`\`.* **Problematic code:** ``` def f(): excs = [OSError("error 1"), SystemError("error 2")] # +1: [using-exception-groups-in-unsupported-version] raise ExceptionGroup("there were problems", excs) try: # [using-exception-groups-in-unsupported-version] f() except* OSError as e: print("There were OSErrors") except* SystemError as e: print("There were SystemErrors") ``` **Correct code:** ``` def f(): raise OSError("error 1") try: f() except OSError as e: print("There were OSErrors") except SystemError as e: print("There were SystemErrors") ``` **Configuration file:** ``` [main] py-version=3.10 ``` **Additional details:** Exception groups were introduced in Python 3.11; to use it, please use a more recent version of Python. Created by the unsupported\_version \ checker. ### using-f-string-in-unsupported-version / W2601 **Message emitted:** **F-strings are not supported by all versions included in the py-version setting** **Description:** *Used when the py-version set by the user is lower than 3.6 and pylint encounters an f-string.* **Problematic code:** ``` f"python {3.5} is past end of life" # [using-f-string-in-unsupported-version] ``` **Correct code:** ``` "python {} is past end of life".format(3.5) ``` **Configuration file:** ``` [main] py-version=3.5 ``` **Additional details:** f-strings were introduced in Python version 3.6; to use them, please use a more recent version of Python. Created by the unsupported\_version \ checker. ### using-final-decorator-in-unsupported-version / W2602 **Message emitted:** **typing.final is not supported by all versions included in the py-version setting** **Description:** *Used when the py-version set by the user is lower than 3.8 and pylint encounters a \`\`typing.final\`\` decorator.* **Problematic code:** ``` from typing import final @final # [using-final-decorator-in-unsupported-version] class Playtypus(Animal): @final # [using-final-decorator-in-unsupported-version] def lay_egg(self): ... ``` **Correct code:** ``` class Playtypus(Animal): def lay_egg(self): ... ``` **Configuration file:** ``` [main] py-version=3.7 ``` **Additional details:** The message is emitted when the **final** decorator is used with a Python version less than 3.8. The **final** decorator was introduced in Python version 3.8. **Related links:** - • PEP 591 \ Created by the unsupported\_version \ checker. ### using-generic-type-syntax-in-unsupported-version / W2604 **Message emitted:** **Generic type syntax (PEP 695) is not supported by all versions included in the py-version setting** **Description:** *Used when the py-version set by the user is lower than 3.12 and pylint encounters generic type syntax.* **Problematic code:** ``` type Vector = list[float] # [using-generic-type-syntax-in-unsupported-version] ``` **Correct code:** ``` from typing import TypeAlias Vector: TypeAlias = list[float] ``` **Configuration file:** ``` [main] py-version=3.11 ``` **Additional details:** Generic type syntax was introduced in Python 3.12; to use it, please use a more recent version of Python. Created by the unsupported\_version \ checker. ### using-positional-only-args-in-unsupported-version / W2606 **Message emitted:** **Positional-only arguments are not supported by all versions included in the py-version setting** **Description:** *Used when the py-version set by the user is lower than 3.8 and pylint encounters positional-only arguments.* **Problematic code:** ``` def add(x, y, /): # [using-positional-only-args-in-unsupported-version] return x + y ``` **Correct code:** ``` # pylint: disable=missing-function-docstring, missing-module-docstring def add(x, y): return x + y ``` **Configuration file:** ``` [main] py-version=3.7 ``` **Additional details:** Positional-only arguments were introduced in Python 3.8; to use them, please use a more recent version of Python. Created by the unsupported\_version \ checker. ### while-used / W0149 **Message emitted:** **Used \`while\` loop** **Description:** *Unbounded \`while\` loops can often be rewritten as bounded \`for\` loops. Exceptions can be made for cases such as event loops, listeners, etc.* **Problematic code:** ``` import requests def fetch_data(): i = 1 while i < 6: # [while-used] print(f"Attempt {i}...") try: return requests.get("https://example.com/data") except requests.exceptions.RequestException: pass i += 1 ``` **Correct code:** ``` import requests def fetch_data(): for i in range(1, 6): print(f"Attempt {i}...") try: return requests.get("https://example.com/data") except requests.exceptions.RequestException: pass ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.while_used ``` **Related links:** - • Stackoverflow discussion \ **Note:** This message is emitted by the optional 'while\_used' \<#pylint-extensions-while-used\> checker, which requires the **pylint.extensions.while\_used** plugin to be loaded. Created by the while\_used \ checker. ### wildcard-import / W0401 **Message emitted:** **Wildcard import %s** **Description:** *Used when \`from module import \*\` is detected.* **Problematic code:** ``` from abc import * # [wildcard-import] ``` **Correct code:** ``` # Either import module or # only import required objects from module. import abc from abc import ABC, abstractmethod ``` Created by the imports \ checker. ### wrong-exception-operation / W0716 **Message emitted:** **Invalid exception operation. %s** **Description:** *Used when an operation is done against an exception, but the operation is not valid for the exception in question. Usually emitted when having binary operations between exceptions in except handlers.* **Problematic code:** ``` try: 1 / 0 except ValueError + TypeError: # [wrong-exception-operation] pass ``` **Correct code:** ``` try: 1 / 0 except (ValueError, TypeError): pass ``` Created by the exceptions \ checker. All renamed messages in the warning category: ### broad-except / W0703 'broad-except' has been renamed. The new message can be found at: ### cache-max-size-none / W1517 'cache-max-size-none' has been renamed. The new message can be found at: ### implicit-str-concat-in-sequence / W1403 'implicit-str-concat-in-sequence' has been renamed. The new message can be found at: ### lru-cache-decorating-method / W1516 'lru-cache-decorating-method' has been renamed. The new message can be found at: ### old-assignment-from-none / W1111 'old-assignment-from-none' has been renamed. The new message can be found at: ### old-deprecated-argument / W1511 'old-deprecated-argument' has been renamed. The new message can be found at: ### old-deprecated-class / W1512 'old-deprecated-class' has been renamed. The new message can be found at: ### old-deprecated-decorator / W1513 'old-deprecated-decorator' has been renamed. The new message can be found at: ### old-deprecated-method / W1505 'old-deprecated-method' has been renamed. The new message can be found at: ### old-deprecated-module / W0402 'old-deprecated-module' has been renamed. The new message can be found at: ### old-empty-docstring / W0132 'old-empty-docstring' has been renamed. The new message can be found at: ### empty-docstring / C0112 **Message emitted:** **Empty %s docstring** **Description:** *Used when a module, function, class or method has an empty docstring (it would be too easy ;).* **Problematic code:** ``` def foo(): # [empty-docstring] """""" ``` **Correct code:** ``` def foo(): """A dummy description.""" ``` Created by the basic \ checker. ### old-missing-param-doc / W9003 'old-missing-param-doc' has been renamed. The new message can be found at: ### old-missing-returns-doc / W9007 'old-missing-returns-doc' has been renamed. The new message can be found at: ### old-missing-type-doc / W9004 'old-missing-type-doc' has been renamed. The new message can be found at: ### old-missing-yields-doc / W9009 'old-missing-yields-doc' has been renamed. The new message can be found at: ### old-non-iterator-returned-1 / W0234 'old-non-iterator-returned-1' has been renamed. The new message can be found at: ### old-unidiomatic-typecheck / W0154 'old-unidiomatic-typecheck' has been renamed. The new message can be found at: ### unidiomatic-typecheck / C0123 **Message emitted:** **Use isinstance() rather than type() for a typecheck.** **Description:** *The idiomatic way to perform an explicit typecheck in Python is to use isinstance(x, Y) rather than type(x) == Y, type(x) is Y. Though there are unusual situations where these give different results.* **Problematic code:** ``` test_score = {"Biology": 95, "History": 80} if type(test_score) is dict: # [unidiomatic-typecheck] pass ``` **Correct code:** ``` test_score = {"Biology": 95, "History": 80} if isinstance(test_score, dict): pass ``` **Related links:** - • Builtin function type() \ - • Builtin function isinstance() \ Created by the basic \ checker. ### old-unpacking-non-sequence / W0633 'old-unpacking-non-sequence' has been renamed. The new message can be found at: ### useless-super-delegation / W0235 'useless-super-delegation' has been renamed. The new message can be found at: ### Convention All messages in the convention category: ### bad-classmethod-argument / C0202 **Message emitted:** **Class method %s should have %s as first argument** **Description:** *Used when a class method has a first argument named differently than the value specified in valid-classmethod-first-arg option (default to "cls"), recommended to easily differentiate them from regular instance methods.* **Problematic code:** ``` class Klass: @classmethod def get_instance(self): # [bad-classmethod-argument] return self() ``` **Correct code:** ``` class Klass: @classmethod def get_instance(cls): return cls() ``` Created by the classes \ checker. ### bad-docstring-quotes / C0198 **Message emitted:** **Bad docstring quotes in %s, expected """, given %s** **Description:** *Used when a docstring does not have triple double quotes.* **Problematic code:** ``` def foo(): # [bad-docstring-quotes] "Docstring." return ``` **Correct code:** ``` def foo(): """Docstring.""" return ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.docstyle ``` **Additional details:** - **From *PEP 257*:** "For consistency, always use **"""triple double quotes"""** around docstrings." **Related links:** - • PEP 257 – Docstring Conventions \ **Note:** This message is emitted by the optional 'docstyle' \<#pylint-extensions-docstyle\> checker, which requires the **pylint.extensions.docstyle** plugin to be loaded. Created by the docstyle \ checker. ### bad-file-encoding / C2503 **Message emitted:** **PEP8 recommends UTF-8 as encoding for Python files** **Description:** *PEP8 recommends UTF-8 default encoding for Python files. See https://peps.python.org/pep-0008/#source-file-encoding* **Problematic code:** ``` # coding: latin_1 # [bad-file-encoding] ``` **Correct code:** ``` ``` Created by the unicode\_checker \ checker. ### bad-mcs-classmethod-argument / C0204 **Message emitted:** **Metaclass class method %s should have %s as first argument** **Description:** *Used when a metaclass class method has a first argument named differently than the value specified in valid-metaclass-classmethod-first-arg option (default to "mcs"), recommended to easily differentiate them from regular instance methods.* **Problematic code:** ``` class Meta(type): @classmethod def foo(some): # [bad-mcs-classmethod-argument] pass ``` **Correct code:** ``` class Meta(type): @classmethod def foo(mcs): pass ``` Created by the classes \ checker. ### bad-mcs-method-argument / C0203 **Message emitted:** **Metaclass method %s should have %s as first argument** **Description:** *Used when a metaclass method has a first argument named differently than the value specified in valid-classmethod-first-arg option (default to "cls"), recommended to easily differentiate them from regular instance methods.* **Problematic code:** ``` class Meta(type): def func(some): # [bad-mcs-method-argument] pass ``` **Correct code:** ``` class Meta(type): def func(cls): pass ``` Created by the classes \ checker. ### consider-iterating-dictionary / C0201 **Message emitted:** **Consider iterating the dictionary directly instead of calling .keys()** **Description:** *Emitted when the keys of a dictionary are iterated through the \`\`.keys()\`\` method or when \`\`.keys()\`\` is used for a membership check. It is enough to iterate through the dictionary itself, \`\`for key in dictionary\`\`. For membership checks, \`\`if key in dictionary\`\` is faster.* **Problematic code:** ``` FRUITS = {"apple": 1, "pear": 5, "peach": 10} for fruit in FRUITS.keys(): # [consider-iterating-dictionary] print(fruit) ``` **Correct code:** ``` FRUITS = {"apple": 1, "pear": 5, "peach": 10} for fruit in FRUITS: print(fruit) ``` Created by the refactoring \ checker. ### consider-using-any-or-all / C0501 **Message emitted:** **\`for\` loop could be \`%s\`** **Description:** *A for loop that checks for a condition and return a bool can be replaced with any or all.* **Problematic code:** **all\_even.py**: ``` def all_even(items): """Return True if the list contains all even numbers""" for item in items: # [consider-using-any-or-all] if not item % 2 == 0: return False return True ``` **any\_even.py**: ``` def any_even(items): """Return True if the list contains any even numbers""" for item in items: # [consider-using-any-or-all] if item % 2 == 0: return True return False ``` **Correct code:** **all\_even.py**: ``` def all_even(items): """Return True if the list contains all even numbers""" return all(item % 2 == 0 for item in items) ``` **any\_even.py**: ``` def any_even(items): """Return True if the list contains any even numbers""" return any(item % 2 == 0 for item in items) ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.for_any_all ``` **Note:** This message is emitted by the optional 'consider-using-any-or-all' \<#pylint-extensions-for-any-all\> checker, which requires the **pylint.extensions.for\_any\_all** plugin to be loaded. Created by the consider-using-any-or-all \ checker. ### consider-using-dict-items / C0206 **Message emitted:** **Consider iterating with .items()** **Description:** *Emitted when iterating over the keys of a dictionary and accessing the value by index lookup. Both the key and value can be accessed by iterating using the .items() method of the dictionary instead.* **Problematic code:** ``` ORCHESTRA = { "violin": "strings", "oboe": "woodwind", "tuba": "brass", "gong": "percussion", } for instrument in ORCHESTRA: # [consider-using-dict-items] print(f"{instrument}: {ORCHESTRA[instrument]}") ``` **Correct code:** ``` ORCHESTRA = { "violin": "strings", "oboe": "woodwind", "tuba": "brass", "gong": "percussion", } for instrument, section in ORCHESTRA.items(): print(f"{instrument}: {section}") ``` Created by the refactoring \ checker. ### consider-using-enumerate / C0200 **Message emitted:** **Consider using enumerate instead of iterating with range and len** **Description:** *Emitted when code that iterates with range and len is encountered. Such code can be simplified by using the enumerate builtin.* **Problematic code:** ``` seasons = ["Spring", "Summer", "Fall", "Winter"] for i in range(len(seasons)): # [consider-using-enumerate] print(i, seasons[i]) ``` **Correct code:** ``` seasons = ["Spring", "Summer", "Fall", "Winter"] for i, season in enumerate(seasons): print(i, season) ``` Created by the refactoring \ checker. ### consider-using-f-string / C0209 **Message emitted:** **Formatting a regular string which could be an f-string** **Description:** *Used when we detect a string that is being formatted with format() or % which could potentially be an f-string. The use of f-strings is preferred. Requires Python 3.6 and \`\`py-version \>= 3.6\`\`.* **Problematic code:** ``` from string import Template menu = ("eggs", "spam", 42.4) old_order = "%s and %s: %.2f ¤" % menu # [consider-using-f-string] beginner_order = menu[0] + " and " + menu[1] + ": " + str(menu[2]) + " ¤" joined_order = " and ".join(menu[:2]) # +1: [consider-using-f-string] format_order = "{} and {}: {:0.2f} ¤".format(menu[0], menu[1], menu[2]) # +1: [consider-using-f-string] named_format_order = "{eggs} and {spam}: {price:0.2f} ¤".format( eggs=menu[0], spam=menu[1], price=menu[2] ) template_order = Template("$eggs and $spam: $price ¤").substitute( eggs=menu[0], spam=menu[1], price=menu[2] ) ``` **Correct code:** ``` menu = ("eggs", "spam", 42.4) f_string_order = f"{menu[0]} and {menu[1]}: {menu[2]:0.2f} ¤" ``` **Additional details:** Formatted string literals (f-strings) give a concise, consistent syntax that can replace most use cases for the **%** formatting operator, **str.format()** and **string.Template**. F-strings also perform better than alternatives; see this tweet \ for a simple example. Created by the refactoring \ checker. ### dict-init-mutate / C3401 **Message emitted:** **Declare all known key/values when initializing the dictionary.** **Description:** *Dictionaries can be initialized with a single statement using dictionary literal syntax.* **Problematic code:** ``` fruit_prices = {} # [dict-init-mutate] fruit_prices["apple"] = 1 fruit_prices["banana"] = 10 ``` **Correct code:** ``` fruit_prices = {"apple": 1, "banana": 10} ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.dict_init_mutate, ``` **Note:** This message is emitted by the optional 'dict-init-mutate' \<#pylint-extensions-dict-init-mutate\> checker, which requires the **pylint.extensions.dict\_init\_mutate** plugin to be loaded. Created by the dict-init-mutate \ checker. ### disallowed-name / C0104 **Message emitted:** **Disallowed name "%s"** **Description:** *Used when the name matches bad-names or bad-names-rgxs- (unauthorized names).* **Problematic code:** ``` def foo(): # [disallowed-name] print("apples") ``` **Correct code:** ``` def print_fruit(): print("apples") ``` **Configuration file:** ``` [MAIN] bad-names=foo,bar,baz ``` Created by the basic \ checker. ### docstring-first-line-empty / C0199 **Message emitted:** **First line empty in %s docstring** **Description:** *Used when a blank line is found at the beginning of a docstring.* **Problematic code:** ``` def foo(): # [docstring-first-line-empty] """ Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book """ ``` **Correct code:** ``` def foo(): """Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book """ ``` **Configuration file:** ``` [MAIN] load-plugins = pylint.extensions.docstyle ``` **Note:** This message is emitted by the optional 'docstyle' \<#pylint-extensions-docstyle\> checker, which requires the **pylint.extensions.docstyle** plugin to be loaded. Created by the docstyle \ checker. ### import-outside-toplevel / C0415 **Message emitted:** **Import outside toplevel (%s)** **Description:** *Used when an import statement is used anywhere other than the module toplevel. Move this import to the top of the file.* **Problematic code:** ``` def print_python_version(): import sys # [import-outside-toplevel] print(sys.version_info) ``` **Correct code:** ``` import sys def print_python_version(): print(sys.version_info) ``` Created by the imports \ checker. ### import-private-name / C2701 **Message emitted:** **Imported private %s (%s)** **Description:** *Used when a private module or object prefixed with \_ is imported. PEP8 guidance on Naming Conventions states that public attributes with leading underscores should be considered private.* **Problematic code:** ``` from argparse import _AttributeHolder, _SubParsersAction # [import-private-name] attr_holder = _AttributeHolder() def add_sub_parser(sub_parsers: _SubParsersAction): sub_parsers.add_parser("my_subparser") # ... ``` **Correct code:** ``` """Private import can be used as type annotations.""" from argparse import _SubParsersAction def add_sub_parser(sub_parsers: _SubParsersAction): sub_parsers.add_parser("my_subparser") # ... ``` **Configuration file:** ``` [main] load-plugins = pylint.extensions.private_import ``` **Additional details:** Using private imports expose you to unexpected breaking changes for any version bump of your dependencies, even in patch versions. **Note:** This message is emitted by the optional 'import-private-name' \<#pylint-extensions-private-import\> checker, which requires the **pylint.extensions.private\_import** plugin to be loaded. Created by the import-private-name \ checker. ### invalid-characters-in-docstring / C0403 **Message emitted:** **Invalid characters %r in a docstring** **Description:** *Used when a word in docstring cannot be checked by enchant.* **Additional details:** This is a message linked to an internal problem in enchant. There's nothing to change in your code, but maybe in pylint's configuration or the way you installed the 'enchant' system library. Created by the spelling \ checker. ### invalid-name / C0103 **Message emitted:** **%s name "%s" doesn't conform to %s** **Description:** *Used when the name doesn't conform to naming rules associated to its type (constant, variable, class...).* **Problematic code:** ``` class cat: # [invalid-name] def Meow(self, NUMBER_OF_MEOW): # [invalid-name, invalid-name] print("Meow" * NUMBER_OF_MEOW) return NUMBER_OF_MEOW Cat = cat().Meow(42) # [invalid-name] ``` **Correct code:** ``` class Cat: def meow(self, number_of_meow): print("Meow" * number_of_meow) return number_of_meow CAT = Cat().meow(42) ``` **Additional details:** Pylint recognizes a number of different name types internally. With a few exceptions, the type of the name is governed by the location the assignment to a name is found in, and not the type of object assigned. | | | | --- | --- | | Name Type | Description | | **module** | Module and package names, same as the file names. | | **const** | Module-level constants: any name defined at module level that is not bound to a class object nor reassigned. | | **class** | Names in **class** statements, as well as names bound to class objects at module level. | | **function** | Functions, toplevel or nested in functions or methods. | | **method** | Methods, functions defined in class bodies. Includes static and class methods. | | **attr** | Attributes created on class instances inside methods. | | **argument** | Arguments to any function type, including lambdas. | | **variable** | Local variables in function scopes or module-level names that are assigned multiple times. | | **class-attribute** | Attributes defined in class bodies. | | **class-const** | Enum constants and class variables annotated with **Final** | | **inlinevar** | Loop variables in list comprehensions and generator expressions. | | **typevar** | Type variable declared with **TypeVar**. | | **paramspec** | Parameter specification variable declared with **ParamSpec**. | | **typevartuple** | Type variable tuple declared with **TypeVarTuple**. | | **typealias** | Type alias declared with **TypeAlias** or assignments of **Union**. | ### Default behavior By default, Pylint will enforce PEP8 \-suggested names. ### Predefined Naming Styles Pylint provides set of predefined naming styles. Those predefined naming styles may be used to adjust Pylint configuration to coding style used in linted project. Following predefined naming styles are available: - • **snake\_case** - • **camelCase** - • **PascalCase** - • **UPPER\_CASE** - • **any** - fake style which does not enforce any limitations The following options are exposed: - **--module-naming-style=\** - **--const-naming-style=\** - **--class-naming-style=\** - **--function-naming-style=\** - **--method-naming-style=\** - **--attr-naming-style=\** - **--argument-naming-style=\** - **--variable-naming-style=\** - **--class-attribute-naming-style=\** - **--class-const-naming-style=\** - **--inlinevar-naming-style=\** ### Predefined Naming Patterns Pylint provides predefined naming patterns for some names. These patterns are often based on a Naming Style but there is no option to choose one of the styles mentioned above. The pattern can be overwritten with the options discussed below. The following types of names are checked with a predefined pattern: | | | | | --- | --- | --- | | Name type | Good names | Bad names | | **typevar** | **T**, **\_CallableT**, **\_T\_co**, **AnyStr**, **DeviceTypeT**, **IPAddressT** | **DICT\_T**, **CALLABLE\_T**, **ENUM\_T**, **DeviceType**, **\_StrType** | | **paramspec** | **P**, **\_P** | **CALLABLE\_P** | | **typevartuple** | **Ts**, **\_Ts** | **TUPLE\_TS** | | **typealias** | **GoodName, \_GoodName, IPAddressType,** **GoodName2** and other PascalCase variants that don't start with **T** or **Type**. This is to distinguish them from **typevars**. Note that **TopName** is allowed but **TTopName** isn't. | **BadNameT, badName, TBadName, TypeBadName,** **\_1BadName** | Before pylint 3.0, most predefined patterns also enforced a minimum length of three characters. If this behavior is desired in versions 3.0 and following, it can be had by providing custom regular expressions as described next. (Or, if the **disallowed-name** check is sufficient instead of **invalid-name**, providing the single option **bad-names-rgxs="^..?$"** will suffice to fail 1-2 character names. ### Custom regular expressions If predefined naming styles are too limited, checker behavior may be further customized. For each name type, a separate regular expression matching valid names of this type can be defined. If any of custom regular expressions are defined, it overrides **\*-naming-style** option value. Regular expressions for the names are anchored at the beginning, any anchor for the end must be supplied explicitly. Any name not matching the regular expression will lead to an instance of **invalid-name**. - **--module-rgx=\** - **--const-rgx=\** - **--class-rgx=\** - **--function-rgx=\** - **--method-rgx=\** - **--attr-rgx=\** - **--argument-rgx=\** - **--variable-rgx=\** - **--class-attribute-rgx=\** - **--class-const-rgx=\** - **--inlinevar-rgx=\** - **--typevar-rgx=\** - **--paramspec-rgx=\** - **--typevartuple-rgx=\** - **--typealias-rgx=\** ### Multiple naming styles for custom regular expressions Large code bases that have been worked on for multiple years often exhibit an evolution in style as well. In some cases, modules can be in the same package, but still have different naming style based on the stratum they belong to. However, intra-module consistency should still be required, to make changes inside a single file easier. For this case, Pylint supports regular expression with several named capturing group. Rather than emitting name warnings immediately, Pylint will determine the prevalent naming style inside each module and enforce it on all names. Consider the following (simplified) example: ``` pylint --function-rgx='(?:(?P[a-z_]+)|(?P[a-z]+([A-Z][a-z]*)*))$' sample.py ``` The regular expression defines two naming styles, **snake** for snake-case names, and **camel** for camel-case names. In **sample.py**, the function name on line 1 and 7 will mark the module and enforce the match of named group **snake** for the remaining names in the module: ``` def valid_snake_case(arg): ... def InvalidCamelCase(arg): ... def more_valid_snake_case(arg): ... ``` Because of this, the name on line 4 will trigger an **invalid-name** warning, even though the name matches the given regex. Matches named **exempt** or **ignore** can be used for non-tainting names, to prevent built-in or interface-dictated names to trigger certain naming styles. - **--name-group=\** Default value: empty Format: comma-separated groups of colon-separated names. This option can be used to combine name styles. For example, **function:method** enforces that functions and methods use the same style, and a style triggered by either name type carries over to the other. This requires that the regular expression for the combined name types use the same group names. ### Name Hints - **--include-naming-hint=y\|n** Default: off Include a hint (regular expression used) for the correct name format with every **invalid-name** warning. Created by the basic \ checker. ### line-too-long / C0301 **Message emitted:** **Line too long (%s/%s)** **Description:** *Used when a line is longer than a given number of characters.* **Problematic code:** ``` # +1: [line-too-long] FRUIT = ["apricot", "blackcurrant", "cantaloupe", "dragon fruit", "elderberry", "fig", "grapefruit", ] ``` **Correct code:** ``` FRUIT = [ "apricot", "blackcurrant", "cantaloupe", "dragon fruit", "elderberry", "fig", "grapefruit", ] ``` **Configuration file:** ``` [MAIN] max-line-length=100 ``` **Additional details:** Pragma controls such as **# pylint: disable=all** are not counted toward line length for the purposes of this message. If you attempt to disable this message via **# pylint: disable=line-too-long** in a module with no code, you may receive a message for **useless-suppression**. This is a false positive of **useless-suppression** we can't easily fix. See \ for more information. Created by the format \ checker. ### misplaced-comparison-constant / C2201 **Message emitted:** **Comparison should be %s** **Description:** *Used when the constant is placed on the left side of a comparison. It is usually clearer in intent to place it in the right hand side of the comparison.* **Problematic code:** ``` def compare_apples(apples=20): for i in range(10): if 5 <= i: # [misplaced-comparison-constant] pass if 1 == i: # [misplaced-comparison-constant] pass if 20 < len(apples): # [misplaced-comparison-constant] pass ``` **Correct code:** ``` def compare_apples(apples=20): for i in range(10): if i >= 5: pass if i == 1: pass if len(apples) > 20: pass ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.comparison_placement ``` **Note:** This message is emitted by the optional 'comparison-placement' \<#pylint-extensions-comparison-placement\> checker, which requires the **pylint.extensions.comparison\_placement** plugin to be loaded. Created by the comparison-placement \ checker. ### missing-class-docstring / C0115 **Message emitted:** **Missing class docstring** **Description:** *Used when a class has no docstring. Even an empty class must have a docstring.* **Problematic code:** ``` class Person: # [missing-class-docstring] def __init__(self, first_name, last_name): self.first_name = first_name self.last_name = last_name ``` **Correct code:** ``` class Person: """Class representing a person""" def __init__(self, first_name, last_name): self.first_name = first_name self.last_name = last_name ``` Created by the basic \ checker. ### missing-final-newline / C0304 **Message emitted:** **Final newline missing** **Description:** *Used when the last line in a file is missing a newline.* **Problematic code:** **crlf.py**: ``` print("Hello") # CRLF (\r\n) print("world") # End-of-file (EOF) # [missing-final-newline] ``` **lf.py**: ``` print("Hello") # LF (\n) print("world") # End-of-file (EOF) # [missing-final-newline] ``` **Correct code:** **crlf.py**: ``` print("Hello") # CRLF (\r\n) print("world") # CRLF (\r\n) # End-of-file (EOF) ``` **lf.py**: ``` print("Hello") # LF (\n) print("world") # LF (\n) # End-of-file (EOF) ``` **Additional details:** - **The POSIX standard defines a line as:** "A sequence of zero or more non- \ characters plus a terminating \ character." **Related links:** - • POSIX Standard \ - • POSIX Standard Chapter 3.206 Line \ Created by the format \ checker. ### missing-function-docstring / C0116 **Message emitted:** **Missing function or method docstring** **Description:** *Used when a function or method has no docstring. Some special methods like \_\_init\_\_ do not require a docstring.* **Problematic code:** ``` import sys def print_python_version(): # [missing-function-docstring] print(sys.version) ``` **Correct code:** ``` import sys def print_python_version(): """Function printing python version.""" print(sys.version) ``` Created by the basic \ checker. ### missing-module-docstring / C0114 **Message emitted:** **Missing module docstring** **Description:** *Used when a module has no docstring. Empty modules do not require a docstring.* **Problematic code:** ``` import sys # [missing-module-docstring] def print_python_version(): print(sys.version) ``` **Correct code:** ``` """Module providing a function printing python version.""" import sys def print_python_version(): print(sys.version) ``` Created by the basic \ checker. ### mixed-line-endings / C0327 **Message emitted:** **Mixed line endings LF and CRLF** **Description:** *Used when there are mixed (LF and CRLF) newline signs in a file.* **Problematic code:** ``` print("Hello") # CRLF (\r\n) print("World") # LF (\n) # [mixed-line-endings] ``` **Correct code:** **full\_crlf.py**: ``` print("Hello") # CRLF (\r\n) print("World") # CRLF (\r\n) ``` **full\_lf.py**: ``` print("Hello") # LF (\n) print("World") # LF (\n) ``` **Related links:** - • History of CRLF and LF \ - • Dealing with line endings in Git \ - • A Collection of Useful .gitattributes Templates \ Created by the format \ checker. ### multiple-imports / C0410 **Message emitted:** **Multiple imports on one line (%s)** **Description:** *Used when import statement importing multiple modules is detected.* **Problematic code:** ``` import os, sys # [multiple-imports] ``` **Correct code:** ``` import os import sys ``` Created by the imports \ checker. ### multiple-statements / C0321 **Message emitted:** **More than one statement on a single line** **Description:** *Used when more than on statement are found on the same line.* **Problematic code:** ``` fruits = ["apple", "orange", "mango"] if "apple" in fruits: pass # [multiple-statements] else: print("no apples!") ``` **Correct code:** ``` fruits = ["apple", "orange", "mango"] if "apple" in fruits: pass else: print("no apples!") ``` Created by the format \ checker. ### non-ascii-module-import / C2403 **Message emitted:** **%s name "%s" contains a non-ASCII character, use an ASCII-only alias for import.** **Description:** *Used when the name contains at least one non-ASCII unicode character. See https://peps.python.org/pep-0672/#confusing-features for a background why this could be bad.* *If your programming guideline defines that you are programming in English, then there should be no need for non ASCII characters in Python Names. If not you can simply disable this check.* **Problematic code:** ``` from os.path import join as łos # [non-ascii-module-import] foo = łos("a", "b") ``` **Correct code:** ``` from os.path import join as os_join foo = os_join("a", "b") ``` Created by the nonascii-checker \ checker. ### non-ascii-name / C2401 **Message emitted:** **%s name "%s" contains a non-ASCII character, consider renaming it.** **Description:** *Used when the name contains at least one non-ASCII unicode character. See https://peps.python.org/pep-0672/#confusing-features for a background why this could be bad.* *If your programming guideline defines that you are programming in English, then there should be no need for non ASCII characters in Python Names. If not you can simply disable this check.* **Problematic code:** ``` ápple_count = 4444 # [non-ascii-name] ``` **Correct code:** ``` apple_count = 4444 ``` Created by the nonascii-checker \ checker. ### single-string-used-for-slots / C0205 **Message emitted:** **Class \_\_slots\_\_ should be a non-string iterable** **Description:** *Used when a class \_\_slots\_\_ is a simple string, rather than an iterable.* **Problematic code:** ``` class Fruit: # [single-string-used-for-slots] __slots__ = "name" def __init__(self, name): self.name = name ``` **Correct code:** ``` class Fruit: __slots__ = ("name",) def __init__(self, name): self.name = name ``` Created by the classes \ checker. ### singleton-comparison / C0121 **Message emitted:** **Comparison %s should be %s** **Description:** *Used when an expression is compared to singleton values like True, False or None.* **Problematic code:** ``` game_won = True if game_won == True: # [singleton-comparison] print("Game won !") ``` **Correct code:** ``` game_won = True if game_won: print("Game won !") ``` **Related links:** - • PEP 285 – Adding a bool type \ Created by the basic \ checker. ### superfluous-parens / C0325 **Message emitted:** **Unnecessary parens after %r keyword** **Description:** *Used when a single item in parentheses follows an if, for, or other keyword.* **Problematic code:** **example\_1.py**: ``` x = input() y = input() if (x == y): # [superfluous-parens] pass ``` **example\_2.py**: ``` i = 0 exclude = [] if (i - 0) in exclude: # [superfluous-parens] pass ``` **Correct code:** **example\_1.py**: ``` x = input() y = input() if x == y: pass ``` **example\_2.py**: ``` i = 0 exclude = [] if i - 0 in exclude: pass ``` Created by the format \ checker. ### too-many-lines / C0302 **Message emitted:** **Too many lines in module (%s/%s)** **Description:** *Used when a module has too many lines, reducing its readability.* **Problematic code:** ``` def is_palindrome(string): # [too-many-lines] left_pos = 0 right_pos = len(string) - 1 while right_pos >= left_pos: if not string[left_pos] == string[right_pos]: return False left_pos += 1 right_pos -= 1 return True def main(): print(is_palindrome("aza")) print(is_palindrome("racecar")) print(is_palindrome("trigger")) print(is_palindrome("ogre")) ``` **Correct code:** **\_\_init\_\_.py**: ``` __all__ = ["is_palindrome", "main"] from is_palindrome import is_palindrome from main import main ``` **is\_palindrome.py**: ``` def is_palindrome(string): return string == string[::-1] ``` **main.py**: ``` from is_palindrome import is_palindrome def main(): for string in ["aza", "racecar", "trigger", "ogre"]: print(is_palindrome(string)) ``` **Configuration file:** ``` [main] max-module-lines=15 ``` **Additional details:** When a module has too many lines it can make it difficult to read and understand. There might be performance issue while editing the file because the IDE must parse more code. You need more expertise to navigate the file properly (go to a particular line when debugging, or search for a specific code construct, instead of navigating by clicking and scrolling) This measure is a proxy for higher cyclomatic complexity that you might not be calculating if you're not using **load-plugins=pylint.extensions.mccabe,**. Cyclomatic complexity is slower to compute, but also a more fine grained measure than raw SLOC. In particular, you can't make the code less readable by making a very complex one liner if you're using cyclomatic complexity. The example simplify the code, but it's not always possible. Most of the time bursting the file by creating a package with the same API is the only solution. Anticipating and creating the file from the get go will permit to have the same end result with a better version control history. Created by the format \ checker. ### trailing-newlines / C0305 **Message emitted:** **Trailing newlines** **Description:** *Used when there are trailing blank lines in a file.* **Problematic code:** ``` print("apple") # The file ends with 2 lines that are empty # +1: [trailing-newlines] ``` **Correct code:** ``` print("apple") ``` Created by the format \ checker. ### trailing-whitespace / C0303 **Message emitted:** **Trailing whitespace** **Description:** *Used when there is whitespace between the end of a line and the newline.* **Problematic code:** ``` print("Hello") # [trailing-whitespace] # ^^^ trailing whitespaces ``` **Correct code:** ``` print("Hello") ``` Created by the format \ checker. ### typevar-double-variance / C0131 **Message emitted:** **TypeVar cannot be both covariant and contravariant** **Description:** *Emitted when both the "covariant" and "contravariant" keyword arguments are set to "True" in a TypeVar.* **Problematic code:** ``` from typing import TypeVar T = TypeVar("T", covariant=True, contravariant=True) # [typevar-double-variance] ``` **Correct code:** ``` from typing import TypeVar T_co = TypeVar("T_co", covariant=True) T_contra = TypeVar("T_contra", contravariant=True) ``` Created by the basic \ checker. ### typevar-name-incorrect-variance / C0105 **Message emitted:** **Type variable name does not reflect variance%s** **Description:** *Emitted when a TypeVar name doesn't reflect its type variance. According to PEP8, it is recommended to add suffixes '\_co' and '\_contra' to the variables used to declare covariant or contravariant behaviour respectively. Invariant (default) variables do not require a suffix. The message is also emitted when invariant variables do have a suffix.* **Problematic code:** ``` from typing import TypeVar T_co = TypeVar("T_co") # [typevar-name-incorrect-variance] ``` **Correct code:** ``` from typing import TypeVar T = TypeVar("T") ``` **Additional details:** When naming type vars, only use a **\_co** suffix when indicating covariance or **\_contra** when indicating contravariance. Created by the basic \ checker. ### typevar-name-mismatch / C0132 **Message emitted:** **TypeVar name "%s" does not match assigned variable name "%s"** **Description:** *Emitted when a TypeVar is assigned to a variable that does not match its name argument.* **Problematic code:** ``` from typing import TypeVar X = TypeVar("T") # [typevar-name-mismatch] ``` **Correct code:** ``` from typing import TypeVar T = TypeVar("T") ``` Created by the basic \ checker. ### unexpected-line-ending-format / C0328 **Message emitted:** **Unexpected line ending format. There is '%s' while it should be '%s'.** **Description:** *Used when there is different newline than expected.* **Problematic code:** ``` print("I'm drinking tea!") # CRLF (\r\n) # [unexpected-line-ending-format] print("I'm drinking water!") # CRLF (\r\n) # [unexpected-line-ending-format] ``` **Correct code:** ``` print("I'm drinking tea!") # LF (\n) print("I'm drinking water!") # LF (\n) ``` **Configuration file:** ``` [FORMAT] expected-line-ending-format=LF ``` **Related links:** - • History of CRLF and LF \ - • Dealing with line endings in Git \ - • A Collection of Useful .gitattributes Templates \ Created by the format \ checker. ### ungrouped-imports / C0412 **Message emitted:** **Imports from package %s are not grouped** **Description:** *Used when imports are not grouped by packages.* **Problematic code:** ``` import logging import os import sys import logging.config # [ungrouped-imports] from logging.handlers import WatchedFileHandler ``` **Correct code:** ``` import logging import logging.config import os import sys from logging.handlers import FileHandler ``` Created by the imports \ checker. ### unnecessary-direct-lambda-call / C3002 **Message emitted:** **Lambda expression called directly. Execute the expression inline instead.** **Description:** *Used when a lambda expression is directly called rather than executing its contents inline.* **Problematic code:** ``` y = (lambda x: x**2 + 2 * x + 1)(a) # [unnecessary-direct-lambda-call] ``` **Correct code:** ``` y = a**2 + 2 * a + 1 ``` Created by the lambda-expressions \ checker. ### unnecessary-dunder-call / C2801 **Message emitted:** **Unnecessarily calls dunder method %s. %s.** **Description:** *Used when a dunder method is manually called instead of using the corresponding function/method/operator.* **Problematic code:** ``` three = (3.0).__str__() # [unnecessary-dunder-call] twelve = "1".__add__("2") # [unnecessary-dunder-call] def is_bigger_than_two(x): return x.__gt__(2) # [unnecessary-dunder-call] ``` **Correct code:** ``` three = str(3.0) twelve = "1" + "2" def is_bigger_than_two(x): return x > 2 ``` **Related links:** - • Define dunder methods but don't call them directly \ Created by the unnecessary-dunder-call \ checker. ### unnecessary-lambda-assignment / C3001 **Message emitted:** **Lambda expression assigned to a variable. Define a function using the "def" keyword instead.** **Description:** *Used when a lambda expression is assigned to variable rather than defining a standard function with the "def" keyword.* **Problematic code:** ``` foo = lambda x: x**2 + 2 * x + 1 # [unnecessary-lambda-assignment] ``` **Correct code:** ``` def foo(x): return x**2 + 2 * x + 1 ``` Created by the lambda-expressions \ checker. ### unnecessary-negation / C0117 **Message emitted:** **Consider changing "%s" to "%s"** **Description:** *Used when a boolean expression contains an unneeded negation, e.g. when two negation operators cancel each other out.* **Problematic code:** **double\_not.py**: ``` if not not input(): # [unnecessary-negation] pass ``` **equivalent\_comparator\_exists.py**: ``` a = 3 b = 10 if not a > b: # [unnecessary-negation] pass ``` **Correct code:** **double\_not.py**: ``` if input(): pass ``` **equivalent\_comparator\_exists.py**: ``` a = 3 b = 10 if a <= b: pass ``` Created by the refactoring \ checker. ### use-implicit-booleaness-not-comparison / C1803 **Message emitted:** **"%s" can be simplified to "%s", if it is strictly a sequence, as an empty %s is falsey** **Description:** *Empty sequences are considered false in a boolean context. Following this check blindly in weakly typed code base can create hard to debug issues. If the value can be something else that is falsey but not a sequence (for example \`\`None\`\`, an empty string, or \`\`0\`\`) the code will not be equivalent.* **Problematic code:** ``` z = [] if z != []: # [use-implicit-booleaness-not-comparison] print("z is not an empty sequence") ``` **Correct code:** ``` z = [] if z: print("z is not an empty sequence") ``` Created by the refactoring \ checker. ### use-implicit-booleaness-not-comparison-to-string / C1804 **Message emitted:** **"%s" can be simplified to "%s", if it is strictly a string, as an empty string is falsey** **Description:** *Empty string are considered false in a boolean context. Following this check blindly in weakly typed code base can create hard to debug issues. If the value can be something else that is falsey but not a string (for example \`\`None\`\`, an empty sequence, or \`\`0\`\`) the code will not be equivalent.* **Caution:** This message is disabled by default. To enable it, add **use-implicit-booleaness-not-comparison-to-string** to the **enable** option. **Problematic code:** ``` def important_string_manipulation(x: str, y: str) -> None: if x == "": # [use-implicit-booleaness-not-comparison-to-string] print("x is an empty string") if y != "": # [use-implicit-booleaness-not-comparison-to-string] print("y is not an empty string") ``` **Correct code:** ``` def important_string_manipulation(x: str, y: str) -> None: if not x: print("x is an empty string") if y: print("y is not an empty string") ``` **Configuration file:** ``` [main] enable=use-implicit-booleaness-not-comparison-to-string ``` Created by the refactoring \ checker. ### use-implicit-booleaness-not-comparison-to-zero / C1805 **Message emitted:** **"%s" can be simplified to "%s", if it is strictly an int, as 0 is falsey** **Description:** *0 is considered false in a boolean context. Following this check blindly in weakly typed code base can create hard to debug issues. If the value can be something else that is falsey but not an int (for example \`\`None\`\`, an empty string, or an empty sequence) the code will not be equivalent.* **Caution:** This message is disabled by default. To enable it, add **use-implicit-booleaness-not-comparison-to-zero** to the **enable** option. **Problematic code:** ``` def important_math(x: int, y: int) -> None: if x == 0: # [use-implicit-booleaness-not-comparison-to-zero] print("x is equal to zero") if y != 0: # [use-implicit-booleaness-not-comparison-to-zero] print("y is not equal to zero") ``` **Correct code:** ``` def important_math(x: int, y: int) -> None: if not x: print("x is equal to zero") if y: print("y is not equal to zero") ``` **Configuration file:** ``` [main] enable=use-implicit-booleaness-not-comparison-to-zero ``` Created by the refactoring \ checker. ### use-implicit-booleaness-not-len / C1802 **Message emitted:** **Do not use \`len(SEQUENCE)\` without comparison to determine if a sequence is empty** **Description:** *Empty sequences are considered false in a boolean context. You can either remove the call to 'len' (\`\`if not x\`\`) or compare the length against a scalar (\`\`if len(x) \> 1\`\`).* **Problematic code:** ``` fruits = ["orange", "apple"] if len(fruits): # [use-implicit-booleaness-not-len] print(fruits) ``` **Correct code:** ``` fruits = ["orange", "apple"] if fruits: print(fruits) ``` Created by the refactoring \ checker. ### use-maxsplit-arg / C0207 **Message emitted:** **Use %s instead** **Description:** *Emitted when accessing only the first or last element of str.split(). The first and last element can be accessed by using str.split(sep, maxsplit=1)\[0\] or str.rsplit(sep, maxsplit=1)\[-1\] instead.* **Problematic code:** ``` url = "www.example.com" suffix = url.split(".")[-1] # [use-maxsplit-arg] ``` **Correct code:** ``` url = "www.example.com" suffix = url.rsplit(".", maxsplit=1)[-1] ``` **Additional details:** Be aware that the performance improvement from not splitting the string so many times will only be realized in cases presenting more instances of the splitting character than the minimal example here. Created by the refactoring \ checker. ### use-sequence-for-iteration / C0208 **Message emitted:** **Use a sequence type when iterating over values** **Description:** *When iterating over values, sequence types (e.g., \`\`lists\`\`, \`\`tuples\`\`, \`\`ranges\`\`) are more efficient than \`\`sets\`\`.* **Problematic code:** ``` for food in {"apples", "lemons", "water"}: # [use-sequence-for-iteration] print(f"I like {food}.") ``` **Correct code:** **list.py**: ``` for food in ["apples", "lemons", "water"]: print(f"I like {food}.") ``` **tuple.py**: ``` for food in ("apples", "lemons", "water"): print(f"I like {food}.") ``` **Additional details:** \ This example script shows a significant increase in performance when using a list, tuple or range over a set in python version 3.11.1. Created by the refactoring \ checker. ### useless-import-alias / C0414 **Message emitted:** **Import alias does not rename original package** **Description:** *Used when an import alias is same as original package, e.g., using import numpy as numpy instead of import numpy as np.* **Problematic code:** ``` import pandas as pandas # [useless-import-alias] ``` **Correct code:** ``` import pandas as pd ``` **Additional details:** ### Known issue If you prefer to use "from-as" to explicitly reexport in API (**from fruit import orange as orange**) instead of using **\_\_all\_\_** this message will be a false positive. Use **--allow-reexport-from-package** to allow explicit reexports by alias in package **\_\_init\_\_** files. **Related links:** - • \--allow-reexport-from-package \<#imports-options\> - • PEP 8, Import Guideline \ - • Pylint block-disable \<#block-disables\> - • mypy --no-implicit-reexport \ Created by the imports \ checker. ### wrong-import-order / C0411 **Message emitted:** **%s should be placed before %s** **Description:** *Used when PEP8 import order is not respected (standard imports first, then third-party libraries, then local imports).* **Problematic code:** ``` import os from . import utils import pylint # [wrong-import-order] import sys # [wrong-import-order] ``` **Correct code:** ``` import os import sys import pylint from . import utils ``` Created by the imports \ checker. ### wrong-import-position / C0413 **Message emitted:** **Import "%s" should be placed at the top of the module** **Description:** *Used when code and imports are mixed.* **Problematic code:** ``` import os home = os.environ["HOME"] import sys # [wrong-import-position] print(f"Home directory is {home}", file=sys.stderr) ``` **Correct code:** ``` import os import sys home = os.environ["HOME"] print(f"Home directory is {home}", file=sys.stderr) ``` Created by the imports \ checker. ### wrong-spelling-in-comment / C0401 **Message emitted:** **Wrong spelling of a word '%s' in a comment:** **%s** **%s** **Did you mean: '%s'?** **Description:** *Used when a word in comment is not spelled correctly.* **Problematic code:** ``` # There's a mistkae in this string # [wrong-spelling-in-comment] ``` **Correct code:** ``` # There's no mistake in this string ``` **Configuration file:** ``` [main] # This might not run in your env if you don't have the en_US dict installed. spelling-dict=en_US ``` Created by the spelling \ checker. ### wrong-spelling-in-docstring / C0402 **Message emitted:** **Wrong spelling of a word '%s' in a docstring:** **%s** **%s** **Did you mean: '%s'?** **Description:** *Used when a word in docstring is not spelled correctly.* **Problematic code:** ``` """There's a mistkae in this string""" # [wrong-spelling-in-docstring] ``` **Correct code:** ``` """There's no mistake in this string""" ``` **Configuration file:** ``` [main] # This might not run in your env if you don't have the en_US dict installed. spelling-dict=en_US ``` Created by the spelling \ checker. All renamed messages in the convention category: ### blacklisted-name / C0102 'blacklisted-name' has been renamed. The new message can be found at: ### compare-to-empty-string / C1901 'compare-to-empty-string' has been renamed. The new message can be found at: ### compare-to-zero / C2001 'compare-to-zero' has been renamed. The new message can be found at: ### len-as-condition / C1801 'len-as-condition' has been renamed. The new message can be found at: ### missing-docstring / C0111 'missing-docstring' has been renamed. The new message can be found at: ### old-misplaced-comparison-constant / C0122 'old-misplaced-comparison-constant' has been renamed. The new message can be found at: ### old-non-ascii-name / C0144 'old-non-ascii-name' has been renamed. The new message can be found at: ### unneeded-not / C0113 'unneeded-not' has been renamed. The new message can be found at: ### Refactor All messages in the refactor category: ### chained-comparison / R1716 **Message emitted:** **Simplify chained comparison between the operands** **Description:** *This message is emitted when pylint encounters boolean operation like "a \< b and b \< c", suggesting instead to refactor it to "a \< b \< c"* **Problematic code:** ``` a = int(input()) b = int(input()) c = int(input()) if a < b and b < c: # [chained-comparison] pass ``` **Correct code:** ``` a = int(input()) b = int(input()) c = int(input()) if a < b < c: pass ``` Created by the refactoring \ checker. ### comparison-of-constants / R0133 **Message emitted:** **Comparison between constants: "%s %s %s" has a constant value** **Description:** *When two literals are compared with each other the result is a constant. Using the constant directly is both easier to read and more performant. Initializing 'True' and 'False' this way is not required since Python 2.3.* **Problematic code:** ``` def is_the_answer() -> bool: return 42 == 42 # [comparison-of-constants] ``` **Correct code:** ``` def is_the_answer(meaning_of_life: int) -> bool: return meaning_of_life == 42 ``` Created by the basic \ checker. ### comparison-with-itself / R0124 **Message emitted:** **Redundant comparison - %s** **Description:** *Used when something is compared against itself.* **Problematic code:** ``` def is_an_orange(fruit): an_orange = "orange" return fruit == fruit # [comparison-with-itself] ``` **Correct code:** ``` def is_an_orange(fruit): an_orange = "orange" return an_orange == fruit ``` Created by the basic \ checker. ### condition-evals-to-constant / R1727 **Message emitted:** **Boolean condition '%s' will always evaluate to '%s'** **Description:** *Emitted when a boolean condition can be simplified to a constant value.* **Problematic code:** ``` def is_a_fruit(fruit): return bool(fruit in {"apple", "orange"} or True) # [condition-evals-to-constant] ``` **Correct code:** ``` def is_a_fruit(fruit): return fruit in {"apple", "orange"} ``` Created by the refactoring \ checker. ### confusing-consecutive-elif / R5601 **Message emitted:** **Consecutive elif with differing indentation level, consider creating a function to separate the inner elif** **Description:** *Used when an elif statement follows right after an indented block which itself ends with if or elif. It may not be obvious if the elif statement was willingly or mistakenly unindented. Extracting the indented if statement into a separate function might avoid confusion and prevent errors.* **Problematic code:** ``` def myfunc(shall_continue: bool, shall_exit: bool): if shall_continue: if input("Are you sure?") == "y": print("Moving on.") elif shall_exit: # [confusing-consecutive-elif] print("Exiting.") ``` **Correct code:** ``` # Option 1: add explicit 'else' def myfunc(shall_continue: bool, shall_exit: bool): if shall_continue: if input("Are you sure?") == "y": print("Moving on.") else: pass elif shall_exit: print("Exiting.") # Option 2: extract function def user_confirmation(): if input("Are you sure?") == "y": print("Moving on.") def myfunc2(shall_continue: bool, shall_exit: bool): if shall_continue: user_confirmation() elif shall_exit: print("Exiting.") ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.confusing_elif ``` **Additional details:** Creating a function for the nested conditional, or adding an explicit **else** in the indented **if** statement, even if it only contains a **pass** statement, can help clarify the code. **Note:** This message is emitted by the optional 'confusing\_elif' \<#pylint-extensions-confusing-elif\> checker, which requires the **pylint.extensions.confusing\_elif** plugin to be loaded. Created by the confusing\_elif \ checker. ### consider-alternative-union-syntax / R6003 **Message emitted:** **Consider using alternative union syntax instead of '%s'%s** **Description:** *Emitted when \`\`typing.Union\`\` or \`\`typing.Optional\`\` is used instead of the shorthand union syntax. For example, \`\`Union\[int, float\]\`\` instead of \`\`int \| float\`\`. Using the shorthand for unions aligns with Python typing recommendations, removes the need for imports, and avoids confusion in function signatures.* **Problematic code:** ``` from typing import Optional, Union def forecast( temp: Union[int, float], # [consider-alternative-union-syntax] unit: Optional[str], # [consider-alternative-union-syntax] ) -> None: print(f'Temperature: {temp}{unit or ""}') ``` **Correct code:** ``` def forecast(temp: int | float, unit: str | None) -> None: print(f'Temperature: {temp}{unit or ""}') ``` **Configuration file:** ``` [MAIN] load-plugins = pylint.extensions.typing ``` **Additional details:** Using the shorthand syntax for union types is recommended over the **typing** module \. This is consistent with the broader recommendation to prefer built-in types over imports (for example, using **list** instead of the now-deprecated **typing.List**). **typing.Optional** can also cause confusion in annotated function arguments, since an argument annotated as **Optional** is still a *required* argument when a default value is not set. Explicitly annotating such arguments with **type \| None** makes the intention clear. **Note:** This message is emitted by the optional 'typing' \<#pylint-extensions-typing\> checker, which requires the **pylint.extensions.typing** plugin to be loaded. Created by the typing \ checker. ### consider-math-not-float / R6106 **Message emitted:** **Consider %smath.%s instead of %s** **Description:** *Using math.inf or math.nan permits to benefit from typing and it is up to 4 times faster than a float call (after the initial import of math). This check also catches typos in float calls as a side effect.* **Problematic code:** ``` swag = float("inf") # [consider-math-not-float] ``` **Correct code:** ``` import math swag = math.inf ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.code_style ``` **Additional details:** This is an extension check because the typing advantage could be fixed. Regarding performance, float("nan") and float("inf") are slower than their counterpart math.inf and math.nan by a factor of 4 after the initial import of math. ``` import math import timeit time_math_inf = timeit.timeit('math.nan', globals=globals(), number=10**8) print(f'math.nan: {time_math_inf:.2f} seconds') import timeit time_inf_str = timeit.timeit('float("nan")', number=10**8) print(f'float("nan"): {time_inf_str:.2f} seconds') ``` Result: ``` math.nan: 1.24 seconds float("nan"): 5.15 seconds ``` But if we take the initial import into account it's worse. ``` import timeit time_math_inf = timeit.timeit('import math;math.nan', globals=globals(), number=10**8) print(f'math.nan: {time_math_inf:.2f} seconds') import timeit time_inf_str = timeit.timeit('float("nan")', number=10**8) print(f'float("nan"): {time_inf_str:.2f} seconds') ``` Result: ``` math.nan: 9.08 seconds float("nan"): 5.33 seconds ``` So the decision depends on how and how often you need to use it and what matter to you. **Note:** This message is emitted by the optional 'code\_style' \<#pylint-extensions-code-style\> checker, which requires the **pylint.extensions.code\_style** plugin to be loaded. Created by the code\_style \ checker. ### consider-merging-isinstance / R1701 **Message emitted:** **Consider merging these isinstance calls to isinstance(%s, (%s))** **Description:** *Used when multiple consecutive isinstance calls can be merged into one.* **Problematic code:** ``` from typing import Any def is_number(value: Any) -> bool: # +1: [consider-merging-isinstance] return isinstance(value, int) or isinstance(value, float) ``` **Correct code:** ``` from typing import Any def is_number(value: Any) -> bool: return isinstance(value, (int, float)) ``` Created by the refactoring \ checker. ### consider-refactoring-into-while-condition / R3501 **Message emitted:** **Consider using 'while %s' instead of 'while %s:' an 'if', and a 'break'** **Description:** *Emitted when \`while True:\` loop is used and the first statement is a break condition. The \`\`if / break\`\` construct can be removed if the check is inverted and moved to the \`\`while\`\` statement.* **Problematic code:** ``` fruit_basket = ["apple", "orange", "banana", "cherry", "guava"] while True: # [consider-refactoring-into-while-condition] if len(fruit_basket) == 0: break fruit = fruit_basket.pop() print(f"We removed {fruit} from the basket") ``` **Correct code:** ``` fruit_basket = ["apple", "orange", "banana", "cherry", "guava"] while len(fruit_basket) != 0: fruit = fruit_basket.pop() print(f"We removed {fruit} from the basket") ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.consider_refactoring_into_while_condition ``` **Note:** This message is emitted by the optional 'consider\_refactoring\_into\_while' \<#pylint-extensions-consider-refactoring-into-while-condition\> checker, which requires the **pylint.extensions.consider\_refactoring\_into\_while\_condition** plugin to be loaded. Created by the consider\_refactoring\_into\_while \ checker. ### consider-swap-variables / R1712 **Message emitted:** **Consider using tuple unpacking for swapping variables** **Description:** *You do not have to use a temporary variable in order to swap variables. Using "tuple unpacking" to directly swap variables makes the intention more clear.* **Problematic code:** ``` a = 1 b = 2 temp = a # [consider-swap-variables] a = b b = temp ``` **Correct code:** ``` a = 1 b = 2 a, b = b, a ``` Created by the refactoring \ checker. ### consider-using-alias / R6002 **Message emitted:** **'%s' will be deprecated with PY39, consider using '%s' instead%s** **Description:** *Only emitted if 'runtime-typing=no' and a deprecated typing alias is used in a type annotation context in Python 3.7 or 3.8.* **Problematic code:** ``` import typing cats: typing.Dict[str, int] # [consider-using-alias] ``` **Correct code:** ``` import typing cats: typing.cast(dict[str, int], "string") ``` **Configuration file:** ``` [main] load-plugins = pylint.extensions.typing py-version = 3.7 runtime-typing=no ``` **Note:** This message is emitted by the optional 'typing' \<#pylint-extensions-typing\> checker, which requires the **pylint.extensions.typing** plugin to be loaded. Created by the typing \ checker. ### consider-using-assignment-expr / R6103 **Message emitted:** **Use '%s' instead** **Description:** *Emitted when an if assignment is directly followed by an if statement and both can be combined by using an assignment expression \`\`:=\`\`. Requires Python 3.8 and \`\`py-version \>= 3.8\`\`.* **Problematic code:** ``` apples = 2 if apples: # [consider-using-assignment-expr] print("God apples!") ``` **Correct code:** ``` if apples := 2: print("God apples!") ``` **Configuration file:** ``` [MAIN] py-version=3.8 load-plugins=pylint.extensions.code_style ``` **Note:** This message is emitted by the optional 'code\_style' \<#pylint-extensions-code-style\> checker, which requires the **pylint.extensions.code\_style** plugin to be loaded. Created by the code\_style \ checker. ### consider-using-augmented-assign / R6104 **Message emitted:** **Use '%s' to do an augmented assign directly** **Description:** *Emitted when an assignment is referring to the object that it is assigning to. This can be changed to be an augmented assign.* *Disabled by default!* **Caution:** This message is disabled by default. To enable it, add **consider-using-augmented-assign** to the **enable** option. **Problematic code:** ``` x = 1 x = x + 1 # [consider-using-augmented-assign] ``` **Correct code:** ``` x = 1 x += 1 ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.code_style enable=consider-using-augmented-assign ``` **Note:** This message is emitted by the optional 'code\_style' \<#pylint-extensions-code-style\> checker, which requires the **pylint.extensions.code\_style** plugin to be loaded. Created by the code\_style \ checker. ### consider-using-dict-comprehension / R1717 **Message emitted:** **Consider using a dictionary comprehension** **Description:** *Emitted when we detect the creation of a dictionary using the dict() callable and a transient list. Although there is nothing syntactically wrong with this code, it is hard to read and can be simplified to a dict comprehension. Also it is faster since you don't need to create another transient list* **Problematic code:** ``` NUMBERS = [1, 2, 3] # +1: [consider-using-dict-comprehension] DOUBLED_NUMBERS = dict([(number, number * 2) for number in NUMBERS]) ``` **Correct code:** ``` NUMBERS = [1, 2, 3] DOUBLED_NUMBERS = {number: number * 2 for number in NUMBERS} ``` **Additional details:** pyupgrade \ or ruff \ can fix this issue automatically. Created by the refactoring \ checker. ### consider-using-from-import / R0402 **Message emitted:** **Use 'from %s import %s' instead** **Description:** *Emitted when a submodule of a package is imported and aliased with the same name, e.g., instead of \`\`import concurrent.futures as futures\`\` use \`\`from concurrent import futures\`\`.* **Problematic code:** ``` import os.path as path # [consider-using-from-import] ``` **Correct code:** ``` from os import path ``` Created by the imports \ checker. ### consider-using-generator / R1728 **Message emitted:** **Consider using a generator instead '%s(%s)'** **Description:** *If your container can be large using a generator will bring better performance.* **Problematic code:** ``` list([0 for y in list(range(10))]) # [consider-using-generator] tuple([0 for y in list(range(10))]) # [consider-using-generator] sum([y**2 for y in list(range(10))]) # [consider-using-generator] max([y**2 for y in list(range(10))]) # [consider-using-generator] min([y**2 for y in list(range(10))]) # [consider-using-generator] ``` **Correct code:** ``` list(0 for y in list(range(10))) tuple(0 for y in list(range(10))) sum(y**2 for y in list(range(10))) max(y**2 for y in list(range(10))) min(y**2 for y in list(range(10))) ``` **Additional details:** Removing **\[\]** inside calls that can use containers or generators should be considered for performance reasons since a generator will have an upfront cost to pay. The performance will be better if you are working with long lists or sets. For **max**, **min** and **sum** using a generator is also recommended by pep289. **Related links:** - • PEP 289 \ - • Benchmark and discussion for any/all/list/tuple \ - • Benchmark and discussion for sum/max/min \ Created by the refactoring \ checker. ### consider-using-get / R1715 **Message emitted:** **Consider using dict.get for getting values from a dict if a key is present or a default if not** **Description:** *Using the builtin dict.get for getting a value from a dictionary if a key is present or a default if not, is simpler and considered more idiomatic, although sometimes a bit slower* **Problematic code:** ``` knights = {"Gallahad": "the pure", "Robin": "the brave"} if "Gallahad" in knights: # [consider-using-get] DESCRIPTION = knights["Gallahad"] else: DESCRIPTION = "" ``` **Correct code:** ``` knights = {"Gallahad": "the pure", "Robin": "the brave"} description = knights.get("Gallahad", "") ``` Created by the refactoring \ checker. ### consider-using-in / R1714 **Message emitted:** **Consider merging these comparisons with 'in' by using '%s %sin (%s)'. Use a set instead if elements are hashable.** **Description:** *To check if a variable is equal to one of many values, combine the values into a set or tuple and check if the variable is contained "in" it instead of checking for equality against each of the values. This is faster and less verbose.* **Problematic code:** ``` def fruit_is_round(fruit): # +1: [consider-using-in] return fruit == "apple" or fruit == "orange" or fruit == "melon" ``` **Correct code:** ``` def fruit_is_round(fruit): return fruit in {"apple", "orange", "melon"} ``` Created by the refactoring \ checker. ### consider-using-join / R1713 **Message emitted:** **Consider using str.join(sequence) for concatenating strings from an iterable** **Description:** *Using str.join(sequence) is faster, uses less memory and increases readability compared to for-loop iteration.* **Problematic code:** ``` def fruits_to_string(fruits): formatted_fruit = "" for fruit in fruits: formatted_fruit += fruit # [consider-using-join] return formatted_fruit print(fruits_to_string(["apple", "pear", "peach"])) ``` **Correct code:** ``` print("".join(["apple", "pear", "peach"])) ``` Created by the refactoring \ checker. ### consider-using-max-builtin / R1731 **Message emitted:** **Consider using '%s' instead of unnecessary if block** **Description:** *Using the max builtin instead of a conditional improves readability and conciseness.* **Problematic code:** ``` def get_max(value1, value2): if value1 < value2: # [consider-using-max-builtin] value1 = value2 return value1 print(get_max(1, 2)) ``` **Correct code:** ``` print(max(1, 2)) ``` Created by the refactoring \ checker. ### consider-using-min-builtin / R1730 **Message emitted:** **Consider using '%s' instead of unnecessary if block** **Description:** *Using the min builtin instead of a conditional improves readability and conciseness.* **Problematic code:** ``` def get_min(value1, value2): if value1 > value2: # [consider-using-min-builtin] value1 = value2 return value1 print(get_min(1, 2)) ``` **Correct code:** ``` print(min(1, 2)) ``` Created by the refactoring \ checker. ### consider-using-namedtuple-or-dataclass / R6101 **Message emitted:** **Consider using namedtuple or dataclass for dictionary values** **Description:** *Emitted when dictionary values can be replaced by namedtuples or dataclass instances.* **Problematic code:** ``` FELIDAES = { # [consider-using-namedtuple-or-dataclass] "The queen's cymric, fragile furry friend": { "tail_length_cm": 1, "paws": 4, "eyes": 2, "Elizabethan collar": 1, }, "Rackat the red, terror of the sea": { "tail_length_cm": 13, "paws": 3, "eyes": 1, "Red Hat": 1, }, } ``` **Correct code:** ``` from typing import NamedTuple class FelidaeCharacteristics(NamedTuple): tail_length_cm: int paws: int eyes: int hat: str | None FELIDAES = { "The queen's cymric, fragile furry friend": FelidaeCharacteristics( tail_length_cm=1, paws=4, eyes=2, hat="Elizabethan collar" ), "Rackat the red, terror of the sea": FelidaeCharacteristics( tail_length_cm=21, paws=3, eyes=1, hat="Red Hat" ), } ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.code_style ``` **Note:** This message is emitted by the optional 'code\_style' \<#pylint-extensions-code-style\> checker, which requires the **pylint.extensions.code\_style** plugin to be loaded. Created by the code\_style \ checker. ### consider-using-set-comprehension / R1718 **Message emitted:** **Consider using a set comprehension** **Description:** *Although there is nothing syntactically wrong with this code, it is hard to read and can be simplified to a set comprehension. Also it is faster since you don't need to create another transient list* **Problematic code:** ``` NUMBERS = [1, 2, 2, 3, 4, 4] # +1: [consider-using-set-comprehension] UNIQUE_EVEN_NUMBERS = set([number for number in NUMBERS if number % 2 == 0]) ``` **Correct code:** ``` NUMBERS = [1, 2, 2, 3, 4, 4] UNIQUE_EVEN_NUMBERS = {number for number in NUMBERS if number % 2 == 0} ``` **Additional details:** pyupgrade \ or ruff \ can fix this issue automatically. Created by the refactoring \ checker. ### consider-using-sys-exit / R1722 **Message emitted:** **Consider using 'sys.exit' instead** **Description:** *Contrary to 'exit()' or 'quit()', 'sys.exit' does not rely on the site module being available (as the 'sys' module is always available).* **Problematic code:** ``` if __name__ == "__main__": user = input("Enter user name: ") print(f"Hello, {user}") exit(0) # [consider-using-sys-exit] ``` **Correct code:** ``` import sys if __name__ == "__main__": user = input("Enter user name: ") print(f"Hello, {user}") sys.exit(0) ``` Created by the refactoring \ checker. ### consider-using-ternary / R1706 **Message emitted:** **Consider using ternary (%s)** **Description:** *Used when one of known pre-python 2.5 ternary syntax is used.* **Problematic code:** ``` x, y = 1, 2 maximum = x >= y and x or y # [consider-using-ternary] ``` **Correct code:** ``` x, y = 1, 2 maximum = x if x >= y else y ``` Created by the refactoring \ checker. ### consider-using-tuple / R6102 **Message emitted:** **Consider using an in-place tuple instead of list** **Description:** *Only for style consistency! Emitted where an in-place defined \`\`list\`\` can be replaced by a \`\`tuple\`\`. Due to optimizations by CPython, there is no performance benefit from it.* **Problematic code:** ``` for i in [1, 2, 3]: # [consider-using-tuple] print(i) ``` **Correct code:** ``` for i in (1, 2, 3): print(i) ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.code_style ``` **Note:** This message is emitted by the optional 'code\_style' \<#pylint-extensions-code-style\> checker, which requires the **pylint.extensions.code\_style** plugin to be loaded. Created by the code\_style \ checker. ### consider-using-with / R1732 **Message emitted:** **Consider using 'with' for resource-allocating operations** **Description:** *Emitted if a resource-allocating assignment or call may be replaced by a 'with' block. By using 'with' the release of the allocated resources is ensured even in the case of an exception.* **Problematic code:** **close.py**: ``` file = open("apple.txt", "r", encoding="utf8") # [consider-using-with] contents = file.read() file.close() ``` **not\_even\_close.py**: ``` contents = open("apple.txt", "r", encoding="utf8").read() # [consider-using-with] ``` **Correct code:** ``` with open("apple.txt", "r", encoding="utf8") as file: contents = file.read() ``` **Additional details:** Calling **write()** without using the **with** keyword or calling **close()** might result in the arguments of **write()** not being completely written to the disk, even if the program exits successfully. This message applies to callables of Python's stdlib which can be replaced by a **with** statement. It is suppressed in the following cases: - • the call is located inside a context manager - • the call result is returned from the enclosing function - • the call result is used in a **with** statement itself **Related links:** - • Python doc: Reading and writing files \ - • PEP 343 \ - • Context managers in Python \ by John Lekberg - • Rationale \ Created by the refactoring \ checker. ### cyclic-import / R0401 **Message emitted:** **Cyclic import (%s)** **Description:** *Used when a cyclic import between two or more modules is detected.* **Problematic code:** **\_\_init\_\_.py**: ``` ``` **bad.py**: ``` def count_to_one(): return 1 def count_to_three(): from .bad2 import count_to_two return count_to_two() + 1 ``` **bad2.py**: ``` from .bad import count_to_one # [cyclic-import] def count_to_two(): return count_to_one() + 1 ``` **Correct code:** ``` def count_to_one(): return 1 def count_to_two(): return count_to_one() + 1 def count_to_three(): return count_to_two() + 1 ``` **Additional details:** The good code is just an example. There are various strategies to resolving cyclic imports and the best choice relies heavily on the context of the code and the affected modules. Created by the imports \ checker. ### duplicate-code / R0801 **Message emitted:** **Similar lines in %s files** **%s** **Description:** *Indicates that a set of similar lines has been detected among multiple file. This usually means that the code should be refactored to avoid this duplication.* **Problematic code:** **\_\_init\_\_.py**: ``` ``` **apple.py**: ``` class Apple: def __init__(self): self.remaining_bites = 3 def take_bite(self): if self.remaining_bites > 0: print("You take a bite of the apple.") self.remaining_bites -= 1 else: print("The apple is already eaten up!") def eaten_by_animal(self, animal): self.remaining_bites = 0 print("The apple has been eaten by an animal.") ``` **orange.py**: ``` class Orange: # [duplicate-code] def __init__(self): self.remaining_bites = 3 def take_bite(self): if self.remaining_bites > 0: print("You take a bite of the apple.") self.remaining_bites -= 1 else: print("The orange is already eaten up!") def eaten_by_animal(self, animal): if animal == "cat": raise ValueError("A cat would never do that !") self.remaining_bites = 0 print("The orange has been eaten by an animal.") ``` **Correct code:** **\_\_init\_\_.py**: ``` ``` **apple.py**: ``` from fruit import Fruit class Apple(Fruit): ... ``` **fruit.py**: ``` class Fruit: def __init__(self): self.remaining_bites = 3 def take_bite(self): if self.remaining_bites > 0: print(f"You take a bite of the {self.__class__.__name__.lower()}.") self.remaining_bites -= 1 else: print(f"The {self.__class__.__name__.lower()} is already eaten up!") def eaten_by_animal(self, animal): self.remaining_bites = 0 print(f"The {self.__class__.__name__.lower()} has been eaten by an animal.") ``` **orange.py**: ``` from fruit import Fruit class Orange(Fruit): def eaten_by_animal(self, animal): if animal == "cat": raise ValueError("A cat would never do that !") super().eaten_by_animal(animal) ``` **Additional details:** If you need to make a change to the logic or functionality of the duplicated code, you will need to identify all the places that need to be changed, which can be time-consuming and error-prone. If there are multiple copies of the same code, then you will also need to test each copy to ensure that the functionality is correct. Duplicate code can be confusing for someone who is trying to understand the logic and flow of the code if they come across multiple identical or nearly identical blocks of code. The reader can then skim and think something is identical when it actually isn't. This is particularly true during review. Created by the similarities \ checker. ### else-if-used / R5501 **Message emitted:** **Consider using "elif" instead of "else" then "if" to remove one indentation level** **Description:** *Used when an else statement is immediately followed by an if statement and does not contain statements that would be unrelated to it.* **Problematic code:** ``` if input(): pass else: if len(input()) >= 10: # [else-if-used] pass else: pass ``` **Correct code:** ``` if input(): pass elif len(input()) >= 10: pass else: pass ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.check_elif ``` **Note:** This message is emitted by the optional 'else\_if\_used' \<#pylint-extensions-check-elif\> checker, which requires the **pylint.extensions.check\_elif** plugin to be loaded. Created by the else\_if\_used \ checker. ### empty-comment / R2044 **Message emitted:** **Line with empty comment** **Description:** *Used when a # symbol appears on a line not followed by an actual comment* **Problematic code:** ``` # +1:[empty-comment] # # +1:[empty-comment] x = 0 # ``` **Correct code:** ``` # comment x = 0 # comment ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.empty_comment ``` **Note:** This message is emitted by the optional 'empty-comment' \<#pylint-extensions-empty-comment\> checker, which requires the **pylint.extensions.empty\_comment** plugin to be loaded. Created by the empty-comment \ checker. ### inconsistent-return-statements / R1710 **Message emitted:** **Either all return statements in a function should return an expression, or none of them should.** **Description:** *According to PEP8, if any return statement returns an expression, any return statements where no value is returned should explicitly state this as return None, and an explicit return statement should be present at the end of the function (if reachable)* **Problematic code:** ``` def get_the_answer(value: str) -> str | None: # [inconsistent-return-statements] if value: return value ``` **Correct code:** ``` def get_the_answer(value: str) -> str | None: if value: return value return None ``` Created by the refactoring \ checker. ### literal-comparison / R0123 **Message emitted:** **In '%s', use '%s' when comparing constant literals not '%s' ('%s')** **Description:** *Used when comparing an object to a literal, which is usually what you do not want to do, since you can compare to a different literal than what was expected altogether.* **Problematic code:** ``` def is_an_orange(fruit): return fruit is "orange" # [literal-comparison] ``` **Correct code:** ``` def is_an_orange(fruit): return fruit == "orange" ``` **Related links:** - • Comparison operations in Python \ Created by the basic \ checker. ### magic-value-comparison / R2004 **Message emitted:** **Consider using a named constant or an enum instead of '%s'.** **Description:** *Using named constants instead of magic values helps improve readability and maintainability of your code, try to avoid them in comparisons.* **Problematic code:** ``` import random measurement = random.randint(0, 200) above_threshold = False i = 0 while i < 5: # [magic-value-comparison] above_threshold = measurement > 100 # [magic-value-comparison] if above_threshold: break measurement = random.randint(0, 200) ``` **Correct code:** ``` import random MAX_NUM_OF_ITERATIONS = 5 THRESHOLD_VAL = 100 MIN_MEASUREMENT_VAL = 0 MAX_MEASUREMENT_VAL = 200 measurement = random.randint(MIN_MEASUREMENT_VAL, MAX_MEASUREMENT_VAL) above_threshold = False i = 0 while i < MAX_NUM_OF_ITERATIONS: above_threshold = measurement > THRESHOLD_VAL if above_threshold: break measurement = random.randint(MIN_MEASUREMENT_VAL, MAX_MEASUREMENT_VAL) ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.magic_value ``` **Note:** This message is emitted by the optional 'magic-value' \<#pylint-extensions-magic-value\> checker, which requires the **pylint.extensions.magic\_value** plugin to be loaded. Created by the magic-value \ checker. ### match-class-bind-self / R1905 **Message emitted:** **Use '%s() as %s' instead** **Description:** *Match class patterns are faster if the name binding happens for the whole pattern and any lookup for \`\_\_match\_args\_\_\` can be avoided.* **Problematic code:** ``` class Book: __match_args__ = ("title", "year") def __init__(self, title, year): self.title = title self.year = year def func(item: Book): match item: case Book(title=str(title)): # [match-class-bind-self] ... case Book(year=int(year)): # [match-class-bind-self] ... ``` **Correct code:** ``` class Book: __match_args__ = ("title", "year") def __init__(self, title, year): self.title = title self.year = year def func(item: Book): match item: case Book(title=str() as title): ... case Book(year=int() as year): ... ``` **Related links:** - • Python documentation \ Created by the match\_statements \ checker. ### match-class-positional-attributes / R1906 **Message emitted:** **Use keyword attributes instead of positional ones (%s)** **Description:** *Keyword attributes are more explicit and slightly faster since CPython can skip the \`\_\_match\_args\_\_\` lookup.* **Problematic code:** ``` class Book: __match_args__ = ("title", "year") def __init__(self, title, year): self.title = title self.year = year def func(item: Book): match item: case Book("abc", 2000): # [match-class-positional-attributes] ... ``` **Correct code:** ``` class Book: __match_args__ = ("title", "year") def __init__(self, title, year): self.title = title self.year = year def func(item: Book): match item: case Book(title="abc", year=2000): ... ``` **Related links:** - • Python documentation \ Created by the match\_statements \ checker. ### no-classmethod-decorator / R0202 **Message emitted:** **Consider using a decorator instead of calling classmethod** **Description:** *Used when a class method is defined without using the decorator syntax.* **Problematic code:** ``` class Fruit: COLORS = [] def __init__(self, color): self.color = color def pick_colors(cls, *args): """classmethod to pick fruit colors""" cls.COLORS = args pick_colors = classmethod(pick_colors) # [no-classmethod-decorator] ``` **Correct code:** ``` class Fruit: COLORS = [] def __init__(self, color): self.color = color @classmethod def pick_colors(cls, *args): """classmethod to pick fruit colors""" cls.COLORS = args ``` Created by the classes \ checker. ### no-else-break / R1723 **Message emitted:** **Unnecessary "%s" after "break", %s** **Description:** *Used in order to highlight an unnecessary block of code following an if containing a break statement. As such, it will warn when it encounters an else following a chain of ifs, all of them containing a break statement.* **Problematic code:** ``` def next_seven_elements(iterator): for i, item in enumerate(iterator): if i == 7: # [no-else-break] break else: yield item ``` **Correct code:** ``` def next_seven_elements(iterator): for i, item in enumerate(iterator): if i == 7: break yield item ``` Created by the refactoring \ checker. ### no-else-continue / R1724 **Message emitted:** **Unnecessary "%s" after "continue", %s** **Description:** *Used in order to highlight an unnecessary block of code following an if containing a continue statement. As such, it will warn when it encounters an else following a chain of ifs, all of them containing a continue statement.* **Problematic code:** ``` def even_number_under(n: int): for i in range(n): if i % 2 == 1: # [no-else-continue] continue else: yield i ``` **Correct code:** ``` def even_number_under(n: int): for i in range(n): if i % 2 == 1: continue yield i ``` Created by the refactoring \ checker. ### no-else-raise / R1720 **Message emitted:** **Unnecessary "%s" after "raise", %s** **Description:** *Used in order to highlight an unnecessary block of code following an if, or a try/except containing a raise statement. As such, it will warn when it encounters an else following a chain of ifs, all of them containing a raise statement.* **Problematic code:** ``` def integer_sum(a: int, b: int) -> int: if not (isinstance(a, int) and isinstance(b, int)): # [no-else-raise] raise ValueError("Function supports only integer parameters.") else: return a + b ``` **Correct code:** ``` def integer_sum(a: int, b: int) -> int: if not (isinstance(a, int) and isinstance(b, int)): raise ValueError("Function supports only integer parameters.") return a + b ``` Created by the refactoring \ checker. ### no-else-return / R1705 **Message emitted:** **Unnecessary "%s" after "return", %s** **Description:** *Used in order to highlight an unnecessary block of code following an if, or a try/except containing a return statement. As such, it will warn when it encounters an else following a chain of ifs, all of them containing a return statement.* **Problematic code:** ``` def compare_numbers(a: int, b: int) -> int: if a == b: # [no-else-return] return 0 elif a < b: return -1 else: return 1 ``` **Correct code:** ``` def compare_numbers(a: int, b: int) -> int: if a == b: return 0 if a < b: return -1 return 1 ``` Created by the refactoring \ checker. ### no-self-use / R6301 **Message emitted:** **Method could be a function** **Description:** *Used when a method doesn't use its bound instance, and so could be written as a function.* **Problematic code:** ``` class Person: def greeting(self): # [no-self-use] print("Greetings pythonista!") ``` **Correct code:** **function.py**: ``` def greeting(): print("Greetings pythonista!") ``` **staticmethod.py**: ``` class Person: @staticmethod def greeting(): print("Greetings pythonista!") ``` **use\_self.py**: ``` class Person: name: str = "Amelia" def greeting(self): print(f"Greetings {self.name} the pythonista!") ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.no_self_use, ``` **Additional details:** If a function is not using any class attribute it can be a **@staticmethod**, or a function outside the class. **Note:** This message is emitted by the optional 'no\_self\_use' \<#pylint-extensions-no-self-use\> checker, which requires the **pylint.extensions.no\_self\_use** plugin to be loaded. Created by the no\_self\_use \ checker. ### no-staticmethod-decorator / R0203 **Message emitted:** **Consider using a decorator instead of calling staticmethod** **Description:** *Used when a static method is defined without using the decorator syntax.* **Problematic code:** ``` class Worm: def bore(self): pass bore = staticmethod(bore) # [no-staticmethod-decorator] ``` **Correct code:** ``` class Worm: @staticmethod def bore(self): pass ``` Created by the classes \ checker. ### prefer-typing-namedtuple / R6105 **Message emitted:** **Prefer 'typing.NamedTuple' over 'collections.namedtuple'** **Description:** *'typing.NamedTuple' uses the well-known 'class' keyword with type-hints for readability (it's also faster as it avoids an internal exec call).* *Disabled by default!* **Caution:** This message is disabled by default. To enable it, add **prefer-typing-namedtuple** to the **enable** option. **Problematic code:** ``` from collections import namedtuple Philosophy = namedtuple( # [prefer-typing-namedtuple] "Philosophy", ("goodness", "truth", "beauty") ) ``` **Correct code:** ``` from typing import NamedTuple class Philosophy(NamedTuple): goodness: str truth: bool beauty: float ``` **Configuration file:** ``` [MAIN] load-plugins = pylint.extensions.code_style ``` **Related links:** - • typing.NamedTuple \ **Note:** This message is emitted by the optional 'code\_style' \<#pylint-extensions-code-style\> checker, which requires the **pylint.extensions.code\_style** plugin to be loaded. Created by the code\_style \ checker. ### property-with-parameters / R0206 **Message emitted:** **Cannot have defined parameters for properties** **Description:** *Used when we detect that a property also has parameters, which are useless, given that properties cannot be called with additional arguments.* **Problematic code:** ``` class Worm: @property def bore(self, depth): # [property-with-parameters] pass ``` **Correct code:** ``` class Worm: @property def bore(self): """Property accessed with '.bore'.""" pass def bore_with_depth(depth): """Function called with .bore_with_depth(depth).""" pass ``` Created by the classes \ checker. ### redefined-argument-from-local / R1704 **Message emitted:** **Redefining argument with the local name %r** **Description:** *Used when a local name is redefining an argument, which might suggest a potential error. This is taken in account only for a handful of name binding operations, such as for iteration, with statement assignment and exception handler assignment.* **Problematic code:** ``` def show(host_id=10.11): # +1: [redefined-argument-from-local] for host_id, host in [[12.13, "Venus"], [14.15, "Mars"]]: print(host_id, host) ``` **Correct code:** ``` def show(host_id=10.11): for inner_host_id, host in [[12.13, "Venus"], [14.15, "Mars"]]: print(host_id, inner_host_id, host) ``` Created by the refactoring \ checker. ### redefined-variable-type / R0204 **Message emitted:** **Redefinition of %s type from %s to %s** **Description:** *Used when the type of a variable changes inside a method or a function.* **Problematic code:** ``` x = 1 x = "2" # [redefined-variable-type] ``` **Correct code:** ``` x = 1 x = 2 ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.redefined_variable_type, ``` **Note:** This message is emitted by the optional 'multiple\_types' \<#pylint-extensions-redefined-variable-type\> checker, which requires the **pylint.extensions.redefined\_variable\_type** plugin to be loaded. Created by the multiple\_types \ checker. ### redundant-typehint-argument / R6006 **Message emitted:** **Type \`%s\` is used more than once in union type annotation. Remove redundant typehints.** **Description:** *Duplicated type arguments will be skipped by \`mypy\` tool, therefore should be removed to avoid confusion.* **Problematic code:** ``` from typing import Union sweet_count: Union[int, str, int] = 42 # [redundant-typehint-argument] ``` **Correct code:** ``` from typing import Union sweet_count: Union[str, int] = 42 ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.typing ``` **Note:** This message is emitted by the optional 'typing' \<#pylint-extensions-typing\> checker, which requires the **pylint.extensions.typing** plugin to be loaded. Created by the typing \ checker. ### simplifiable-condition / R1726 **Message emitted:** **Boolean condition "%s" may be simplified to "%s"** **Description:** *Emitted when a boolean condition is able to be simplified.* **Problematic code:** ``` def has_apples(apples) -> bool: return bool(apples or False) # [simplifiable-condition] ``` **Correct code:** ``` def has_apples(apples) -> bool: return bool(apples) ``` Created by the refactoring \ checker. ### simplifiable-if-expression / R1719 **Message emitted:** **The if expression can be replaced with %s** **Description:** *Used when an if expression can be replaced with 'bool(test)' or simply 'test' if the boolean cast is implicit.* **Problematic code:** ``` FLYING_THINGS = ["bird", "plane", "superman", "this example"] def is_flying_thing(an_object): return True if an_object in FLYING_THINGS else False # [simplifiable-if-expression] def is_not_flying_thing(an_object): return False if an_object in FLYING_THINGS else True # [simplifiable-if-expression] ``` **Correct code:** ``` FLYING_THINGS = ["bird", "plane", "superman", "this example"] def is_flying_thing(an_object): return an_object in FLYING_THINGS def is_not_flying_thing(an_object): return an_object not in FLYING_THINGS ``` **Related links:** - • Simplifying an 'if' statement with bool() \ Created by the refactoring \ checker. ### simplifiable-if-statement / R1703 **Message emitted:** **The if statement can be replaced with %s** **Description:** *Used when an if statement can be replaced with 'bool(test)'.* **Problematic code:** ``` FLYING_THINGS = ["bird", "plane", "superman", "this example"] def is_flying_animal(an_object): # +1: [simplifiable-if-statement] if isinstance(an_object, Animal) and an_object in FLYING_THINGS: is_flying = True else: is_flying = False return is_flying ``` **Correct code:** ``` FLYING_THINGS = ["bird", "plane", "superman", "this example"] def is_flying_animal(an_object): is_flying = isinstance(an_object, Animal) and an_object.name in FLYING_THINGS return is_flying ``` Created by the refactoring \ checker. ### simplify-boolean-expression / R1709 **Message emitted:** **Boolean expression may be simplified to %s** **Description:** *Emitted when redundant pre-python 2.5 ternary syntax is used.* **Problematic code:** ``` def has_oranges(oranges, apples=None) -> bool: return apples and False or oranges # [simplify-boolean-expression] ``` **Correct code:** ``` def has_oranges(oranges, apples=None) -> bool: return oranges ``` Created by the refactoring \ checker. ### stop-iteration-return / R1708 **Message emitted:** **Do not raise StopIteration in generator, use return statement instead** **Description:** *According to PEP479, the raise of StopIteration to end the loop of a generator may lead to hard to find bugs. This PEP specify that raise StopIteration has to be replaced by a simple return statement* **Problematic code:** **fruit\_generator.py**: ``` def fruit_generator(): for fruit in ["apple", "banana"]: yield fruit raise StopIteration # [stop-iteration-return] ``` **two\_fruit\_generator.py**: ``` def two_fruits_generator(fruits): for fruit in fruits: yield fruit, next(fruits) # [stop-iteration-return] ``` **two\_good\_fruit\_generator.py**: ``` def two_good_fruits_generator(fruits): for fruit in fruits: if not fruit.is_tasty(): continue while True: next_fruit = next(fruits) # [stop-iteration-return] if next_fruit.is_tasty(): yield fruit, next_fruit break ``` **Correct code:** **fruit\_generator.py**: ``` def fruit_generator(): """The example is simple enough you don't need an explicit return.""" for fruit in ["apple", "banana"]: yield fruit ``` **two\_fruit\_generator.py**: ``` def two_fruits_generator(fruits): """Catching the StopIteration.""" for fruit in fruits: try: yield fruit, next(fruits) except StopIteration: print("Sorry there is only one fruit left.") yield fruit, None ``` **two\_good\_fruit\_generator.py**: ``` def two_good_fruits_generator(fruits): """A return can be used to end the iterator early, but not a StopIteration.""" for fruit in fruits: if not fruit.is_tasty(): continue while True: next_fruit = next(fruits, None) if next_fruit is None: print("Sorry there is only one fruit left.") yield fruit, None # We reached the end of the 'fruits' generator but raising a # StopIteration instead of returning would create a RuntimeError return if next_fruit.is_tasty(): yield fruit, next_fruit break ``` **Additional details:** It's possible to give a default value to **next** or catch the **StopIteration**, or return directly. A **StopIteration** cannot be propagated from a generator. **Related links:** - • PEP 479 \ Created by the refactoring \ checker. ### super-with-arguments / R1725 **Message emitted:** **Consider using Python 3 style super() without arguments** **Description:** *Emitted when calling the super() builtin with the current class and instance. On Python 3 these arguments are the default and they can be omitted.* **Problematic code:** ``` class Fruit: pass class Orange(Fruit): def __init__(self): super(Orange, self).__init__() # [super-with-arguments] ``` **Correct code:** ``` class Fruit: pass class Orange(Fruit): def __init__(self): super().__init__() ``` Created by the refactoring \ checker. ### too-complex / R1260 **Message emitted:** **%s is too complex. The McCabe rating is %d** **Description:** *Used when a method or function is too complex based on McCabe Complexity Cyclomatic* **Problematic code:** ``` def fifty_percent_off(whole): return (float(whole)) * 50 / 100 def calculate_sum_and_display_price_of_fruits(*fruits): # [too-complex] # McCabe rating is 13 here (by default 10) shopping_list = [] if "apple" in fruits: v = fifty_percent_off(1.1) shopping_list.append(v) if "pear" in fruits: shopping_list.append(0.8) if "banana" in fruits: shopping_list.append(1.2) if "mango" in fruits: shopping_list.append(3.5) if "peach" in fruits: shopping_list.append(0.5) if "melon" in fruits: shopping_list.append(4.9) if "orange" in fruits: shopping_list.append(2.0) if "strawberry" in fruits: shopping_list.append(2.5) if "mandarin" in fruits: shopping_list.append(2.3) if "plum" in fruits: shopping_list.append(0.5) if "watermelon" in fruits: v = fifty_percent_off(6.4) shopping_list.append(v) combine = zip(fruits, shopping_list) for i in combine: print(f"{i[0]} ${i[1]:.2f}") total = sum(shopping_list) print(f"Total price is ${total:.2f}") fruits_to_buy = ["apple", "orange", "watermelon"] calculate_sum_and_display_price_of_fruits(*fruits_to_buy) ``` **Correct code:** ``` FRUIT_PRICES = { "apple": 1.1, "pear": 0.8, "banana": 1.2, "mango": 3.5, "peach": 0.5, "melon": 4.9, "orange": 2.0, "strawberry": 2.5, "mandarin": 2.3, "plum": 0.5, "watermelon": 6.4, } DISCOUNTED_FRUITS = ["apple", "watermelon"] def fifty_percent_off(whole): return (float(whole)) * 50 / 100 def get_price(fruit): full_price = FRUIT_PRICES.get(fruit) if fruit in DISCOUNTED_FRUITS: return fifty_percent_off(full_price) else: return full_price def display_fruit_and_price(fruits): for fruit in fruits: print(f"{fruit} ${get_price(fruit) :.2f}") def get_total(fruits): return sum(get_price(f) for f in fruits) fruits_to_buy = ["apple", "orange", "watermelon"] display_fruit_and_price(fruits_to_buy) print(f"Total price is ${get_total(fruits_to_buy):.2f}") ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.mccabe ``` **Note:** This message is emitted by the optional 'design' \<#pylint-extensions-mccabe\> checker, which requires the **pylint.extensions.mccabe** plugin to be loaded. Created by the design \ checker. ### too-few-public-methods / R0903 **Message emitted:** **Too few public methods (%s/%s)** **Description:** *Used when class has too few public methods, so be sure it's really worth it.* **Problematic code:** ``` class Worm: # [too-few-public-methods] def __init__(self, name: str, fruit_of_residence: Fruit): self.name = name self.fruit_of_residence = fruit_of_residence def bore(self): print(f"{self.name} is boring into {self.fruit_of_residence}") ``` **Correct code:** **dataclass\_and\_function.py**: ``` import dataclasses @dataclasses.dataclass class Worm: name: str fruit_of_residence: Fruit def bore(worm: Worm): print(f"{worm.name} is boring into {worm.fruit_of_residence}") ``` **function.py**: ``` def bore(fruit: Fruit, worm_name: str): print(f"{worm_name} is boring into {fruit}") ``` **larger\_api.py**: ``` class Worm: def __init__(self, name: str, fruit_of_residence: Fruit): self.name = name self.fruit_of_residence = fruit_of_residence def bore(self): print(f"{self.name} is boring into {self.fruit_of_residence}") def wiggle(self): print(f"{self.name} wiggle around wormily.") ``` Created by the design \ checker. ### too-many-ancestors / R0901 **Message emitted:** **Too many ancestors (%s/%s)** **Description:** *Used when class has too many parent classes, try to reduce this to get a simpler (and so easier to use) class.* **Problematic code:** ``` class Animal: ... class BeakyAnimal(Animal): ... class FurryAnimal(Animal): ... class Swimmer(Animal): ... class EggLayer(Animal): ... class VenomousAnimal(Animal): ... class ProtectedSpecie(Animal): ... class BeaverTailedAnimal(Animal): ... class Vertebrate(Animal): ... # max of 7 by default, can be configured # each edge of a diamond inheritance counts class Playtypus( # [too-many-ancestors] BeakyAnimal, FurryAnimal, Swimmer, EggLayer, VenomousAnimal, ProtectedSpecie, BeaverTailedAnimal, Vertebrate, ): pass ``` **Correct code:** ``` class Animal: beaver_tailed: bool can_swim: bool has_beak: bool has_fur: bool has_vertebrae: bool lays_egg: bool protected_specie: bool venomous: bool class Invertebrate(Animal): has_vertebrae = False class Vertebrate(Animal): has_vertebrae = True class Mammal(Vertebrate): has_beak = False has_fur = True lays_egg = False venomous = False class Playtypus(Mammal): beaver_tailed = True can_swim = True has_beak = True lays_egg = True protected_specie = True venomous = True ``` Created by the design \ checker. ### too-many-arguments / R0913 **Message emitted:** **Too many arguments (%s/%s)** **Description:** *Used when a function or method takes too many arguments.* **Problematic code:** ``` def three_d_chess_move( # [too-many-arguments] x_white, y_white, z_white, piece_white, x_black, y_black, z_black, piece_black, x_blue, y_blue, z_blue, piece_blue, current_player, ): pass ``` **Correct code:** ``` from dataclasses import dataclass @dataclass class ThreeDChessPiece: x: int y: int z: int type: str def three_d_chess_move( white: ThreeDChessPiece, black: ThreeDChessPiece, blue: ThreeDChessPiece, current_player, ): pass ``` Created by the design \ checker. ### too-many-boolean-expressions / R0916 **Message emitted:** **Too many boolean expressions in if statement (%s/%s)** **Description:** *Used when an if statement contains too many boolean expressions.* **Problematic code:** ``` def can_be_divided_by_two_and_are_not_zero(x, y, z): # Maximum number of boolean expressions in an if statement (by default 5) # +1: [too-many-boolean-expressions] if (x and y and z) and (x % 2 == 0 and y % 2 == 0 and z % 2 == 0): pass ``` **Correct code:** ``` def can_be_divided_by_two_and_are_not_zero(x, y, z): if all(i and i % 2 == 0 for i in [x, y, z]): pass ``` Created by the design \ checker. ### too-many-branches / R0912 **Message emitted:** **Too many branches (%s/%s)** **Description:** *Used when a function or method has too many branches, making it hard to follow.* **Problematic code:** ``` def num_to_word(x): # [too-many-branches] if x == 0: return "zero" elif x == 1: return "one" elif x == 2: return "two" elif x == 3: return "three" elif x == 4: return "four" elif x == 5: return "five" elif x == 6: return "six" elif x == 7: return "seven" elif x == 8: return "eight" elif x == 9: return "nine" else: return None ``` **Correct code:** ``` def num_to_word(x): return { 0: "zero", 1: "one", 2: "two", 3: "three", 4: "four", 5: "five", 6: "six", 7: "seven", 8: "eight", 9: "nine", }.get(x) ``` **Configuration file:** ``` [main] max-branches=10 ``` Created by the design \ checker. ### too-many-instance-attributes / R0902 **Message emitted:** **Too many instance attributes (%s/%s)** **Description:** *Used when class has too many instance attributes, try to reduce this to get a simpler (and so easier to use) class.* **Problematic code:** ``` class Fruit: # [too-many-instance-attributes] def __init__(self): # max of 7 attributes by default, can be configured self.worm_name = "Jimmy" self.worm_type = "Codling Moths" self.worm_color = "light brown" self.fruit_name = "Little Apple" self.fruit_color = "Bright red" self.fruit_vitamins = ["A", "B1"] self.fruit_antioxidants = None self.secondary_worm_name = "Kim" self.secondary_worm_type = "Apple maggot" self.secondary_worm_color = "Whitish" ``` **Correct code:** ``` import dataclasses @dataclasses.dataclass class Worm: name: str type: str color: str class Fruit: def __init__(self): self.name = "Little Apple" self.color = "Bright red" self.vitamins = ["A", "B1"] self.antioxidants = None self.worms = [ Worm(name="Jimmy", type="Codling Moths", color="light brown"), Worm(name="Kim", type="Apple maggot", color="Whitish"), ] ``` Created by the design \ checker. ### too-many-locals / R0914 **Message emitted:** **Too many local variables (%s/%s)** **Description:** *Used when a function or method has too many local variables.* **Problematic code:** ``` from childhood import Child, Sweet def handle_sweets(infos): # [too-many-locals] # Create children children = [Child(info) for info in infos] number_of_sweets = 87 sweets = [Sweet() * number_of_sweets] number_of_sweet_per_child = 5 money = 45.0 sweets_given = 0 time_to_eat_sweet = 54 price_of_sweet = 0.42 # distribute sweet for child in children: sweets_given += number_of_sweet_per_child child.give(sweets[number_of_sweet_per_child:]) # calculate prices cost_of_children = sweets_given * price_of_sweet # Calculate remaining money remaining_money = money - cost_of_children # Calculate time it took time_it_took_assuming_parallel_eating = ( time_to_eat_sweet * number_of_sweet_per_child ) print( f"{children} ate {cost_of_children}¤ of sweets in {time_it_took_assuming_parallel_eating}, " f"you still have {remaining_money}" ) ``` **Correct code:** ``` from typing import NamedTuple from childhood import Child, Sweet class SweetDistrubutionCharacteristics(NamedTuple): number_of_sweets: int number_of_sweet_per_child: int number_of_children: int @property def sweets_given(self): return self.number_of_sweet_per_child * self.number_of_children def handle_sweets(infos): children = [Child(info) for info in infos] characteristics = SweetDistrubutionCharacteristics(87, 5, len(children)) _allocate_sweets_to_children(children, characteristics) financial_impact = _assess_financial_impact(characteristics) print(f"{children} ate {financial_impact}") def _allocate_sweets_to_children( children, characteristics: SweetDistrubutionCharacteristics ) -> None: sweets = [Sweet() * characteristics.number_of_sweets] for child in children: child.give(sweets[characteristics.number_of_sweet_per_child :]) def _assess_financial_impact(characteristics: SweetDistrubutionCharacteristics) -> str: time_to_eat_sweet = 54 money = 45.0 price_of_sweet = 0.42 cost_of_children = characteristics.sweets_given * price_of_sweet remaining_money = money - cost_of_children time_it_took_assuming_parallel_eating = ( time_to_eat_sweet * characteristics.number_of_sweet_per_child ) return ( f"{cost_of_children}¤ of sweets in " f"{time_it_took_assuming_parallel_eating}, you still have {remaining_money}" ) ``` **Configuration file:** ``` [design] max-locals = 11 ``` **Additional details:** Having too many locals may indicate that you're doing too much in a function and that classes regrouping some attributes could be created. Maybe operations could be separated in multiple functions. Are all your variables really closely related ? Created by the design \ checker. ### too-many-nested-blocks / R1702 **Message emitted:** **Too many nested blocks (%s/%s)** **Description:** *Used when a function or a method has too many nested blocks. This makes the code less understandable and maintainable.* **Problematic code:** ``` def correct_fruits(fruits): if len(fruits) > 1: # [too-many-nested-blocks] if "apple" in fruits: if "orange" in fruits: count = fruits["orange"] if count % 2: if "kiwi" in fruits: if count == 2: return True return False ``` **Correct code:** ``` def correct_fruits(fruits): if len(fruits) > 1 and "apple" in fruits and "orange" in fruits: count = fruits["orange"] if count % 2 and "kiwi" in fruits and count == 2: return True return False ``` Created by the refactoring \ checker. ### too-many-positional-arguments / R0917 **Message emitted:** **Too many positional arguments (%s/%s)** **Description:** *Used when a function has too many positional arguments.* **Problematic code:** ``` # +1: [too-many-positional-arguments] def calculate_drag_force(velocity, area, density, drag_coefficient): """Each argument is positional-or-keyword unless a `/` or `*` is present.""" return 0.5 * drag_coefficient * density * area * velocity**2 drag_force = calculate_drag_force(30, 2.5, 1.225, 0.47) ``` **Correct code:** ``` def calculate_drag_force(*, velocity, area, density, drag_coefficient): """This function is 'Keyword only' for all args due to the '*'.""" return 0.5 * drag_coefficient * density * area * velocity**2 # This is now impossible to do and will raise a TypeError: # drag_force = calculate_drag_force(30, 2.5, 1.225, 0.47) # ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ # TypeError: calculate_drag_force() takes 0 positional arguments but 4 were given # And this is the only way to call 'calculate_drag_force' drag_force = calculate_drag_force( velocity=30, area=2.5, density=1.225, drag_coefficient=0.47 ) ``` **Configuration file:** ``` [DESIGN] max-positional-arguments=3 ``` **Additional details:** Good function signatures don’t have many positional parameters. For almost all interfaces, comprehensibility suffers beyond a handful of arguments. Positional arguments work well for cases where the use cases are self-evident, such as unittest's **assertEqual(first, second, "assert msg")** or **zip(fruits, vegetables)**. There are a few exceptions where four or more positional parameters make sense, for example **rgba(1.0, 0.5, 0.3, 1.0)**, because it uses a very well-known and well-established convention, and using keywords all the time would be a waste of time. **Related links:** - • Special parameters in python \ Created by the design \ checker. ### too-many-public-methods / R0904 **Message emitted:** **Too many public methods (%s/%s)** **Description:** *Used when class has too many public methods, try to reduce this to get a simpler (and so easier to use) class.* **Problematic code:** ``` class SpaceInvaders: # [too-many-public-methods] def __init__(self): pass def fire_laser_beam(self): pass def deploy_shield(self): pass def launch_missile(self): pass def activate_super_laser(self): pass def summon_mothership(self): pass def destroy_planet(self): pass def teleport(self): pass def invoke_aliens(self): pass def invade_earth(self): pass def takeover_galaxy(self): pass ``` **Correct code:** ``` class LaserBeam: def __init__(self): pass def fire(self): pass def activate_super(self): pass def destroy_planet(self): pass class Shield: def deploy(self): pass class Missile: def launch(self): pass class SpaceInvaders: def __init__(self): self.laser = LaserBeam() self.shield = Shield() self.missile = Missile() def summon_mothership(self): pass def destroy_planet(self): pass def teleport(self): pass def invoke_aliens(self): pass def invade_earth(self): pass def takeover_galaxy(self): pass ``` **Configuration file:** ``` [main] max-public-methods=7 ``` **Additional details:** Having too many public methods is an indication that you might not be respecting the Single-responsibility principle (S of SOLID). The class should have only one reason to change, but in the example the spaceship has at least 4 persons that could ask for change to it (laser manager, shield manager, missile manager, teleportation officer...). **Related links:** - • Single-responsibility principle \ Created by the design \ checker. ### too-many-return-statements / R0911 **Message emitted:** **Too many return statements (%s/%s)** **Description:** *Used when a function or method has too many return statement, making it hard to follow.* **Problematic code:** ``` def to_string(x): # [too-many-return-statements] # max of 6 by default, can be configured if x == 1: return "This is one." if x == 2: return "This is two." if x == 3: return "This is three." if x == 4: return "This is four." if x == 5: return "This is five." if x == 6: return "This is six." if x == 7: return "This is seven." ``` **Correct code:** ``` NUMBERS_TO_STRINGS = { 1: "one", 2: "two", 3: "three", 4: "four", 5: "five", 6: "six", 7: "seven", } def to_string(x): return f"This is {NUMBERS_TO_STRINGS.get(x)}." ``` Created by the design \ checker. ### too-many-statements / R0915 **Message emitted:** **Too many statements (%s/%s)** **Description:** *Used when a function or method has too many statements. You should then split it in smaller functions / methods.* **Problematic code:** ``` import random def distribute_candies( # [too-many-statements] children: list[Child], candies_per_child: int ): # This function is a masterpiece of code that embodies the epitome of efficiency # it's also an essential part of a high-priority project with extremely tight deadlines # and there is absolutely no time to refactor it to make it more concise. # The lead developer on the project, who has decades of experience, # has personally reviewed this implementation and deemed it good enough as it is. # The person writing this code has a demanding job and multiple responsibilities, # and simply does not have the luxury of spending time making this code more readable. total_candies = len(children) * candies_per_child eaten_candies = 0 # Counting candies given to each child for child in children: # If a child eat more than 1 candies they're going to eat all # the candies for sure eaten_for_child = random.choices([0, 1, candies_per_child]) print( f"Child {child} gets {candies_per_child} candies and eat {eaten_for_child}" ) remaining_candies_for_children = child.eat_candies(eaten_for_child) if remaining_candies_for_children == 0: print(f"All the candies have been devoured by {child.name}!") else: print( f"{child.name} still have {remaining_candies_for_children} candies left." ) eaten_candies += eaten_for_child return eaten_candies, total_candies ``` **Correct code:** ``` import random def distribute_candies(children: list[Child], candies_per_child: int): total_candies = len(children) * candies_per_child eaten_candies = 0 for child in children: eaten_candies += _distribute_candies_to_child(candies_per_child, child) return eaten_candies, total_candies def _distribute_candies_to_child(candies_per_child: int, child: Child): # If a child eat more than 1 candies they're going to eat all # the candies for sure eaten_for_child = random.choices([0, 1, candies_per_child]) print(f"Child {child} gets {candies_per_child} candies and eat {eaten_for_child}") remaining_candies_for_children = child.eat_candies(eaten_for_child) if remaining_candies_for_children == 0: print(f"All the candies have been devoured by {child.name}!") else: print(f"{child.name} still have {remaining_candies_for_children} candies left.") return eaten_for_child ``` **Configuration file:** ``` [DESIGN] max-statements=7 ``` Created by the design \ checker. ### trailing-comma-tuple / R1707 **Message emitted:** **Disallow trailing comma tuple** **Description:** *In Python, a tuple is actually created by the comma symbol, not by the parentheses. Unfortunately, one can actually create a tuple by misplacing a trailing comma, which can lead to potential weird bugs in your code. You should always use parentheses explicitly for creating a tuple.* **Problematic code:** ``` COMPASS = "north", "south", "east", "west", # [trailing-comma-tuple] ``` **Correct code:** ``` COMPASS = ("north", "south", "east", "west") ``` Created by the refactoring \ checker. ### unnecessary-comprehension / R1721 **Message emitted:** **Unnecessary use of a comprehension, use %s instead.** **Description:** *Instead of using an identity comprehension, consider using the list, dict or set constructor. It is faster and simpler.* **Problematic code:** ``` NUMBERS = [1, 1, 2, 2, 3, 3] UNIQUE_NUMBERS = {number for number in NUMBERS} # [unnecessary-comprehension] ``` **Correct code:** ``` NUMBERS = [1, 1, 2, 2, 3, 3] UNIQUE_NUMBERS = set(NUMBERS) ``` Created by the refactoring \ checker. ### unnecessary-default-type-args / R6007 **Message emitted:** **Type \`%s\` has unnecessary default type args. Change it to \`%s\`.** **Description:** *Emitted when types have default type args which can be omitted. Mainly used for \`typing.Generator\` and \`typing.AsyncGenerator\`.* **Problematic code:** ``` from collections.abc import AsyncGenerator, Generator a1: AsyncGenerator[int, None] # [unnecessary-default-type-args] b1: Generator[int, None, None] # [unnecessary-default-type-args] ``` **Correct code:** ``` from collections.abc import AsyncGenerator, Generator a1: AsyncGenerator[int] b1: Generator[int] ``` **Configuration file:** ``` [main] load-plugins=pylint.extensions.typing ``` **Additional details:** At the moment, this check only works for **Generator** and **AsyncGenerator**. Starting with Python 3.13, the **SendType** and **ReturnType** default to **None**. As such it's no longer necessary to specify them. The **collections.abc** variants don't validate the number of type arguments. Therefore the defaults for these can be used in earlier versions as well. **Related links:** - • Python documentation for AsyncGenerator \ - • Python documentation for Generator \ **Note:** This message is emitted by the optional 'typing' \<#pylint-extensions-typing\> checker, which requires the **pylint.extensions.typing** plugin to be loaded. Created by the typing \ checker. ### unnecessary-dict-index-lookup / R1733 **Message emitted:** **Unnecessary dictionary index lookup, use '%s' instead** **Description:** *Emitted when iterating over the dictionary items (key-item pairs) and accessing the value by index lookup. The value can be accessed directly instead.* **Problematic code:** ``` FRUITS = {"apple": 1, "orange": 10, "berry": 22} for fruit_name, fruit_count in FRUITS.items(): print(FRUITS[fruit_name]) # [unnecessary-dict-index-lookup] ``` **Correct code:** ``` FRUITS = {"apple": 1, "orange": 10, "berry": 22} for fruit_name, fruit_count in FRUITS.items(): print(fruit_count) ``` Created by the refactoring \ checker. ### unnecessary-list-index-lookup / R1736 **Message emitted:** **Unnecessary list index lookup, use '%s' instead** **Description:** *Emitted when iterating over an enumeration and accessing the value by index lookup. The value can be accessed directly instead.* **Problematic code:** ``` letters = ["a", "b", "c"] for index, letter in enumerate(letters): print(letters[index]) # [unnecessary-list-index-lookup] ``` **Correct code:** ``` letters = ["a", "b", "c"] for index, letter in enumerate(letters): print(letter) ``` Created by the refactoring \ checker. ### use-a-generator / R1729 **Message emitted:** **Use a generator instead '%s(%s)'** **Description:** *Comprehension inside of 'any', 'all', 'max', 'min' or 'sum' is unnecessary. A generator would be sufficient and faster.* **Problematic code:** ``` from random import randint all([randint(-5, 5) > 0 for _ in range(10)]) # [use-a-generator] any([randint(-5, 5) > 0 for _ in range(10)]) # [use-a-generator] ``` **Correct code:** ``` from random import randint all(randint(-5, 5) > 0 for _ in range(10)) any(randint(-5, 5) > 0 for _ in range(10)) ``` **Additional details:** By using a generator you can cut the execution tree and exit directly at the first element that is **False** for **all** or **True** for **any** instead of calculating all the elements. Except in the worst possible case where you still need to evaluate everything (all values are True for **all** or all values are false for **any**) performance will be better. **Related links:** - • PEP 289 – Generator Expressions \ - • Benchmark and discussion during initial implementation \ Created by the refactoring \ checker. ### use-dict-literal / R1735 **Message emitted:** **Consider using '%s' instead of a call to 'dict'.** **Description:** *Emitted when using dict() to create a dictionary instead of a literal '{ ... }'. The literal is faster as it avoids an additional function call.* **Problematic code:** **empty\_dict.py**: ``` empty_dict = dict() # [use-dict-literal] ``` **init\_dict\_from\_another.py**: ``` original_dict = {"name": "Sunny", "age": 10, "favorite_color": "yellow"} copied_dict = dict(**original_dict) # [use-dict-literal] ``` **init\_with\_keyword.py**: ``` response_dict = dict(answer="No") # [use-dict-literal] ``` **Correct code:** **empty\_dict.py**: ``` empty_dict = {} ``` **init\_dict\_from\_another.py**: ``` original_dict = {"name": "Sunny", "age": 10, "favorite_color": "yellow"} # shallow copy a dict copied_dict = {**original_dict} ``` **init\_with\_literal.py**: ``` response_dict = {"answer": "No"} ``` **Additional details:** \ This example script shows an 18% increase in performance when using a literal over the constructor in python version 3.10.6. **Related links:** - • Performance Analysis of Python’s dict() vs dict literal \ Created by the refactoring \ checker. ### use-list-literal / R1734 **Message emitted:** **Consider using \[\] instead of list()** **Description:** *Emitted when using list() to create an empty list instead of the literal \[\]. The literal is faster as it avoids an additional function call.* **Problematic code:** ``` empty_list = list() # [use-list-literal] ``` **Correct code:** ``` empty_list = [] ``` Created by the refactoring \ checker. ### use-set-for-membership / R6201 **Message emitted:** **Consider using set for membership test** **Description:** *Membership tests are more efficient when performed on a lookup optimized datatype like \`\`sets\`\`.* **Problematic code:** ``` def fruit_is_dangerous_for_cat(fruit: str) -> bool: """This list is only a silly example, don't make decision regarding your cat diet based on it.""" return fruit in ["cherry", "grapes"] # [use-set-for-membership] ``` **Correct code:** ``` def fruit_is_dangerous_for_cat(fruit: str) -> bool: """This list is only a silly example, don't make decision regarding your cat diet based on it.""" return fruit in {"cherry", "grapes"} ``` **Configuration file:** ``` [MAIN] load-plugins=pylint.extensions.set_membership ``` **Note:** This message is emitted by the optional 'set\_membership' \<#pylint-extensions-set-membership\> checker, which requires the **pylint.extensions.set\_membership** plugin to be loaded. Created by the set\_membership \ checker. ### use-yield-from / R1737 **Message emitted:** **Use 'yield from' directly instead of yielding each element one by one** **Description:** *Yielding directly from the iterator is faster and arguably cleaner code than yielding each element one by one in the loop.* **Problematic code:** ``` def bad_yield_from(generator): for item in generator: # [use-yield-from] yield item ``` **Correct code:** ``` def good_yield_from(generator): yield from generator ``` **Additional details:** **yield from** can be thought of as removing the intermediary (your for loop) between the function caller and the requested generator. This enables the caller to directly communicate with the generator (e.g. using **send()**). This communication is not possible when manually yielding each element one by one in a loop. PEP 380 describes the possibility of adding optimizations specific to **yield from**. It looks like they have not been implemented as of the time of writing. Even without said optimizations, the following snippet shows that **yield from** is marginally faster. ``` $ python3 -m timeit "def yield_from(): yield from range(100)" "for _ in yield_from(): pass" 100000 loops, best of 5: 2.44 usec per loop $ python3 -m timeit "def yield_loop():" " for item in range(100): yield item" "for _ in yield_loop(): pass" 100000 loops, best of 5: 2.49 usec per loop ``` **Related links:** - • PEP 380 \ Created by the refactoring \ checker. ### useless-object-inheritance / R0205 **Message emitted:** **Class %r inherits from object, can be safely removed from bases in python3** **Description:** *Used when a class inherit from object, which under python3 is implicit, hence can be safely removed from bases.* **Problematic code:** ``` class Banana(object): # [useless-object-inheritance] ... ``` **Correct code:** ``` class Banana: ... ``` Created by the classes \ checker. ### useless-return / R1711 **Message emitted:** **Useless return at end of function or method** **Description:** *Emitted when a single "return" or "return None" statement is found at the end of function or method definition. This statement can safely be removed because Python will implicitly return None* **Problematic code:** ``` import sys def print_python_version(): # [useless-return] print(sys.version) return None ``` **Correct code:** ``` import sys def print_python_version(): print(sys.version) ``` Created by the refactoring \ checker. All renamed messages in the refactor category: ### old-no-self-use / R0201 'old-no-self-use' has been renamed. The new message can be found at: ### old-simplifiable-if-statement / R0102 'old-simplifiable-if-statement' has been renamed. The new message can be found at: ### old-too-many-nested-blocks / R0101 'old-too-many-nested-blocks' has been renamed. The new message can be found at: ### Information All messages in the information category: ### bad-inline-option / I0010 **Message emitted:** **Unable to consider inline option %r** **Description:** *Used when an inline option is either badly formatted or can't be used inside modules.* **Caution:** This message is disabled by default. To enable it, add **bad-inline-option** to the **enable** option. **Caution:** By default, this message will not fail the execution (pylint will return 0). To make pylint fail for this message use the **--fail-on=I0010** option or **--fail-on=I** to fail on all enabled informational messages. **Problematic code:** ``` # 2:[bad-inline-option] # pylint: disable line-too-long ``` **Correct code:** ``` # pylint: disable=line-too-long ``` Created by the main \ checker. ### c-extension-no-member / I1101 **Message emitted:** **%s %r has no %r member%s, but source is unavailable. Consider adding this module to extension-pkg-allow-list if you want to perform analysis based on run-time introspection of living objects.** **Description:** *Used when a variable is accessed for non-existent member of C extension. Due to unavailability of source static analysis is impossible, but it may be performed by introspecting living objects in run-time.* **Caution:** By default, this message will not fail the execution (pylint will return 0). To make pylint fail for this message use the **--fail-on=I1101** option or **--fail-on=I** to fail on all enabled informational messages. **Additional details:** **c-extension-no-member** is an informational variant of **no-member** to encourage allowing introspection of C extensions as described in the page \ for **no-member**. Created by the typecheck \ checker. ### deprecated-pragma / I0022 **Message emitted:** **Pragma "%s" is deprecated, use "%s" instead** **Description:** *Some inline pylint options have been renamed or reworked, only the most recent form should be used. NOTE:skip-all is only available with pylint \>= 0.26* **Caution:** This message is disabled by default. To enable it, add **deprecated-pragma** to the **enable** option. **Caution:** By default, this message will not fail the execution (pylint will return 0). To make pylint fail for this message use the **--fail-on=I0022** option or **--fail-on=I** to fail on all enabled informational messages. **Problematic code:** ``` # pylint: disable-msg=eval-used # [deprecated-pragma] ``` **Correct code:** ``` # pylint: disable = eval-used ``` Created by the main \ checker. ### file-ignored / I0013 **Message emitted:** **Ignoring entire file** **Description:** *Used to inform that the file will not be checked* **Caution:** This message is disabled by default. To enable it, add **file-ignored** to the **enable** option. **Caution:** By default, this message will not fail the execution (pylint will return 0). To make pylint fail for this message use the **--fail-on=I0013** option or **--fail-on=I** to fail on all enabled informational messages. **Problematic code:** ``` # pylint: skip-file # -1: [file-ignored] ``` **Correct code:** ``` ``` **Additional details:** There's no checks at all for a file if it starts by **# pylint: skip-file**. Created by the main \ checker. ### locally-disabled / I0011 **Message emitted:** **Locally disabling %s (%s)** **Description:** *Used when an inline option disables a message or a messages category.* **Caution:** This message is disabled by default. To enable it, add **locally-disabled** to the **enable** option. **Caution:** By default, this message will not fail the execution (pylint will return 0). To make pylint fail for this message use the **--fail-on=I0011** option or **--fail-on=I** to fail on all enabled informational messages. **Problematic code:** ``` def wizard_spells(spell_book): # pylint: disable=maybe-no-member # [locally-disabled] for spell in spell_book: print(f"Abracadabra! {spell}.") spell_list = ["Levitation", "Invisibility", "Fireball", "Teleportation"] wizard_spells(spell_list) ``` **Correct code:** ``` def wizard_spells(spell_book): for spell in spell_book: print(f"Abracadabra! {spell}.") spell_list = ["Levitation", "Invisibility", "Fireball", "Teleportation"] wizard_spells(spell_list) ``` Created by the main \ checker. ### raw-checker-failed / I0001 **Message emitted:** **Unable to run raw checkers on built-in module %s** **Description:** *Used to inform that a built-in module has not been checked using the raw checkers.* **Caution:** This message is disabled by default. To enable it, add **raw-checker-failed** to the **enable** option. **Caution:** By default, this message will not fail the execution (pylint will return 0). To make pylint fail for this message use the **--fail-on=I0001** option or **--fail-on=I** to fail on all enabled informational messages. **Additional details:** This warns you that a builtin module was impossible to analyse (an ast node is not pure python). There's nothing to change in your code, this is a warning about astroid and pylint's limitations. Created by the main \ checker. ### suppressed-message / I0020 **Message emitted:** **Suppressed %s (from line %d)** **Description:** *A message was triggered on a line, but suppressed explicitly by a disable= comment in the file. This message is not generated for messages that are ignored due to configuration settings.* **Caution:** This message is disabled by default. To enable it, add **suppressed-message** to the **enable** option. **Caution:** By default, this message will not fail the execution (pylint will return 0). To make pylint fail for this message use the **--fail-on=I0020** option or **--fail-on=I** to fail on all enabled informational messages. **Problematic code:** ``` ### This is a contrived example, to show how suppressed-message works. ### First we enable all messages # pylint: enable=all ### Here we disable two messages so we get two warnings # pylint: disable=locally-disabled, useless-suppression # [suppressed-message, suppressed-message] ### Here we disable a message, so we get a warning for suppressed-message again. "A" # pylint: disable=pointless-statement # [suppressed-message, suppressed-message] ``` **Correct code:** ``` """Instead of a single string somewhere in the file, write a module docstring!""" ``` **Additional details:** **suppressed-message** is simply a way to see messages that would be raised without the disable in your codebase. It should not be activated most of the time. See also **useless-suppression** if you want to see the message that are disabled for no reasons. Created by the main \ checker. ### use-symbolic-message-instead / I0023 **Message emitted:** **%s** **Description:** *Used when a message is enabled or disabled by id.* **Caution:** This message is disabled by default. To enable it, add **use-symbolic-message-instead** to the **enable** option. **Caution:** By default, this message will not fail the execution (pylint will return 0). To make pylint fail for this message use the **--fail-on=I0023** option or **--fail-on=I** to fail on all enabled informational messages. **Problematic code:** ``` fruit_name = "plum" # pylint: disable-next=W0621 def eat(fruit_name: str): # [use-symbolic-message-instead] ... ``` **Correct code:** ``` fruit_name = "plum" # pylint: disable-next=redefined-outer-name def eat(fruit_name: str): ... ``` Created by the miscellaneous \ checker. ### useless-suppression / I0021 **Message emitted:** **Useless suppression of %s** **Description:** *Reported when a message is explicitly disabled for a line or a block of code, but never triggered.* **Caution:** This message is disabled by default. To enable it, add **useless-suppression** to the **enable** option. **Caution:** By default, this message will not fail the execution (pylint will return 0). To make pylint fail for this message use the **--fail-on=I0021** option or **--fail-on=I** to fail on all enabled informational messages. **Problematic code:** ``` fruit_counter = 0 # pylint: disable-next=redefined-outer-name def eat(fruit_name: str): # [useless-suppression] ... ``` **Correct code:** ``` fruit_counter = 0 def eat(fruit_name: str): ... ``` Created by the main \ checker. All renamed messages in the information category: ### deprecated-disable-all / I0014 'deprecated-disable-all' has been renamed. The new message can be found at: ### Messages control In order to control messages, **pylint** accepts the following values: - • a symbolic message: **no-member**, **undefined-variable** etc. - • a numerical ID: **E1101**, **E1102** etc. - • The name of the group of checks. You can grab those with **pylint --list-groups**. For example, you can disable / enable all the checks related to type checking, with **typecheck** or all the checks related to variables with **variables** - • Corresponding category of the checks - • **C** convention related checks - • **R** refactoring related checks - • **W** various warnings - • **E** errors, for probable bugs in the code - • **F** fatal, if an error occurred which prevented **pylint** from doing further processing. - • All the checks with **all** ### Block disables This describes how the pragma controls operate at a code level. The pragma controls can disable / enable: - • All the violations on a single line ``` a, b = ... # pylint: disable=unbalanced-tuple-unpacking ``` - • All the violations on the following line ``` # pylint: disable-next=unbalanced-tuple-unpacking a, b = ... ``` - • All the violations in a single scope ``` def test(): # Disable all the no-member violations in this function # pylint: disable=no-member ... ``` - • All the violations in a *block*. For instance, each separate branch of an **if** statement is considered a separate block, as in the following example: ``` def meth5(self): # pylint: disable=no-member # no error print(self.bla) if self.blop: # pylint: enable=no-member # enable all no-members for this block print(self.blip) else: # This is affected by the scope disable print(self.blip) # pylint: enable=no-member print(self.blip) if self.blop: # pylint: disable=no-member # disable all no-members for this block print(self.blip) else: # This emits a violation print(self.blip) ``` - • If the violation occurs on a block starting line, then it applies only to that line ``` if self.blop: # pylint: disable=no-member; applies only to this line # Here we get an error print(self.blip) else: # error print(self.blip) ``` Here's an example with all these rules in a single place: ``` """pylint option block-disable""" __revision__ = None class Foo(object): """block-disable test""" def __init__(self): pass def meth1(self, arg): """this issues a message""" print(self) def meth2(self, arg): """and this one not""" # pylint: disable=unused-argument print(self\ + "foo") def meth3(self): """test one line disabling""" # no error print(self.bla) # pylint: disable=no-member # error print(self.blop) def meth4(self): """test re-enabling""" # pylint: disable=no-member # no error print(self.bla) print(self.blop) # pylint: enable=no-member # error print(self.blip) def meth5(self): """test IF sub-block re-enabling""" # pylint: disable=no-member # no error print(self.bla) if self.blop: # pylint: enable=no-member # error print(self.blip) else: # no error print(self.blip) # no error print(self.blip) def meth6(self): """test TRY/EXCEPT sub-block re-enabling""" # pylint: disable=no-member # no error print(self.bla) try: # pylint: enable=no-member # error print(self.blip) except UndefinedName: # pylint: disable=undefined-variable # no error print(self.blip) # no error print(self.blip) def meth7(self): """test one line block opening disabling""" if self.blop: # pylint: disable=no-member # error print(self.blip) else: # error print(self.blip) # error print(self.blip) def meth8(self): """test late disabling""" # error print(self.blip) # pylint: disable=no-member # no error print(self.bla) print(self.blop) def meth9(self): """test next line disabling""" # no error # pylint: disable-next=no-member print(self.bla) # error print(self.blop) ``` ### Detecting useless disables As pylint gets better and false positives are removed, disables that became useless can accumulate and clutter the code. In order to clean them you can enable the **useless-suppression** warning. ### Messages categories Pylint can emit various messages. These are categorized according to categories corresponding to bit-encoded exit codes: - • Fatal \<#fatal-category\> (1) - • Error \<#error-category\> (2) - • Warning \<#warning-category\> (4) - • Convention \<#convention-category\> (8) - • Refactor \<#refactor-category\> (16) - • Information \<#information-category\> (NA) An overview of these messages can be found in Messages overview \<#messages-overview\> ### Disabling messages **pylint** has an advanced message control for its checks, offering the ability to enable / disable a message either from the command line or from the configuration file, as well as from the code itself. For more detail see Messages control \<#message-control\> ### Configuration Pylint is highly configurable. There are a lot of options to follow the needs of various projects and a lot of checks to activate if they suit your style. You can generate a sample configuration file with **--generate-toml-config** or **--generate-rcfile**. Every option present on the command line before this will be included in the file. For example: ``` pylint --disable=bare-except,invalid-name --class-rgx='[A-Z][a-z]+' --generate-toml-config ``` In practice, it is often better to create a minimal configuration file which only contains configuration overrides. For all other options, Pylint will use its default values. **Note:** The internals that create the configuration files fall back to the default values if no other value was given. This means that some values depend on the interpreter that was used to generate the file. Most notably **py-version** which defaults to the current interpreter. ### Standard Checkers ### Main Checker ### --analyse-fallback-blocks *Analyse import fallback blocks. This can be used to support both Python 2 and 3 compatible code, which means that the block might have code that exists only in one or another interpreter, leading to false positives when analysed.* **Default:** **False** ### --clear-cache-post-run *Clear in-memory caches upon conclusion of linting. Useful if running pylint in a server-like mode.* **Default:** **False** ### --confidence *Only show warnings with the listed confidence levels. Leave empty to show all. Valid levels: HIGH, CONTROL\_FLOW, INFERENCE, INFERENCE\_FAILURE, UNDEFINED.* **Default:** **\['HIGH', 'CONTROL\_FLOW', 'INFERENCE', 'INFERENCE\_FAILURE', 'UNDEFINED'\]** ### --disable *Disable the message, report, category or checker with the given id(s). You can either give multiple identifiers separated by comma (,) or put this option multiple times (only on the command line, not in the configuration file where it should appear only once). You can also use "--disable=all" to disable everything first and then re-enable specific checks. For example, if you want to run only the similarities checker, you can use "--disable=all --enable=similarities". If you want to run only the classes checker, but have no Warning level messages displayed, use "--disable=all --enable=classes --disable=W".* **Default:** **()** ### --enable *Enable the message, report, category or checker with the given id(s). You can either give multiple identifier separated by comma (,) or put this option multiple time (only on the command line, not in the configuration file where it should appear only once). See also the "--disable" option for examples.* **Default:** **()** ### --evaluation *Python expression which should return a score less than or equal to 10. You have access to the variables 'fatal', 'error', 'warning', 'refactor', 'convention', and 'info' which contain the number of messages in each category, as well as 'statement' which is the total number of statements analyzed. This score is used by the global evaluation report (RP0004).* **Default:** **max(0, 0 if fatal else 10.0 - ((float(5 \* error + warning + refactor + convention) / statement) \* 10))** ### --exit-zero *Always return a 0 (non-error) status code, even if lint errors are found. This is primarily useful in continuous integration scripts.* **Default:** **False** ### --extension-pkg-allow-list *A comma-separated list of package or module names from where C extensions may be loaded. Extensions are loading into the active Python interpreter and may run arbitrary code.* **Default:** **\[\]** ### --extension-pkg-whitelist *A comma-separated list of package or module names from where C extensions may be loaded. Extensions are loading into the active Python interpreter and may run arbitrary code. (This is an alternative name to extension-pkg-allow-list for backward compatibility.)* **Default:** **\[\]** ### --fail-on *Return non-zero exit code if any of these messages/categories are detected, even if score is above --fail-under value. Syntax same as enable. Messages specified are enabled, while categories only check already-enabled messages.* **Default:** **""** ### --fail-under *Specify a score threshold under which the program will exit with error.* **Default:** **10** ### --from-stdin *Interpret the stdin as a python script, whose filename needs to be passed as the module\_or\_package argument.* **Default:** **False** ### --ignore *Files or directories to be skipped. They should be base names, not paths.* **Default:** **('CVS',)** ### --ignore-paths *Add files or directories matching the regular expressions patterns to the ignore-list. The regex matches against paths and can be in Posix or Windows format. Because '\\' represents the directory delimiter on Windows systems, it can't be used as an escape character.* **Default:** **\[\]** ### --ignore-patterns *Files or directories matching the regular expression patterns are skipped. The regex matches against base names, not paths. The default value ignores Emacs file locks* **Default:** **(re.compile('^\\\\.#'),)** ### --ignored-modules *List of module names for which member attributes should not be checked and will not be imported (useful for modules/projects where namespaces are manipulated during runtime and thus existing member attributes cannot be deduced by static analysis). It supports qualified module names, as well as Unix pattern matching.* **Default:** **()** ### --jobs *Use multiple processes to speed up Pylint. Specifying 0 will auto-detect the number of processors available to use, and will cap the count on Windows to avoid hangs.* **Default:** **1** ### --limit-inference-results *Control the amount of potential inferred values when inferring a single object. This can help the performance when dealing with large functions or complex, nested conditions.* **Default:** **100** ### --load-plugins *List of plugins (as comma separated values of python module names) to load, usually to register additional checkers.* **Default:** **()** ### --msg-template *Template used to display messages. This is a python new-style format string used to format the message information. See doc for all details.* **Default:** **""** ### --output-format *Set the output format. Available formats are: 'text', 'parseable', 'colorized', 'json2' (improved json format), 'json' (old json format), msvs (visual studio) and 'github' (GitHub actions). You can also give a reporter class, e.g. mypackage.mymodule.MyReporterClass.* **Default:** **text** ### --persistent *Pickle collected data for later comparisons.* **Default:** **True** ### --prefer-stubs *Resolve imports to .pyi stubs if available. May reduce no-member messages and increase not-an-iterable messages.* **Default:** **False** ### --py-version *Minimum Python version to use for version dependent checks. Will default to the version used to run pylint.* **Default:** **sys.version\_info\[:2\]** ### --recursive *Discover python modules and packages in the file system subtree.* **Default:** **False** ### --reports *Tells whether to display a full report or only the messages.* **Default:** **False** ### --score *Activate the evaluation score.* **Default:** **True** ### --source-roots *Add paths to the list of the source roots. Supports globbing patterns. The source root is an absolute path or a path relative to the current working directory used to determine a package namespace for modules located under the source root.* **Default:** **()** ### --unsafe-load-any-extension *Allow loading of arbitrary C extensions. Extensions are imported into the active Python interpreter and may run arbitrary code.* **Default:** **False** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.main] analyse-fallback-blocks = false clear-cache-post-run = false confidence = ["HIGH", "CONTROL_FLOW", "INFERENCE", "INFERENCE_FAILURE", "UNDEFINED"] disable = ["bad-inline-option", "consider-using-augmented-assign", "deprecated-pragma", "file-ignored", "locally-disabled", "prefer-typing-namedtuple", "raw-checker-failed", "suppressed-message", "use-implicit-booleaness-not-comparison-to-string", "use-implicit-booleaness-not-comparison-to-zero", "use-symbolic-message-instead", "useless-suppression"] enable = [] evaluation = "max(0, 0 if fatal else 10.0 - ((float(5 * error + warning + refactor + convention) / statement) * 10))" exit-zero = false extension-pkg-allow-list = [] extension-pkg-whitelist = [] fail-on = [] fail-under = 10 from-stdin = false ignore = ["CVS"] ignore-paths = [] ignore-patterns = ["^\\.#"] ignored-modules = [] jobs = 1 limit-inference-results = 100 load-plugins = [] msg-template = "" # output-format = persistent = true prefer-stubs = false py-version = "sys.version_info[:2]" recursive = false reports = false score = true source-roots = [] unsafe-load-any-extension = false ``` ### Basic Checker ### --argument-naming-style *Naming style matching correct argument names.* **Default:** **snake\_case** ### --argument-rgx *Regular expression matching correct argument names. Overrides argument-naming-style. If left empty, argument names will be checked with the set naming style.* **Default:** **None** ### --attr-naming-style *Naming style matching correct attribute names.* **Default:** **snake\_case** ### --attr-rgx *Regular expression matching correct attribute names. Overrides attr-naming-style. If left empty, attribute names will be checked with the set naming style.* **Default:** **None** ### --bad-names *Bad variable names which should always be refused, separated by a comma.* **Default:** **('foo', 'bar', 'baz', 'toto', 'tutu', 'tata')** ### --bad-names-rgxs *Bad variable names regexes, separated by a comma. If names match any regex, they will always be refused* **Default:** **""** ### --class-attribute-naming-style *Naming style matching correct class attribute names.* **Default:** **any** ### --class-attribute-rgx *Regular expression matching correct class attribute names. Overrides class-attribute-naming-style. If left empty, class attribute names will be checked with the set naming style.* **Default:** **None** ### --class-const-naming-style *Naming style matching correct class constant names.* **Default:** **UPPER\_CASE** ### --class-const-rgx *Regular expression matching correct class constant names. Overrides class-const-naming-style. If left empty, class constant names will be checked with the set naming style.* **Default:** **None** ### --class-naming-style *Naming style matching correct class names.* **Default:** **PascalCase** ### --class-rgx *Regular expression matching correct class names. Overrides class-naming-style. If left empty, class names will be checked with the set naming style.* **Default:** **None** ### --const-naming-style *Naming style matching correct constant names.* **Default:** **UPPER\_CASE** ### --const-rgx *Regular expression matching correct constant names. Overrides const-naming-style. If left empty, constant names will be checked with the set naming style.* **Default:** **None** ### --docstring-min-length *Minimum line length for functions/classes that require docstrings, shorter ones are exempt.* **Default:** **-1** ### --function-naming-style *Naming style matching correct function names.* **Default:** **snake\_case** ### --function-rgx *Regular expression matching correct function names. Overrides function-naming-style. If left empty, function names will be checked with the set naming style.* **Default:** **None** ### --good-names *Good variable names which should always be accepted, separated by a comma.* **Default:** **('i', 'j', 'k', 'ex', 'Run', '\_')** ### --good-names-rgxs *Good variable names regexes, separated by a comma. If names match any regex, they will always be accepted* **Default:** **""** ### --include-naming-hint *Include a hint for the correct naming format with invalid-name.* **Default:** **False** ### --inlinevar-naming-style *Naming style matching correct inline iteration names.* **Default:** **any** ### --inlinevar-rgx *Regular expression matching correct inline iteration names. Overrides inlinevar-naming-style. If left empty, inline iteration names will be checked with the set naming style.* **Default:** **None** ### --method-naming-style *Naming style matching correct method names.* **Default:** **snake\_case** ### --method-rgx *Regular expression matching correct method names. Overrides method-naming-style. If left empty, method names will be checked with the set naming style.* **Default:** **None** ### --module-naming-style *Naming style matching correct module names.* **Default:** **snake\_case** ### --module-rgx *Regular expression matching correct module names. Overrides module-naming-style. If left empty, module names will be checked with the set naming style.* **Default:** **None** ### --name-group *Colon-delimited sets of names that determine each other's naming style when the name regexes allow several styles.* **Default:** **()** ### --no-docstring-rgx *Regular expression which should only match function or class names that do not require a docstring.* **Default:** **re.compile('^\_')** ### --paramspec-rgx *Regular expression matching correct parameter specification variable names. If left empty, parameter specification variable names will be checked with the set naming style.* **Default:** **None** ### --property-classes *List of decorators that produce properties, such as abc.abstractproperty. Add to this list to register other decorators that produce valid properties. These decorators are taken in consideration only for invalid-name.* **Default:** **('abc.abstractproperty',)** ### --typealias-rgx *Regular expression matching correct type alias names. If left empty, type alias names will be checked with the set naming style.* **Default:** **None** ### --typevar-rgx *Regular expression matching correct type variable names. If left empty, type variable names will be checked with the set naming style.* **Default:** **None** ### --typevartuple-rgx *Regular expression matching correct type variable tuple names. If left empty, type variable tuple names will be checked with the set naming style.* **Default:** **None** ### --variable-naming-style *Naming style matching correct variable names.* **Default:** **snake\_case** ### --variable-rgx *Regular expression matching correct variable names. Overrides variable-naming-style. If left empty, variable names will be checked with the set naming style.* **Default:** **None** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.basic] # Possible choices: ['snake_case', 'camelCase', 'PascalCase', 'UPPER_CASE', 'any'] argument-naming-style = "snake_case" # argument-rgx = # Possible choices: ['snake_case', 'camelCase', 'PascalCase', 'UPPER_CASE', 'any'] attr-naming-style = "snake_case" # attr-rgx = bad-names = ["foo", "bar", "baz", "toto", "tutu", "tata"] bad-names-rgxs = [] # Possible choices: ['snake_case', 'camelCase', 'PascalCase', 'UPPER_CASE', 'any'] class-attribute-naming-style = "any" # class-attribute-rgx = # Possible choices: ['snake_case', 'camelCase', 'PascalCase', 'UPPER_CASE', 'any'] class-const-naming-style = "UPPER_CASE" # class-const-rgx = # Possible choices: ['snake_case', 'camelCase', 'PascalCase', 'UPPER_CASE', 'any'] class-naming-style = "PascalCase" # class-rgx = # Possible choices: ['snake_case', 'camelCase', 'PascalCase', 'UPPER_CASE', 'any'] const-naming-style = "UPPER_CASE" # const-rgx = docstring-min-length = -1 # Possible choices: ['snake_case', 'camelCase', 'PascalCase', 'UPPER_CASE', 'any'] function-naming-style = "snake_case" # function-rgx = good-names = ["i", "j", "k", "ex", "Run", "_"] good-names-rgxs = [] include-naming-hint = false # Possible choices: ['snake_case', 'camelCase', 'PascalCase', 'UPPER_CASE', 'any'] inlinevar-naming-style = "any" # inlinevar-rgx = # Possible choices: ['snake_case', 'camelCase', 'PascalCase', 'UPPER_CASE', 'any'] method-naming-style = "snake_case" # method-rgx = # Possible choices: ['snake_case', 'camelCase', 'PascalCase', 'UPPER_CASE', 'any'] module-naming-style = "snake_case" # module-rgx = name-group = [] no-docstring-rgx = "^_" # paramspec-rgx = property-classes = ["abc.abstractproperty"] # typealias-rgx = # typevar-rgx = # typevartuple-rgx = # Possible choices: ['snake_case', 'camelCase', 'PascalCase', 'UPPER_CASE', 'any'] variable-naming-style = "snake_case" # variable-rgx = ``` ### Classes Checker ### --check-protected-access-in-special-methods *Warn about protected attribute access inside special methods* **Default:** **False** ### --defining-attr-methods *List of method names used to declare (i.e. assign) instance attributes.* **Default:** **('\_\_init\_\_', '\_\_new\_\_', 'setUp', 'asyncSetUp', '\_\_post\_init\_\_')** ### --exclude-protected *List of member names, which should be excluded from the protected access warning.* **Default:** **('\_asdict', '\_fields', '\_replace', '\_source', '\_make', 'os.\_exit')** ### --valid-classmethod-first-arg *List of valid names for the first argument in a class method.* **Default:** **('cls',)** ### --valid-metaclass-classmethod-first-arg *List of valid names for the first argument in a metaclass class method.* **Default:** **('mcs',)** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.classes] check-protected-access-in-special-methods = false defining-attr-methods = ["__init__", "__new__", "setUp", "asyncSetUp", "__post_init__"] exclude-protected = ["_asdict", "_fields", "_replace", "_source", "_make", "os._exit"] valid-classmethod-first-arg = ["cls"] valid-metaclass-classmethod-first-arg = ["mcs"] ``` ### Design Checker ### --exclude-too-few-public-methods *List of regular expressions of class ancestor names to ignore when counting public methods (see R0903)* **Default:** **\[\]** ### --ignored-parents *List of qualified class names to ignore when counting class parents (see R0901)* **Default:** **()** ### --max-args *Maximum number of arguments for function / method.* **Default:** **5** ### --max-attributes *Maximum number of attributes for a class (see R0902).* **Default:** **7** ### --max-bool-expr *Maximum number of boolean expressions in an if statement (see R0916).* **Default:** **5** ### --max-branches *Maximum number of branch for function / method body.* **Default:** **12** ### --max-complexity *McCabe complexity cyclomatic threshold* **Default:** **10** ### --max-locals *Maximum number of locals for function / method body.* **Default:** **15** ### --max-parents *Maximum number of parents for a class (see R0901).* **Default:** **7** ### --max-positional-arguments *Maximum number of positional arguments for function / method.* **Default:** **5** ### --max-public-methods *Maximum number of public methods for a class (see R0904).* **Default:** **20** ### --max-returns *Maximum number of return / yield for function / method body.* **Default:** **6** ### --max-statements *Maximum number of statements in function / method body.* **Default:** **50** ### --min-public-methods *Minimum number of public methods for a class (see R0903).* **Default:** **2** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.design] exclude-too-few-public-methods = [] ignored-parents = [] max-args = 5 max-attributes = 7 max-bool-expr = 5 max-branches = 12 max-complexity = 10 max-locals = 15 max-parents = 7 max-positional-arguments = 5 max-public-methods = 20 max-returns = 6 max-statements = 50 min-public-methods = 2 ``` ### Exceptions Checker ### --overgeneral-exceptions *Exceptions that will emit a warning when caught.* **Default:** **('builtins.BaseException', 'builtins.Exception')** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.exceptions] overgeneral-exceptions = ["builtins.BaseException", "builtins.Exception"] ``` ### Format Checker ### --expected-line-ending-format *Expected format of line ending, e.g. empty (any line ending), LF or CRLF.* **Default:** **""** ### --ignore-long-lines *Regexp for a line that is allowed to be longer than the limit.* **Default:** **^\\s\*(# )?\?$** ### --indent-after-paren *Number of spaces of indent required inside a hanging or continued line.* **Default:** **4** ### --indent-string *String used as indentation unit. This is usually " " (4 spaces) or "t" (1 tab).* **Default:** \`\` \`\` ### --max-line-length *Maximum number of characters on a single line. Pylint's default of 100 is based on PEP 8's guidance that teams may choose line lengths up to 99 characters.* **Default:** **100** ### --max-module-lines *Maximum number of lines in a module.* **Default:** **1000** ### --single-line-class-stmt *Allow the body of a class to be on the same line as the declaration if body contains single statement.* **Default:** **False** ### --single-line-if-stmt *Allow the body of an if to be on the same line as the test if there is no else.* **Default:** **False** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.format] # Possible choices: ['', 'LF', 'CRLF'] expected-line-ending-format = "" ignore-long-lines = "^\\s*(# )??$" indent-after-paren = 4 indent-string = " " max-line-length = 100 max-module-lines = 1000 single-line-class-stmt = false single-line-if-stmt = false ``` ### Imports Checker ### --allow-any-import-level *List of modules that can be imported at any level, not just the top level one.* **Default:** **()** ### --allow-reexport-from-package *Allow explicit reexports by alias from a package \_\_init\_\_.* **Default:** **False** ### --allow-wildcard-with-all *Allow wildcard imports from modules that define \_\_all\_\_.* **Default:** **False** ### --deprecated-modules *Deprecated modules which should not be used, separated by a comma.* **Default:** **()** ### --ext-import-graph *Output a graph (.gv or any supported image format) of external dependencies to the given file (report RP0402 must not be disabled).* **Default:** **""** ### --import-graph *Output a graph (.gv or any supported image format) of all (i.e. internal and external) dependencies to the given file (report RP0402 must not be disabled).* **Default:** **""** ### --int-import-graph *Output a graph (.gv or any supported image format) of internal dependencies to the given file (report RP0402 must not be disabled).* **Default:** **""** ### --known-standard-library *Force import order to recognize a module as part of the standard compatibility libraries.* **Default:** **()** ### --known-third-party *Force import order to recognize a module as part of a third party library.* **Default:** **('enchant',)** ### --preferred-modules *Couples of modules and preferred modules, separated by a comma.* **Default:** **()** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.imports] allow-any-import-level = [] allow-reexport-from-package = false allow-wildcard-with-all = false deprecated-modules = [] ext-import-graph = "" import-graph = "" int-import-graph = "" known-standard-library = [] known-third-party = ["enchant"] preferred-modules = [] ``` ### Logging Checker ### --logging-format-style *The type of string formatting that logging methods do. \`old\` means using % formatting, \`new\` is for \`{}\` formatting.* **Default:** **old** ### --logging-modules *Logging modules to check that the string format arguments are in logging function parameter format.* **Default:** **('logging',)** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.logging] # Possible choices: ['old', 'new'] logging-format-style = "old" logging-modules = ["logging"] ``` ### Method\_args Checker ### --timeout-methods *List of qualified names (i.e., library.method) which require a timeout parameter e.g. 'requests.api.get,requests.api.post'* **Default:** **('requests.api.delete', 'requests.api.get', 'requests.api.head', 'requests.api.options', 'requests.api.patch', 'requests.api.post', 'requests.api.put', 'requests.api.request')** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.method_args] timeout-methods = ["requests.api.delete", "requests.api.get", "requests.api.head", "requests.api.options", "requests.api.patch", "requests.api.post", "requests.api.put", "requests.api.request"] ``` ### Miscellaneous Checker ### --check-fixme-in-docstring *Whether or not to search for fixme's in docstrings.* **Default:** **False** ### --notes *List of note tags to take in consideration, separated by a comma.* **Default:** **('FIXME', 'XXX', 'TODO')** ### --notes-rgx *Regular expression of note tags to take in consideration.* **Default:** **""** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.miscellaneous] check-fixme-in-docstring = false notes = ["FIXME", "XXX", "TODO"] notes-rgx = "" ``` ### Refactoring Checker ### --max-nested-blocks *Maximum number of nested blocks for function / method body* **Default:** **5** ### --never-returning-functions *Complete name of functions that never returns. When checking for inconsistent-return-statements if a never returning function is called then it will be considered as an explicit return statement and no message will be printed.* **Default:** **('sys.exit', 'argparse.parse\_error')** ### --suggest-join-with-non-empty-separator *Let 'consider-using-join' be raised when the separator to join on would be non-empty (resulting in expected fixes of the type: \`\`"- " + "* *- ".join(items)\`\`)* **Default:** **True** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.refactoring] max-nested-blocks = 5 never-returning-functions = ["sys.exit", "argparse.parse_error"] suggest-join-with-non-empty-separator = true ``` ### Similarities Checker ### --ignore-comments *Comments are removed from the similarity computation* **Default:** **True** ### --ignore-docstrings *Docstrings are removed from the similarity computation* **Default:** **True** ### --ignore-imports *Imports are removed from the similarity computation* **Default:** **True** ### --ignore-signatures *Signatures are removed from the similarity computation* **Default:** **True** ### --min-similarity-lines *Minimum lines number of a similarity.* **Default:** **4** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.similarities] ignore-comments = true ignore-docstrings = true ignore-imports = true ignore-signatures = true min-similarity-lines = 4 ``` ### Spelling Checker ### --max-spelling-suggestions *Limits count of emitted suggestions for spelling mistakes.* **Default:** **4** ### --spelling-dict *Spelling dictionary name. Available dictionaries depends on your local enchant installation* **Default:** **""** ### --spelling-ignore-comment-directives *List of comma separated words that should be considered directives if they appear at the beginning of a comment and should not be checked.* **Default:** **fmt: on,fmt: off,noqa:,noqa,nosec,isort:skip,mypy:** ### --spelling-ignore-words *List of comma separated words that should not be checked.* **Default:** **""** ### --spelling-private-dict-file *A path to a file that contains the private dictionary; one word per line.* **Default:** **""** ### --spelling-store-unknown-words *Tells whether to store unknown words to the private dictionary (see the --spelling-private-dict-file option) instead of raising a message.* **Default:** **n** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.spelling] max-spelling-suggestions = 4 # Possible choices: Values from 'enchant.Broker().list_dicts()' depending on your local enchant installation spelling-dict = "" spelling-ignore-comment-directives = "fmt: on,fmt: off,noqa:,noqa,nosec,isort:skip,mypy:" spelling-ignore-words = "" spelling-private-dict-file = "" spelling-store-unknown-words = false ``` ### String Checker ### --check-quote-consistency *This flag controls whether inconsistent-quotes generates a warning when the character used as a quote delimiter is used inconsistently within a module.* **Default:** **False** ### --check-str-concat-over-line-jumps *This flag controls whether the implicit-str-concat should generate a warning on implicit string concatenation in sequences defined over several lines.* **Default:** **False** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.string] check-quote-consistency = false check-str-concat-over-line-jumps = false ``` ### Typecheck Checker ### --contextmanager-decorators *List of decorators that produce context managers, such as contextlib.contextmanager. Add to this list to register other decorators that produce valid context managers.* **Default:** **\['contextlib.contextmanager'\]** ### --generated-members *List of members which are set dynamically and missed by pylint inference system, and so shouldn't trigger E1101 when accessed. Python regular expressions are accepted.* **Default:** **()** ### --ignore-mixin-members *Tells whether missing members accessed in mixin class should be ignored. A class is considered mixin if its name matches the mixin-class-rgx option.* **Default:** **True** ### --ignore-none *Tells whether to warn about missing members when the owner of the attribute is inferred to be None.* **Default:** **True** ### --ignore-on-opaque-inference *This flag controls whether pylint should warn about no-member and similar checks whenever an opaque object is returned when inferring. The inference can return multiple potential results while evaluating a Python object, but some branches might not be evaluated, which results in partial inference. In that case, it might be useful to still emit no-member and other checks for the rest of the inferred objects.* **Default:** **True** ### --ignored-checks-for-mixins *List of symbolic message names to ignore for Mixin members.* **Default:** **\['no-member', 'not-async-context-manager', 'not-context-manager', 'attribute-defined-outside-init'\]** ### --ignored-classes *List of class names for which member attributes should not be checked (useful for classes with dynamically set attributes). This supports the use of qualified names.* **Default:** **('optparse.Values', 'thread.\_local', '\_thread.\_local', 'argparse.Namespace')** ### --missing-member-hint *Show a hint with possible names when a member name was not found. The aspect of finding the hint is based on edit distance.* **Default:** **True** ### --missing-member-hint-distance *The maximum edit distance a name should have in order to be considered a similar match for a missing member name.* **Default:** **1** ### --missing-member-max-choices *The total number of similar names that should be taken in consideration when showing a hint for a missing member.* **Default:** **1** ### --mixin-class-rgx *Regex pattern to define which classes are considered mixins.* **Default:** **.\*\[Mm\]ixin** ### --signature-mutators *List of decorators that change the signature of a decorated function.* **Default:** **\[\]** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.typecheck] contextmanager-decorators = ["contextlib.contextmanager"] generated-members = [] ignore-mixin-members = true ignore-none = true ignore-on-opaque-inference = true ignored-checks-for-mixins = ["no-member", "not-async-context-manager", "not-context-manager", "attribute-defined-outside-init"] ignored-classes = ["optparse.Values", "thread._local", "_thread._local", "argparse.Namespace"] missing-member-hint = true missing-member-hint-distance = 1 missing-member-max-choices = 1 mixin-class-rgx = ".*[Mm]ixin" signature-mutators = [] ``` ### Variables Checker ### --additional-builtins *List of additional names supposed to be defined in builtins. Remember that you should avoid defining new builtins when possible.* **Default:** **()** ### --allow-global-unused-variables *Tells whether unused global variables should be treated as a violation.* **Default:** **True** ### --allowed-redefined-builtins *List of names allowed to shadow builtins* **Default:** **()** ### --callbacks *List of strings which can identify a callback function by name. A callback name must start or end with one of those strings.* **Default:** **('cb\_', '\_cb')** ### --dummy-variables-rgx *A regular expression matching the name of dummy variables (i.e. expected to not be used).* **Default:** **\_+$\|(\_\[a-zA-Z0-9\_\]\*\[a-zA-Z0-9\]+?$)\|dummy\|^ignored\_\|^unused\_** ### --ignored-argument-names *Argument names that match this expression will be ignored.* **Default:** **re.compile('\_.\*\|^ignored\_\|^unused\_')** ### --init-import *Tells whether we should check for unused import in \_\_init\_\_ files.* **Default:** **False** ### --redefining-builtins-modules *List of qualified module names which can have objects that can redefine builtins.* **Default:** **('six.moves', 'past.builtins', 'future.builtins', 'builtins', 'io')** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.variables] additional-builtins = [] allow-global-unused-variables = true allowed-redefined-builtins = [] callbacks = ["cb_", "_cb"] dummy-variables-rgx = "_+$|(_[a-zA-Z0-9_]*[a-zA-Z0-9]+?$)|dummy|^ignored_|^unused_" ignored-argument-names = "_.*|^ignored_|^unused_" init-import = false redefining-builtins-modules = ["six.moves", "past.builtins", "future.builtins", "builtins", "io"] ``` ### Extensions ### Broad\_try\_clause Checker ### --max-try-statements *Maximum number of statements allowed in a try clause* **Default:** **1** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.broad_try_clause] max-try-statements = 1 ``` ### Code\_style Checker ### --max-line-length-suggestions *Max line length for which to sill emit suggestions. Used to prevent optional suggestions which would get split by a code formatter (e.g., black). Will default to the setting for \`\`max-line-length\`\`.* **Default:** **0** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.code_style] max-line-length-suggestions = 0 ``` ### Deprecated\_builtins Checker ### --bad-functions *List of builtins function names that should not be used, separated by a comma* **Default:** **\['map', 'filter'\]** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.deprecated_builtins] bad-functions = ["map", "filter"] ``` ### Dunder Checker ### --good-dunder-names *Good dunder names which should always be accepted.* **Default:** **\[\]** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.dunder] good-dunder-names = [] ``` ### Magic-value Checker ### --valid-magic-values *List of valid magic values that \`magic-value-compare\` will not detect. Supports integers, floats, negative numbers, for empty string enter \`\`''\`\`, for backslash values just use one backslash e.g n.* **Default:** **(0, -1, 1, '', '\_\_main\_\_')** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.magic-value] valid-magic-values = [0, -1, 1, "", "__main__"] ``` ### Parameter\_documentation Checker ### --accept-no-param-doc *Whether to accept totally missing parameter documentation in the docstring of a function that has parameters.* **Default:** **True** ### --accept-no-raise-doc *Whether to accept totally missing raises documentation in the docstring of a function that raises an exception.* **Default:** **True** ### --accept-no-return-doc *Whether to accept totally missing return documentation in the docstring of a function that returns a statement.* **Default:** **True** ### --accept-no-yields-doc *Whether to accept totally missing yields documentation in the docstring of a generator.* **Default:** **True** ### --default-docstring-type *If the docstring type cannot be guessed the specified docstring type will be used.* **Default:** **default** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.parameter_documentation] accept-no-param-doc = true accept-no-raise-doc = true accept-no-return-doc = true accept-no-yields-doc = true # Possible choices: ['sphinx', 'epytext', 'google', 'numpy', 'default'] default-docstring-type = "default" ``` ### Typing Checker ### --runtime-typing *Set to \`\`no\`\` if the app / library does \*\*NOT\** need to support runtime introspection of type annotations. If you use type annotations **exclusively** for type checking of an application, you're probably fine. For libraries, evaluate if some users want to access the type hints at runtime first, e.g., through **typing.get\_type\_hints**. Applies to Python versions 3.7 - 3.9\* **Default:** **True** **Note:** Only **tool.pylint** is required, the section title is not. These are the default values. ``` [tool.pylint.typing] runtime-typing = true ``` ### Checkers ### Pylint features ### Pylint checkers' options and switches Pylint checkers can provide three set of features: - • options that control their execution, - • messages that they can raise, - • reports that they can generate. Below is a list of all checkers and their features. ### Async checker Verbatim name of the checker is **async**. ### Async checker Messages - **yield-inside-async-function (E1700)** *Yield inside async function* Used when an *yield* or *yield from* statement is found inside an async function. This message can't be emitted when using Python \< 3.5. - **not-async-context-manager (E1701)** *Async context manager '%s' doesn't implement \_\_aenter\_\_ and \_\_aexit\_\_.* Used when an async context manager is used with an object that does not implement the async context management protocol. This message can't be emitted when using Python \< 3.5. ### Bad-Chained-Comparison checker Verbatim name of the checker is **bad-chained-comparison**. ### Bad-Chained-Comparison checker Messages - **bad-chained-comparison (W3601)** *Suspicious %s-part chained comparison using semantically incompatible operators (%s)* Used when there is a chained comparison where one expression is part of two comparisons that belong to different semantic groups ("\<" does not mean the same thing as "is", chaining them in "0 \< x is None" is probably a mistake). ### Basic checker Verbatim name of the checker is **basic**. See also basic checker's options' documentation \<#basic-options\> ### Basic checker Messages - **init-is-generator (E0100)** *\_\_init\_\_ method is a generator* Used when the special class method \_\_init\_\_ is turned into a generator by a yield in its body. - **return-in-init (E0101)** *Explicit return in \_\_init\_\_* Used when the special class method \_\_init\_\_ has an explicit return value. - **function-redefined (E0102)** *%s already defined line %s* Used when a function / class / method is redefined. - **not-in-loop (E0103)** *%r not properly in loop* Used when break or continue keywords are used outside a loop. - **return-outside-function (E0104)** *Return outside function* Used when a "return" statement is found outside a function or method. - **yield-outside-function (E0105)** *Yield outside function* Used when a "yield" statement is found outside a function or method. - **return-arg-in-generator (E0106)** *Return with argument inside generator* Used when a "return" statement with an argument is found in a generator function or method (e.g. with some "yield" statements). This message can't be emitted when using Python \>= 3.3. - **nonexistent-operator (E0107)** *Use of the non-existent %s operator* Used when you attempt to use the C-style pre-increment or pre-decrement operator -- and ++, which doesn't exist in Python. - **duplicate-argument-name (E0108)** *Duplicate argument name %r in function definition* Duplicate argument names in function definitions are syntax errors. - **abstract-class-instantiated (E0110)** *Abstract class %r with abstract methods instantiated* Used when an abstract class with *abc.ABCMeta* as metaclass has abstract methods and is instantiated. - **bad-reversed-sequence (E0111)** *The first reversed() argument is not a sequence* Used when the first argument to reversed() builtin isn't a sequence (does not implement \_\_reversed\_\_, nor \_\_getitem\_\_ and \_\_len\_\_ - **too-many-star-expressions (E0112)** *More than one starred expression in assignment* Emitted when there are more than one starred expressions (*\*x*) in an assignment. This is a SyntaxError. - **invalid-star-assignment-target (E0113)** *Starred assignment target must be in a list or tuple* Emitted when a star expression is used as a starred assignment target. - **star-needs-assignment-target (E0114)** *Can use starred expression only in assignment target* Emitted when a star expression is not used in an assignment target. - **nonlocal-and-global (E0115)** *Name %r is nonlocal and global* Emitted when a name is both nonlocal and global. - **nonlocal-without-binding (E0117)** *nonlocal name %s found without binding* Emitted when a nonlocal variable does not have an attached name somewhere in the parent scopes - **used-prior-global-declaration (E0118)** *Name %r is used prior to global declaration* Emitted when a name is used prior a global declaration, which results in an error since Python 3.6. This message can't be emitted when using Python \< 3.6. - **misplaced-format-function (E0119)** *format function is not called on str* Emitted when format function is not called on str object. e.g doing print("value: {}").format(123) instead of print("value: {}".format(123)). This might not be what the user intended to do. - **unreachable (W0101)** *Unreachable code* Used when there is some code behind a "return" or "raise" statement, which will never be accessed. - **dangerous-default-value (W0102)** *Dangerous default value %s as argument* Used when a mutable value as list or dictionary is detected in a default value for an argument. - **pointless-statement (W0104)** *Statement seems to have no effect* Used when a statement doesn't have (or at least seems to) any effect. - **pointless-string-statement (W0105)** *String statement has no effect* Used when a string is used as a statement (which of course has no effect). This is a particular case of W0104 with its own message so you can easily disable it if you're using those strings as documentation, instead of comments. - **expression-not-assigned (W0106)** *Expression "%s" is assigned to nothing* Used when an expression that is not a function call is assigned to nothing. Probably something else was intended. - **unnecessary-pass (W0107)** *Unnecessary pass statement* Used when a "pass" statement can be removed without affecting the behaviour of the code. - **unnecessary-lambda (W0108)** *Lambda may not be necessary* Used when the body of a lambda expression is a function call on the same argument list as the lambda itself; such lambda expressions are in all but a few cases replaceable with the function being called in the body of the lambda. - **duplicate-key (W0109)** *Duplicate key %r in dictionary* Used when a dictionary expression binds the same key multiple times. - **useless-else-on-loop (W0120)** *Else clause on loop without a break statement, remove the else and de-indent all the code inside it* Loops should only have an else clause if they can exit early with a break statement, otherwise the statements under else should be on the same scope as the loop itself. - **exec-used (W0122)** *Use of exec* Raised when the 'exec' statement is used. It's dangerous to use this function for a user input, and it's also slower than actual code in general. This doesn't mean you should never use it, but you should consider alternatives first and restrict the functions available. - **eval-used (W0123)** *Use of eval* Used when you use the "eval" function, to discourage its usage. Consider using *ast.literal\_eval* for safely evaluating strings containing Python expressions from untrusted sources. - **confusing-with-statement (W0124)** *Following "as" with another context manager looks like a tuple.* Emitted when a *with* statement component returns multiple values and uses name binding with *as* only for a part of those values, as in with ctx() as a, b. This can be misleading, since it's not clear if the context manager returns a tuple or if the node without a name binding is another context manager. - **using-constant-test (W0125)** *Using a conditional statement with a constant value* Emitted when a conditional statement (If or ternary if) uses a constant value for its test. This might not be what the user intended to do. - **missing-parentheses-for-call-in-test (W0126)** *Using a conditional statement with potentially wrong function or method call due to missing parentheses* Emitted when a conditional statement (If or ternary if) seems to wrongly call a function due to missing parentheses - **self-assigning-variable (W0127)** *Assigning the same variable %r to itself* Emitted when we detect that a variable is assigned to itself - **redeclared-assigned-name (W0128)** *Redeclared variable %r in assignment* Emitted when we detect that a variable was redeclared in the same assignment. - **assert-on-string-literal (W0129)** *Assert statement has a string literal as its first argument. The assert will %s fail.* Used when an assert statement has a string literal as its first argument, which will cause the assert to always pass. - **duplicate-value (W0130)** *Duplicate value %r in set* This message is emitted when a set contains the same value two or more times. - **named-expr-without-context (W0131)** *Named expression used without context* Emitted if named expression is used to do a regular assignment outside a context like if, for, while, or a comprehension. - **pointless-exception-statement (W0133)** *Exception statement has no effect* Used when an exception is created without being assigned, raised or returned for subsequent use elsewhere. - **return-in-finally (W0134)** *'return' shadowed by the 'finally' clause.* Emitted when a 'return' statement is found in a 'finally' block. This will overwrite the return value of a function and should be avoided. - **contextmanager-generator-missing-cleanup (W0135)** *The context used in function %r will not be exited.* Used when a contextmanager is used inside a generator function and the cleanup is not handled. - **continue-in-finally (W0136)** *'continue' discouraged inside 'finally' clause* Emitted when the *continue* keyword is found inside a finally clause. This will raise a SyntaxWarning starting in Python 3.14. - **break-in-finally (W0137)** *'break' discouraged inside 'finally' clause* Emitted when the *break* keyword is found inside a finally clause. This will raise a SyntaxWarning starting in Python 3.14. - **comparison-with-callable (W0143)** *Comparing against a callable, did you omit the parenthesis?* This message is emitted when pylint detects that a comparison with a callable was made, which might suggest that some parenthesis were omitted, resulting in potential unwanted behaviour. - **lost-exception (W0150)** *%s statement in finally block may swallow exception* Used when a break or a return statement is found inside the finally clause of a try...finally block: the exceptions raised in the try clause will be silently swallowed instead of being re-raised. - **nan-comparison (W0177)** *Comparison %s should be %s* Used when an expression is compared to NaN values like numpy.NaN and float('nan'). - **assert-on-tuple (W0199)** *Assert called on a populated tuple. Did you mean 'assert x,y'?* A call of assert on a tuple will always evaluate to true if the tuple is not empty, and will always evaluate to false if it is. - **literal-comparison (R0123)** *In '%s', use '%s' when comparing constant literals not '%s' ('%s')* Used when comparing an object to a literal, which is usually what you do not want to do, since you can compare to a different literal than what was expected altogether. - **comparison-with-itself (R0124)** *Redundant comparison - %s* Used when something is compared against itself. - **comparison-of-constants (R0133)** *Comparison between constants: "%s %s %s" has a constant value* When two literals are compared with each other the result is a constant. Using the constant directly is both easier to read and more performant. Initializing 'True' and 'False' this way is not required since Python 2.3. - **invalid-name (C0103)** *%s name "%s" doesn't conform to %s* Used when the name doesn't conform to naming rules associated to its type (constant, variable, class...). - **disallowed-name (C0104)** *Disallowed name "%s"* Used when the name matches bad-names or bad-names-rgxs- (unauthorized names). - **typevar-name-incorrect-variance (C0105)** *Type variable name does not reflect variance%s* Emitted when a TypeVar name doesn't reflect its type variance. According to PEP8, it is recommended to add suffixes '\_co' and '\_contra' to the variables used to declare covariant or contravariant behaviour respectively. Invariant (default) variables do not require a suffix. The message is also emitted when invariant variables do have a suffix. - **empty-docstring (C0112)** *Empty %s docstring* Used when a module, function, class or method has an empty docstring (it would be too easy ;). - **missing-module-docstring (C0114)** *Missing module docstring* Used when a module has no docstring. Empty modules do not require a docstring. - **missing-class-docstring (C0115)** *Missing class docstring* Used when a class has no docstring. Even an empty class must have a docstring. - **missing-function-docstring (C0116)** *Missing function or method docstring* Used when a function or method has no docstring. Some special methods like \_\_init\_\_ do not require a docstring. - **singleton-comparison (C0121)** *Comparison %s should be %s* Used when an expression is compared to singleton values like True, False or None. - **unidiomatic-typecheck (C0123)** *Use isinstance() rather than type() for a typecheck.* The idiomatic way to perform an explicit typecheck in Python is to use isinstance(x, Y) rather than type(x) == Y, type(x) is Y. Though there are unusual situations where these give different results. - **typevar-double-variance (C0131)** *TypeVar cannot be both covariant and contravariant* Emitted when both the "covariant" and "contravariant" keyword arguments are set to "True" in a TypeVar. - **typevar-name-mismatch (C0132)** *TypeVar name "%s" does not match assigned variable name "%s"* Emitted when a TypeVar is assigned to a variable that does not match its name argument. ### Basic checker Reports - **RP0101** Statistics by type ### Classes checker Verbatim name of the checker is **classes**. See also classes checker's options' documentation \<#classes-options\> ### Classes checker Messages - **method-hidden (E0202)** *An attribute defined in %s line %s hides this method* Used when a class defines a method which is hidden by an instance attribute from an ancestor class or set by some client code. - **access-member-before-definition (E0203)** *Access to member %r before its definition line %s* Used when an instance member is accessed before it's actually assigned. - **no-method-argument (E0211)** *Method %r has no argument* Used when a method which should have the bound instance as first argument has no argument defined. - **no-self-argument (E0213)** *Method %r should have "self" as first argument* Used when a method has an attribute different the "self" as first argument. This is considered as an error since this is a so common convention that you shouldn't break it! - **invalid-slots-object (E0236)** *Invalid object %r in \_\_slots\_\_, must contain only non empty strings* Used when an invalid (non-string) object occurs in \_\_slots\_\_. - **assigning-non-slot (E0237)** *Assigning to attribute %r not defined in class slots* Used when assigning to an attribute not defined in the class slots. - **invalid-slots (E0238)** *Invalid \_\_slots\_\_ object* Used when an invalid \_\_slots\_\_ is found in class. Only a string, an iterable or a sequence is permitted. - **inherit-non-class (E0239)** *Inheriting %r, which is not a class.* Used when a class inherits from something which is not a class. - **inconsistent-mro (E0240)** *Inconsistent method resolution order for class %r* Used when a class has an inconsistent method resolution order. - **duplicate-bases (E0241)** *Duplicate bases for class %r* Duplicate use of base classes in derived classes raise TypeErrors. - **class-variable-slots-conflict (E0242)** *Value %r in slots conflicts with class variable* Used when a value in \_\_slots\_\_ conflicts with a class variable, property or method. - **invalid-class-object (E0243)** *Invalid assignment to '\_\_class\_\_'. Should be a class definition but got a '%s'* Used when an invalid object is assigned to a \_\_class\_\_ property. Only a class is permitted. - **invalid-enum-extension (E0244)** *Extending inherited Enum class "%s"* Used when a class tries to extend an inherited Enum class. Doing so will raise a TypeError at runtime. - **declare-non-slot (E0245)** *No such name %r in \_\_slots\_\_* Raised when a type annotation on a class is absent from the list of names in \_\_slots\_\_, and \_\_slots\_\_ does not contain a \_\_dict\_\_ entry. - **non-iterator-returned (E0301)** *\_\_iter\_\_ returns non-iterator* Used when an \_\_iter\_\_ method returns something which is not an iterable (i.e. has no *\_\_next\_\_* method) - **unexpected-special-method-signature (E0302)** *The special method %r expects %s param(s), %d %s given* Emitted when a special method was defined with an invalid number of parameters. If it has too few or too many, it might not work at all. - **invalid-length-returned (E0303)** *\_\_len\_\_ does not return non-negative integer* Used when a \_\_len\_\_ method returns something which is not a non-negative integer - **invalid-bool-returned (E0304)** *\_\_bool\_\_ does not return bool* Used when a \_\_bool\_\_ method returns something which is not a bool - **invalid-index-returned (E0305)** *\_\_index\_\_ does not return int* Used when an \_\_index\_\_ method returns something which is not an integer - **invalid-repr-returned (E0306)** *\_\_repr\_\_ does not return str* Used when a \_\_repr\_\_ method returns something which is not a string - **invalid-str-returned (E0307)** *\_\_str\_\_ does not return str* Used when a \_\_str\_\_ method returns something which is not a string - **invalid-bytes-returned (E0308)** *\_\_bytes\_\_ does not return bytes* Used when a \_\_bytes\_\_ method returns something which is not bytes - **invalid-hash-returned (E0309)** *\_\_hash\_\_ does not return int* Used when a \_\_hash\_\_ method returns something which is not an integer - **invalid-length-hint-returned (E0310)** *\_\_length\_hint\_\_ does not return non-negative integer* Used when a \_\_length\_hint\_\_ method returns something which is not a non- negative integer - **invalid-format-returned (E0311)** *\_\_format\_\_ does not return str* Used when a \_\_format\_\_ method returns something which is not a string - **invalid-getnewargs-returned (E0312)** *\_\_getnewargs\_\_ does not return a tuple* Used when a \_\_getnewargs\_\_ method returns something which is not a tuple - **invalid-getnewargs-ex-returned (E0313)** *\_\_getnewargs\_ex\_\_ does not return a tuple containing (tuple, dict)* Used when a \_\_getnewargs\_ex\_\_ method returns something which is not of the form tuple(tuple, dict) - **attribute-defined-outside-init (W0201)** *Attribute %r defined outside \_\_init\_\_* Used when an instance attribute is defined outside the \_\_init\_\_ method. - **bad-staticmethod-argument (W0211)** *Static method with %r as first argument* Used when a static method has "self" or a value specified in valid- classmethod-first-arg option or valid-metaclass-classmethod-first-arg option as first argument. - **protected-access (W0212)** *Access to a protected member %s of a client class* Used when a protected member (i.e. class member with a name beginning with an underscore) is accessed outside the class or a descendant of the class where it's defined. - **implicit-flag-alias (W0213)** *Flag member %(overlap)s shares bit positions with %(sources)s* Used when multiple integer values declared within an enum.IntFlag class share a common bit position. - **arguments-differ (W0221)** *%s %s %r method* Used when a method has a different number of arguments than in the implemented interface or in an overridden method. Extra arguments with default values are ignored. - **signature-differs (W0222)** *Signature differs from %s %r method* Used when a method signature is different than in the implemented interface or in an overridden method. - **abstract-method (W0223)** *Method %r is abstract in class %r but is not overridden in child class %r* Used when an abstract method (i.e. raise NotImplementedError) is not overridden in concrete class. - **super-init-not-called (W0231)** *\_\_init\_\_ method from base class %r is not called* Used when an ancestor class method has an \_\_init\_\_ method which is not called by a derived class. - **non-parent-init-called (W0233)** *\_\_init\_\_ method from a non direct base class %r is called* Used when an \_\_init\_\_ method is called on a class which is not in the direct ancestors for the analysed class. - **invalid-overridden-method (W0236)** *Method %r was expected to be %r, found it instead as %r* Used when we detect that a method was overridden in a way that does not match its base class which could result in potential bugs at runtime. - **arguments-renamed (W0237)** *%s %s %r method* Used when a method parameter has a different name than in the implemented interface or in an overridden method. - **unused-private-member (W0238)** *Unused private member \`%s.%s\`* Emitted when a private member of a class is defined but not used. - **overridden-final-method (W0239)** *Method %r overrides a method decorated with typing.final which is defined in class %r* Used when a method decorated with typing.final has been overridden. - **subclassed-final-class (W0240)** *Class %r is a subclass of a class decorated with typing.final: %r* Used when a class decorated with typing.final has been subclassed. - **redefined-slots-in-subclass (W0244)** *Redefined slots %r in subclass* Used when a slot is re-defined in a subclass. - **super-without-brackets (W0245)** *Super call without brackets* Used when a call to super does not have brackets and thus is not an actual call and does not work as expected. - **useless-parent-delegation (W0246)** *Useless parent or super() delegation in method %r* Used whenever we can detect that an overridden method is useless, relying on parent or super() delegation to do the same thing as another method from the MRO. - **no-classmethod-decorator (R0202)** *Consider using a decorator instead of calling classmethod* Used when a class method is defined without using the decorator syntax. - **no-staticmethod-decorator (R0203)** *Consider using a decorator instead of calling staticmethod* Used when a static method is defined without using the decorator syntax. - **useless-object-inheritance (R0205)** *Class %r inherits from object, can be safely removed from bases in python3* Used when a class inherit from object, which under python3 is implicit, hence can be safely removed from bases. - **property-with-parameters (R0206)** *Cannot have defined parameters for properties* Used when we detect that a property also has parameters, which are useless, given that properties cannot be called with additional arguments. - **bad-classmethod-argument (C0202)** *Class method %s should have %s as first argument* Used when a class method has a first argument named differently than the value specified in valid-classmethod-first-arg option (default to "cls"), recommended to easily differentiate them from regular instance methods. - **bad-mcs-method-argument (C0203)** *Metaclass method %s should have %s as first argument* Used when a metaclass method has a first argument named differently than the value specified in valid-classmethod-first-arg option (default to "cls"), recommended to easily differentiate them from regular instance methods. - **bad-mcs-classmethod-argument (C0204)** *Metaclass class method %s should have %s as first argument* Used when a metaclass class method has a first argument named differently than the value specified in valid-metaclass-classmethod-first-arg option (default to "mcs"), recommended to easily differentiate them from regular instance methods. - **single-string-used-for-slots (C0205)** *Class \_\_slots\_\_ should be a non-string iterable* Used when a class \_\_slots\_\_ is a simple string, rather than an iterable. - **method-check-failed (F0202)** *Unable to check methods signature (%s / %s)* Used when Pylint has been unable to check methods signature compatibility for an unexpected reason. Please report this kind if you don't make sense of it. ### Dataclass checker Verbatim name of the checker is **dataclass**. ### Dataclass checker Messages - **invalid-field-call (E3701)** *Invalid usage of field(), %s* The dataclasses.field() specifier should only be used as the value of an assignment within a dataclass, or within the make\_dataclass() function. ### Design checker Verbatim name of the checker is **design**. See also design checker's options' documentation \<#design-options\> ### Design checker Messages - **too-many-ancestors (R0901)** *Too many ancestors (%s/%s)* Used when class has too many parent classes, try to reduce this to get a simpler (and so easier to use) class. - **too-many-instance-attributes (R0902)** *Too many instance attributes (%s/%s)* Used when class has too many instance attributes, try to reduce this to get a simpler (and so easier to use) class. - **too-few-public-methods (R0903)** *Too few public methods (%s/%s)* Used when class has too few public methods, so be sure it's really worth it. - **too-many-public-methods (R0904)** *Too many public methods (%s/%s)* Used when class has too many public methods, try to reduce this to get a simpler (and so easier to use) class. - **too-many-return-statements (R0911)** *Too many return statements (%s/%s)* Used when a function or method has too many return statement, making it hard to follow. - **too-many-branches (R0912)** *Too many branches (%s/%s)* Used when a function or method has too many branches, making it hard to follow. - **too-many-arguments (R0913)** *Too many arguments (%s/%s)* Used when a function or method takes too many arguments. - **too-many-locals (R0914)** *Too many local variables (%s/%s)* Used when a function or method has too many local variables. - **too-many-statements (R0915)** *Too many statements (%s/%s)* Used when a function or method has too many statements. You should then split it in smaller functions / methods. - **too-many-boolean-expressions (R0916)** *Too many boolean expressions in if statement (%s/%s)* Used when an if statement contains too many boolean expressions. - **too-many-positional-arguments (R0917)** *Too many positional arguments (%s/%s)* Used when a function has too many positional arguments. ### Exceptions checker Verbatim name of the checker is **exceptions**. See also exceptions checker's options' documentation \<#exceptions-options\> ### Exceptions checker Messages - **bad-except-order (E0701)** *Bad except clauses order (%s)* Used when except clauses are not in the correct order (from the more specific to the more generic). If you don't fix the order, some exceptions may not be caught by the most specific handler. - **raising-bad-type (E0702)** *Raising %s while only classes or instances are allowed* Used when something which is neither a class nor an instance is raised (i.e. a *TypeError* will be raised). - **misplaced-bare-raise (E0704)** *The raise statement is not inside an except clause* Used when a bare raise is not used inside an except clause. This generates an error, since there are no active exceptions to be reraised. An exception to this rule is represented by a bare raise inside a finally clause, which might work, as long as an exception is raised inside the try block, but it is nevertheless a code smell that must not be relied upon. - **bad-exception-cause (E0705)** *Exception cause set to something which is not an exception, nor None* Used when using the syntax "raise ... from ...", where the exception cause is not an exception, nor None. - **raising-non-exception (E0710)** *Raising a class which doesn't inherit from BaseException* Used when a class which doesn't inherit from BaseException is raised. - **notimplemented-raised (E0711)** *NotImplemented raised - should raise NotImplementedError* Used when NotImplemented is raised instead of NotImplementedError - **catching-non-exception (E0712)** *Catching an exception which doesn't inherit from Exception: %s* Used when a class which doesn't inherit from Exception is used as an exception in an except clause. - **bare-except (W0702)** *No exception type(s) specified* A bare **except:** clause will catch **SystemExit** and **KeyboardInterrupt** exceptions, making it harder to interrupt a program with **Control-C**, and can disguise other problems. If you want to catch all exceptions that signal program errors, use **except Exception:** (bare except is equivalent to **except BaseException:**). - **duplicate-except (W0705)** *Catching previously caught exception type %s* Used when an except catches a type that was already caught by a previous handler. - **try-except-raise (W0706)** *The except handler raises immediately* Used when an except handler uses raise as its first or only operator. This is useless because it raises back the exception immediately. Remove the raise operator or the entire try-except-raise block! - **raise-missing-from (W0707)** *Consider explicitly re-raising using %s'%s from %s'* Python's exception chaining shows the traceback of the current exception, but also of the original exception. When you raise a new exception after another exception was caught it's likely that the second exception is a friendly re- wrapping of the first exception. In such cases *raise from* provides a better link between the two tracebacks in the final error. - **binary-op-exception (W0711)** *Exception to catch is the result of a binary "%s" operation* Used when the exception to catch is of the form "except A or B:". If intending to catch multiple, rewrite as "except (A, B):" - **raising-format-tuple (W0715)** *Exception arguments suggest string formatting might be intended* Used when passing multiple arguments to an exception constructor, the first of them a string literal containing what appears to be placeholders intended for formatting - **wrong-exception-operation (W0716)** *Invalid exception operation. %s* Used when an operation is done against an exception, but the operation is not valid for the exception in question. Usually emitted when having binary operations between exceptions in except handlers. - **broad-exception-caught (W0718)** *Catching too general exception %s* If you use a naked **except Exception:** clause, you might end up catching exceptions other than the ones you expect to catch. This can hide bugs or make it harder to debug programs when unrelated errors are hidden. - **broad-exception-raised (W0719)** *Raising too general exception: %s* Raising exceptions that are too generic force you to catch exceptions generically too. It will force you to use a naked **except Exception:** clause. You might then end up catching exceptions other than the ones you expect to catch. This can hide bugs or make it harder to debug programs when unrelated errors are hidden. ### Format checker Verbatim name of the checker is **format**. See also format checker's options' documentation \<#format-options\> ### Format checker Messages - **unnecessary-semicolon (W0301)** *Unnecessary semicolon* Used when a statement is ended by a semi-colon (";"), which isn't necessary (that's python, not C ;). - **bad-indentation (W0311)** *Bad indentation. Found %s %s, expected %s* Used when an unexpected number of indentation's tabulations or spaces has been found. - **line-too-long (C0301)** *Line too long (%s/%s)* Used when a line is longer than a given number of characters. - **too-many-lines (C0302)** *Too many lines in module (%s/%s)* Used when a module has too many lines, reducing its readability. - **trailing-whitespace (C0303)** *Trailing whitespace* Used when there is whitespace between the end of a line and the newline. - **missing-final-newline (C0304)** *Final newline missing* Used when the last line in a file is missing a newline. - **trailing-newlines (C0305)** *Trailing newlines* Used when there are trailing blank lines in a file. - **multiple-statements (C0321)** *More than one statement on a single line* Used when more than on statement are found on the same line. - **superfluous-parens (C0325)** *Unnecessary parens after %r keyword* Used when a single item in parentheses follows an if, for, or other keyword. - **mixed-line-endings (C0327)** *Mixed line endings LF and CRLF* Used when there are mixed (LF and CRLF) newline signs in a file. - **unexpected-line-ending-format (C0328)** *Unexpected line ending format. There is '%s' while it should be '%s'.* Used when there is different newline than expected. ### Imports checker Verbatim name of the checker is **imports**. See also imports checker's options' documentation \<#imports-options\> ### Imports checker Messages - **import-error (E0401)** *Unable to import %s* Used when pylint has been unable to import a module. - **relative-beyond-top-level (E0402)** *Attempted relative import beyond top-level package* Used when a relative import tries to access too many levels in the current package. - **wildcard-import (W0401)** *Wildcard import %s* Used when *from module import \** is detected. - **reimported (W0404)** *Reimport %r (imported line %s)* Used when a module is imported more than once. - **import-self (W0406)** *Module import itself* Used when a module is importing itself. - **preferred-module (W0407)** *Prefer importing %r instead of %r* Used when a module imported has a preferred replacement module. - **misplaced-future (W0410)** *\_\_future\_\_ import is not the first non docstring statement* Python 2.5 and greater require \_\_future\_\_ import to be the first non docstring statement in the module. - **shadowed-import (W0416)** *Shadowed %r (imported line %s)* Used when a module is aliased with a name that shadows another import. - **deprecated-module (W4901)** *Deprecated module %r* A module marked as deprecated is imported. - **cyclic-import (R0401)** *Cyclic import (%s)* Used when a cyclic import between two or more modules is detected. - **consider-using-from-import (R0402)** *Use 'from %s import %s' instead* Emitted when a submodule of a package is imported and aliased with the same name, e.g., instead of **import concurrent.futures as futures** use **from** **concurrent import futures**. - **multiple-imports (C0410)** *Multiple imports on one line (%s)* Used when import statement importing multiple modules is detected. - **wrong-import-order (C0411)** *%s should be placed before %s* Used when PEP8 import order is not respected (standard imports first, then third-party libraries, then local imports). - **ungrouped-imports (C0412)** *Imports from package %s are not grouped* Used when imports are not grouped by packages. - **wrong-import-position (C0413)** *Import "%s" should be placed at the top of the module* Used when code and imports are mixed. - **useless-import-alias (C0414)** *Import alias does not rename original package* Used when an import alias is same as original package, e.g., using import numpy as numpy instead of import numpy as np. - **import-outside-toplevel (C0415)** *Import outside toplevel (%s)* Used when an import statement is used anywhere other than the module toplevel. Move this import to the top of the file. ### Imports checker Reports - **RP0401** External dependencies - **RP0402** Modules dependencies graph ### Lambda-Expressions checker Verbatim name of the checker is **lambda-expressions**. ### Lambda-Expressions checker Messages - **unnecessary-lambda-assignment (C3001)** *Lambda expression assigned to a variable. Define a function using the "def" keyword instead.* Used when a lambda expression is assigned to variable rather than defining a standard function with the "def" keyword. - **unnecessary-direct-lambda-call (C3002)** *Lambda expression called directly. Execute the expression inline instead.* Used when a lambda expression is directly called rather than executing its contents inline. ### Logging checker Verbatim name of the checker is **logging**. See also logging checker's options' documentation \<#logging-options\> ### Logging checker Messages - **logging-unsupported-format (E1200)** *Unsupported logging format character %r (%#02x) at index %d* Used when an unsupported format character is used in a logging statement format string. - **logging-format-truncated (E1201)** *Logging format string ends in middle of conversion specifier* Used when a logging statement format string terminates before the end of a conversion specifier. - **logging-too-many-args (E1205)** *Too many arguments for logging format string* Used when a logging format string is given too many arguments. - **logging-too-few-args (E1206)** *Not enough arguments for logging format string* Used when a logging format string is given too few arguments. - **logging-not-lazy (W1201)** *Use %s formatting in logging functions* Used when a logging statement has a call form of "logging.\(format\_string % (format\_args...))". Use another type of string formatting instead. You can use % formatting but leave interpolation to the logging function by passing the parameters as arguments. If logging-fstring- interpolation is disabled then you can use fstring formatting. If logging- format-interpolation is disabled then you can use str.format. - **logging-format-interpolation (W1202)** *Use %s formatting in logging functions* Used when a logging statement has a call form of "logging.\(format\_string.format(format\_args...))". Use another type of string formatting instead. You can use % formatting but leave interpolation to the logging function by passing the parameters as arguments. If logging-fstring- interpolation is disabled then you can use fstring formatting. If logging- not-lazy is disabled then you can use % formatting as normal. - **logging-fstring-interpolation (W1203)** *Use %s formatting in logging functions* Used when a logging statement has a call form of "logging.\(f"...")".Use another type of string formatting instead. You can use % formatting but leave interpolation to the logging function by passing the parameters as arguments. If logging-format-interpolation is disabled then you can use str.format. If logging-not-lazy is disabled then you can use % formatting as normal. ### Match Statements checker Verbatim name of the checker is **match\_statements**. ### Match Statements checker Messages - **bare-name-capture-pattern (E1901)** *The name capture \`case %s\` makes the remaining patterns unreachable. Use a dotted name (for example an enum) to fix this.* Emitted when a name capture pattern is used in a match statement and there are case statements below it. - **invalid-match-args-definition (E1902)** *\`\_\_match\_args\_\_\` must be a tuple of strings.* Emitted if *\_\_match\_args\_\_* isn't a tuple of strings required for match. - **too-many-positional-sub-patterns (E1903)** *%s expects %d positional sub-patterns (given %d)* Emitted when the number of allowed positional sub-patterns exceeds the number of allowed sub-patterns specified in *\_\_match\_args\_\_*. - **multiple-class-sub-patterns (E1904)** *Multiple sub-patterns for attribute %s* Emitted when there is more than one sub-pattern for a specific attribute in a class pattern. - **match-class-bind-self (R1905)** *Use '%s() as %s' instead* Match class patterns are faster if the name binding happens for the whole pattern and any lookup for *\_\_match\_args\_\_* can be avoided. - **match-class-positional-attributes (R1906)** *Use keyword attributes instead of positional ones (%s)* Keyword attributes are more explicit and slightly faster since CPython can skip the *\_\_match\_args\_\_* lookup. ### Method Args checker Verbatim name of the checker is **method\_args**. See also method\_args checker's options' documentation \<#method-args-options\> ### Method Args checker Messages - **positional-only-arguments-expected (E3102)** *\`%s()\` got some positional-only arguments passed as keyword arguments: %s* Emitted when positional-only arguments have been passed as keyword arguments. Remove the keywords for the affected arguments in the function call. - **missing-timeout (W3101)** *Missing timeout argument for method '%s' can cause your program to hang indefinitely* Used when a method needs a 'timeout' parameter in order to avoid waiting for a long time. If no timeout is specified explicitly the default value is used. For example for 'requests' the program will never time out (i.e. hang indefinitely). ### Metrics checker Verbatim name of the checker is **metrics**. ### Metrics checker Reports - **RP0701** Raw metrics ### Miscellaneous checker Verbatim name of the checker is **miscellaneous**. See also miscellaneous checker's options' documentation \<#miscellaneous-options\> ### Miscellaneous checker Messages - **fixme (W0511)** Used when a warning note as FIXME or XXX is detected. - **use-symbolic-message-instead (I0023)** Used when a message is enabled or disabled by id. ### Modified Iteration checker Verbatim name of the checker is **modified\_iteration**. ### Modified Iteration checker Messages - **modified-iterating-dict (E4702)** *Iterated dict '%s' is being modified inside for loop body, iterate through a copy of it instead.* Emitted when items are added or removed to a dict being iterated through. Doing so raises a RuntimeError. - **modified-iterating-set (E4703)** *Iterated set '%s' is being modified inside for loop body, iterate through a copy of it instead.* Emitted when items are added or removed to a set being iterated through. Doing so raises a RuntimeError. - **modified-iterating-list (W4701)** *Iterated list '%s' is being modified inside for loop body, consider iterating through a copy of it instead.* Emitted when items are added or removed to a list being iterated through. Doing so can result in unexpected behaviour, that is why it is preferred to use a copy of the list. ### Nested Min Max checker Verbatim name of the checker is **nested\_min\_max**. ### Nested Min Max checker Messages - **nested-min-max (W3301)** *Do not use nested call of '%s'; it's possible to do '%s' instead* Nested calls **min(1, min(2, 3))** can be rewritten as **min(1, 2, 3)**. ### Newstyle checker Verbatim name of the checker is **newstyle**. ### Newstyle checker Messages - **bad-super-call (E1003)** *Bad first argument %r given to super()* Used when another argument than the current class is given as first argument of the super builtin. ### Nonascii-Checker checker Verbatim name of the checker is **nonascii-checker**. ### Nonascii-Checker checker Messages - **non-ascii-file-name (W2402)** *%s name "%s" contains a non-ASCII character.* Under python 3.5, PEP 3131 allows non-ascii identifiers, but not non-ascii file names.Since Python 3.5, even though Python supports UTF-8 files, some editors or tools don't. - **non-ascii-name (C2401)** *%s name "%s" contains a non-ASCII character, consider renaming it.* Used when the name contains at least one non-ASCII unicode character. See \ for a background why this could be bad. If your programming guideline defines that you are programming in English, then there should be no need for non ASCII characters in Python Names. If not you can simply disable this check. - **non-ascii-module-import (C2403)** *%s name "%s" contains a non-ASCII character, use an ASCII-only alias for import.* Used when the name contains at least one non-ASCII unicode character. See \ for a background why this could be bad. If your programming guideline defines that you are programming in English, then there should be no need for non ASCII characters in Python Names. If not you can simply disable this check. ### Refactoring checker Verbatim name of the checker is **refactoring**. See also refactoring checker's options' documentation \<#refactoring-options\> ### Refactoring checker Messages - **consider-merging-isinstance (R1701)** *Consider merging these isinstance calls to isinstance(%s, (%s))* Used when multiple consecutive isinstance calls can be merged into one. - **too-many-nested-blocks (R1702)** *Too many nested blocks (%s/%s)* Used when a function or a method has too many nested blocks. This makes the code less understandable and maintainable. - **simplifiable-if-statement (R1703)** *The if statement can be replaced with %s* Used when an if statement can be replaced with 'bool(test)'. - **redefined-argument-from-local (R1704)** *Redefining argument with the local name %r* Used when a local name is redefining an argument, which might suggest a potential error. This is taken in account only for a handful of name binding operations, such as for iteration, with statement assignment and exception handler assignment. - **no-else-return (R1705)** *Unnecessary "%s" after "return", %s* Used in order to highlight an unnecessary block of code following an if, or a try/except containing a return statement. As such, it will warn when it encounters an else following a chain of ifs, all of them containing a return statement. - **consider-using-ternary (R1706)** *Consider using ternary (%s)* Used when one of known pre-python 2.5 ternary syntax is used. - **trailing-comma-tuple (R1707)** *Disallow trailing comma tuple* In Python, a tuple is actually created by the comma symbol, not by the parentheses. Unfortunately, one can actually create a tuple by misplacing a trailing comma, which can lead to potential weird bugs in your code. You should always use parentheses explicitly for creating a tuple. - **stop-iteration-return (R1708)** *Do not raise StopIteration in generator, use return statement instead* According to PEP479, the raise of StopIteration to end the loop of a generator may lead to hard to find bugs. This PEP specify that raise StopIteration has to be replaced by a simple return statement - **simplify-boolean-expression (R1709)** *Boolean expression may be simplified to %s* Emitted when redundant pre-python 2.5 ternary syntax is used. - **inconsistent-return-statements (R1710)** *Either all return statements in a function should return an expression, or none of them should.* According to PEP8, if any return statement returns an expression, any return statements where no value is returned should explicitly state this as return None, and an explicit return statement should be present at the end of the function (if reachable) - **useless-return (R1711)** *Useless return at end of function or method* Emitted when a single "return" or "return None" statement is found at the end of function or method definition. This statement can safely be removed because Python will implicitly return None - **consider-swap-variables (R1712)** *Consider using tuple unpacking for swapping variables* You do not have to use a temporary variable in order to swap variables. Using "tuple unpacking" to directly swap variables makes the intention more clear. - **consider-using-join (R1713)** *Consider using str.join(sequence) for concatenating strings from an iterable* Using str.join(sequence) is faster, uses less memory and increases readability compared to for-loop iteration. - **consider-using-in (R1714)** *Consider merging these comparisons with 'in' by using '%s %sin (%s)'. Use a set instead if elements are hashable.* To check if a variable is equal to one of many values, combine the values into a set or tuple and check if the variable is contained "in" it instead of checking for equality against each of the values. This is faster and less verbose. - **consider-using-get (R1715)** *Consider using dict.get for getting values from a dict if a key is present or a default if not* Using the builtin dict.get for getting a value from a dictionary if a key is present or a default if not, is simpler and considered more idiomatic, although sometimes a bit slower - **chained-comparison (R1716)** *Simplify chained comparison between the operands* This message is emitted when pylint encounters boolean operation like "a \< b and b \< c", suggesting instead to refactor it to "a \< b \< c" - **consider-using-dict-comprehension (R1717)** *Consider using a dictionary comprehension* Emitted when we detect the creation of a dictionary using the dict() callable and a transient list. Although there is nothing syntactically wrong with this code, it is hard to read and can be simplified to a dict comprehension. Also it is faster since you don't need to create another transient list - **consider-using-set-comprehension (R1718)** *Consider using a set comprehension* Although there is nothing syntactically wrong with this code, it is hard to read and can be simplified to a set comprehension. Also it is faster since you don't need to create another transient list - **simplifiable-if-expression (R1719)** *The if expression can be replaced with %s* Used when an if expression can be replaced with 'bool(test)' or simply 'test' if the boolean cast is implicit. - **no-else-raise (R1720)** *Unnecessary "%s" after "raise", %s* Used in order to highlight an unnecessary block of code following an if, or a try/except containing a raise statement. As such, it will warn when it encounters an else following a chain of ifs, all of them containing a raise statement. - **unnecessary-comprehension (R1721)** *Unnecessary use of a comprehension, use %s instead.* Instead of using an identity comprehension, consider using the list, dict or set constructor. It is faster and simpler. - **consider-using-sys-exit (R1722)** *Consider using 'sys.exit' instead* Contrary to 'exit()' or 'quit()', 'sys.exit' does not rely on the site module being available (as the 'sys' module is always available). - **no-else-break (R1723)** *Unnecessary "%s" after "break", %s* Used in order to highlight an unnecessary block of code following an if containing a break statement. As such, it will warn when it encounters an else following a chain of ifs, all of them containing a break statement. - **no-else-continue (R1724)** *Unnecessary "%s" after "continue", %s* Used in order to highlight an unnecessary block of code following an if containing a continue statement. As such, it will warn when it encounters an else following a chain of ifs, all of them containing a continue statement. - **super-with-arguments (R1725)** *Consider using Python 3 style super() without arguments* Emitted when calling the super() builtin with the current class and instance. On Python 3 these arguments are the default and they can be omitted. - **simplifiable-condition (R1726)** *Boolean condition "%s" may be simplified to "%s"* Emitted when a boolean condition is able to be simplified. - **condition-evals-to-constant (R1727)** *Boolean condition '%s' will always evaluate to '%s'* Emitted when a boolean condition can be simplified to a constant value. - **consider-using-generator (R1728)** *Consider using a generator instead '%s(%s)'* If your container can be large using a generator will bring better performance. - **use-a-generator (R1729)** *Use a generator instead '%s(%s)'* Comprehension inside of 'any', 'all', 'max', 'min' or 'sum' is unnecessary. A generator would be sufficient and faster. - **consider-using-min-builtin (R1730)** *Consider using '%s' instead of unnecessary if block* Using the min builtin instead of a conditional improves readability and conciseness. - **consider-using-max-builtin (R1731)** *Consider using '%s' instead of unnecessary if block* Using the max builtin instead of a conditional improves readability and conciseness. - **consider-using-with (R1732)** *Consider using 'with' for resource-allocating operations* Emitted if a resource-allocating assignment or call may be replaced by a 'with' block. By using 'with' the release of the allocated resources is ensured even in the case of an exception. - **unnecessary-dict-index-lookup (R1733)** *Unnecessary dictionary index lookup, use '%s' instead* Emitted when iterating over the dictionary items (key-item pairs) and accessing the value by index lookup. The value can be accessed directly instead. - **use-list-literal (R1734)** *Consider using \[\] instead of list()* Emitted when using list() to create an empty list instead of the literal \[\]. The literal is faster as it avoids an additional function call. - **use-dict-literal (R1735)** *Consider using '%s' instead of a call to 'dict'.* Emitted when using dict() to create a dictionary instead of a literal '{ ... }'. The literal is faster as it avoids an additional function call. - **unnecessary-list-index-lookup (R1736)** *Unnecessary list index lookup, use '%s' instead* Emitted when iterating over an enumeration and accessing the value by index lookup. The value can be accessed directly instead. - **use-yield-from (R1737)** *Use 'yield from' directly instead of yielding each element one by one* Yielding directly from the iterator is faster and arguably cleaner code than yielding each element one by one in the loop. - **unnecessary-negation (C0117)** *Consider changing "%s" to "%s"* Used when a boolean expression contains an unneeded negation, e.g. when two negation operators cancel each other out. - **consider-using-enumerate (C0200)** *Consider using enumerate instead of iterating with range and len* Emitted when code that iterates with range and len is encountered. Such code can be simplified by using the enumerate builtin. - **consider-iterating-dictionary (C0201)** *Consider iterating the dictionary directly instead of calling .keys()* Emitted when the keys of a dictionary are iterated through the **.keys()** method or when **.keys()** is used for a membership check. It is enough to iterate through the dictionary itself, **for key in dictionary**. For membership checks, **if key in dictionary** is faster. - **consider-using-dict-items (C0206)** *Consider iterating with .items()* Emitted when iterating over the keys of a dictionary and accessing the value by index lookup. Both the key and value can be accessed by iterating using the .items() method of the dictionary instead. - **use-maxsplit-arg (C0207)** *Use %s instead* Emitted when accessing only the first or last element of str.split(). The first and last element can be accessed by using str.split(sep, maxsplit=1)\[0\] or str.rsplit(sep, maxsplit=1)\[-1\] instead. - **use-sequence-for-iteration (C0208)** *Use a sequence type when iterating over values* When iterating over values, sequence types (e.g., **lists**, **tuples**, **ranges**) are more efficient than **sets**. - **consider-using-f-string (C0209)** *Formatting a regular string which could be an f-string* Used when we detect a string that is being formatted with format() or % which could potentially be an f-string. The use of f-strings is preferred. Requires Python 3.6 and **py-version \>= 3.6**. - **use-implicit-booleaness-not-len (C1802)** *Do not use \`len(SEQUENCE)\` without comparison to determine if a sequence is empty* Empty sequences are considered false in a boolean context. You can either remove the call to 'len' (**if not x**) or compare the length against a scalar (**if len(x) \> 1**). - **use-implicit-booleaness-not-comparison (C1803)** *"%s" can be simplified to "%s", if it is strictly a sequence, as an empty %s is falsey* Empty sequences are considered false in a boolean context. Following this check blindly in weakly typed code base can create hard to debug issues. If the value can be something else that is falsey but not a sequence (for example **None**, an empty string, or **0**) the code will not be equivalent. - **use-implicit-booleaness-not-comparison-to-string (C1804)** *"%s" can be simplified to "%s", if it is strictly a string, as an empty string is falsey* Empty string are considered false in a boolean context. Following this check blindly in weakly typed code base can create hard to debug issues. If the value can be something else that is falsey but not a string (for example **None**, an empty sequence, or **0**) the code will not be equivalent. - **use-implicit-booleaness-not-comparison-to-zero (C1805)** *"%s" can be simplified to "%s", if it is strictly an int, as 0 is falsey* 0 is considered false in a boolean context. Following this check blindly in weakly typed code base can create hard to debug issues. If the value can be something else that is falsey but not an int (for example **None**, an empty string, or an empty sequence) the code will not be equivalent. ### Similarities checker Verbatim name of the checker is **similarities**. See also similarities checker's options' documentation \<#similarities-options\> ### Similarities checker Messages - **duplicate-code (R0801)** *Similar lines in %s files* Indicates that a set of similar lines has been detected among multiple file. This usually means that the code should be refactored to avoid this duplication. ### Similarities checker Reports - **RP0801** Duplication ### Spelling checker Verbatim name of the checker is **spelling**. See also spelling checker's options' documentation \<#spelling-options\> ### Spelling checker Messages - **wrong-spelling-in-comment (C0401)** *Wrong spelling of a word '%s' in a comment:* Used when a word in comment is not spelled correctly. - **wrong-spelling-in-docstring (C0402)** *Wrong spelling of a word '%s' in a docstring:* Used when a word in docstring is not spelled correctly. - **invalid-characters-in-docstring (C0403)** *Invalid characters %r in a docstring* Used when a word in docstring cannot be checked by enchant. ### Stdlib checker Verbatim name of the checker is **stdlib**. ### Stdlib checker Messages - **invalid-envvar-value (E1507)** *%s does not support %s type argument* Env manipulation functions support only string type arguments. See \. - **singledispatch-method (E1519)** *singledispatch decorator should not be used with methods, use singledispatchmethod instead.* singledispatch should decorate functions and not class/instance methods. Use singledispatchmethod for those cases. - **singledispatchmethod-function (E1520)** *singledispatchmethod decorator should not be used with functions, use singledispatch instead.* singledispatchmethod should decorate class/instance methods and not functions. Use singledispatch for those cases. - **bad-open-mode (W1501)** *"%s" is not a valid mode for open.* Python supports: r, w, a\[, x\] modes with b, +, and U (only with r) options. See \ - **boolean-datetime (W1502)** *Using datetime.time in a boolean context.* Using datetime.time in a boolean context can hide subtle bugs when the time they represent matches midnight UTC. This behaviour was fixed in Python 3.5. See \ for reference. This message can't be emitted when using Python \>= 3.5. - **redundant-unittest-assert (W1503)** *Redundant use of %s with constant value %r* The first argument of assertTrue and assertFalse is a condition. If a constant is passed as parameter, that condition will be always true. In this case a warning should be emitted. - **bad-thread-instantiation (W1506)** *threading.Thread needs the target function* The warning is emitted when a threading.Thread class is instantiated without the target function being passed as a kwarg or as a second argument. By default, the first parameter is the group param, not the target param. - **shallow-copy-environ (W1507)** *Using copy.copy(os.environ). Use os.environ.copy() instead.* os.environ is not a dict object but proxy object, so shallow copy has still effects on original object. See \ for reference. - **invalid-envvar-default (W1508)** *%s default type is %s. Expected str or None.* Env manipulation functions return None or str values. Supplying anything different as a default may cause bugs. See \. - **subprocess-popen-preexec-fn (W1509)** *Using preexec\_fn keyword which may be unsafe in the presence of threads* The preexec\_fn parameter is not safe to use in the presence of threads in your application. The child process could deadlock before exec is called. If you must use it, keep it trivial! Minimize the number of libraries you call into. See \ - **subprocess-run-check (W1510)** *'subprocess.run' used without explicitly defining the value for 'check'.* The **check** keyword is set to False by default. It means the process launched by **subprocess.run** can exit with a non-zero exit code and fail silently. It's better to set it explicitly to make clear what the error- handling behavior is. - **unspecified-encoding (W1514)** *Using open without explicitly specifying an encoding* It is better to specify an encoding when opening documents. Using the system default implicitly can create problems on other operating systems. See \ This message can't be emitted when using Python \>= 3.15. - **forgotten-debug-statement (W1515)** *Leaving functions creating breakpoints in production code is not recommended* Calls to breakpoint(), sys.breakpointhook() and pdb.set\_trace() should be removed from code that is not actively being debugged. - **method-cache-max-size-none (W1518)** *'lru\_cache(maxsize=None)' or 'cache' will keep all method args alive indefinitely, including 'self'* By decorating a method with lru\_cache or cache the 'self' argument will be linked to the function and therefore never garbage collected. Unless your instance will never need to be garbage collected (singleton) it is recommended to refactor code to avoid this pattern or add a maxsize to the cache. The default value for maxsize is 128. - **deprecated-method (W4902)** *Using deprecated method %s()* The method is marked as deprecated and will be removed in the future. - **deprecated-argument (W4903)** *Using deprecated argument %s of method %s()* The argument is marked as deprecated and will be removed in the future. - **deprecated-class (W4904)** *Using deprecated class %s of module %s* The class is marked as deprecated and will be removed in the future. - **deprecated-decorator (W4905)** *Using deprecated decorator %s()* The decorator is marked as deprecated and will be removed in the future. - **deprecated-attribute (W4906)** *Using deprecated attribute %r* The attribute is marked as deprecated and will be removed in the future. ### String checker Verbatim name of the checker is **string**. See also string checker's options' documentation \<#string-options\> ### String checker Messages - **bad-format-character (E1300)** *Unsupported format character %r (%#02x) at index %d* Used when an unsupported format character is used in a format string. - **truncated-format-string (E1301)** *Format string ends in middle of conversion specifier* Used when a format string terminates before the end of a conversion specifier. - **mixed-format-string (E1302)** *Mixing named and unnamed conversion specifiers in format string* Used when a format string contains both named (e.g. '%(foo)d') and unnamed (e.g. '%d') conversion specifiers. This is also used when a named conversion specifier contains \* for the minimum field width and/or precision. - **format-needs-mapping (E1303)** *Expected mapping for format string, not %s* Used when a format string that uses named conversion specifiers is used with an argument that is not a mapping. - **missing-format-string-key (E1304)** *Missing key %r in format string dictionary* Used when a format string that uses named conversion specifiers is used with a dictionary that doesn't contain all the keys required by the format string. - **too-many-format-args (E1305)** *Too many arguments for format string* Used when a format string that uses unnamed conversion specifiers is given too many arguments. - **too-few-format-args (E1306)** *Not enough arguments for format string* Used when a format string that uses unnamed conversion specifiers is given too few arguments - **bad-string-format-type (E1307)** *Argument %r does not match format type %r* Used when a type required by format string is not suitable for actual argument type - **bad-str-strip-call (E1310)** *Suspicious argument in %s.%s call* The argument to a str.{l,r,}strip call contains a duplicate character, - **bad-format-string-key (W1300)** *Format string dictionary key should be a string, not %s* Used when a format string that uses named conversion specifiers is used with a dictionary whose keys are not all strings. - **unused-format-string-key (W1301)** *Unused key %r in format string dictionary* Used when a format string that uses named conversion specifiers is used with a dictionary that contains keys not required by the format string. - **bad-format-string (W1302)** *Invalid format string* Used when a PEP 3101 format string is invalid. - **missing-format-argument-key (W1303)** *Missing keyword argument %r for format string* Used when a PEP 3101 format string that uses named fields doesn't receive one or more required keywords. - **unused-format-string-argument (W1304)** *Unused format argument %r* Used when a PEP 3101 format string that uses named fields is used with an argument that is not required by the format string. - **format-combined-specification (W1305)** *Format string contains both automatic field numbering and manual field specification* Used when a PEP 3101 format string contains both automatic field numbering (e.g. '{}') and manual field specification (e.g. '{0}'). - **missing-format-attribute (W1306)** *Missing format attribute %r in format specifier %r* Used when a PEP 3101 format string uses an attribute specifier ({0.length}), but the argument passed for formatting doesn't have that attribute. - **invalid-format-index (W1307)** *Using invalid lookup key %r in format specifier %r* Used when a PEP 3101 format string uses a lookup specifier ({a\[1\]}), but the argument passed for formatting doesn't contain or doesn't have that key as an attribute. - **duplicate-string-formatting-argument (W1308)** *Duplicate string formatting argument %r, consider passing as named argument* Used when we detect that a string formatting is repeating an argument instead of using named string arguments - **f-string-without-interpolation (W1309)** *Using an f-string that does not have any interpolated variables* Used when we detect an f-string that does not use any interpolation variables, in which case it can be either a normal string or a bug in the code. - **format-string-without-interpolation (W1310)** *Using formatting for a string that does not have any interpolated variables* Used when we detect a string that does not have any interpolation variables, in which case it can be either a normal string without formatting or a bug in the code. - **anomalous-backslash-in-string (W1401)** *Anomalous backslash in string: '%s'. String constant might be missing an r prefix.* Used when a backslash is in a literal string but not as an escape. - **anomalous-unicode-escape-in-string (W1402)** *Anomalous Unicode escape in byte string: '%s'. String constant might be missing an r or u prefix.* Used when an escape like u is encountered in a byte string where it has no effect. - **implicit-str-concat (W1404)** *Implicit string concatenation found in %s* String literals are implicitly concatenated in a literal iterable definition : maybe a comma is missing ? - **inconsistent-quotes (W1405)** *Quote delimiter %s is inconsistent with the rest of the file* Quote delimiters are not used consistently throughout a module (with allowances made for avoiding unnecessary escaping). - **redundant-u-string-prefix (W1406)** *The u prefix for strings is no longer necessary in Python \>=3.0* Used when we detect a string with a u prefix. These prefixes were necessary in Python 2 to indicate a string was Unicode, but since Python 3.0 strings are Unicode by default. ### Threading checker Verbatim name of the checker is **threading**. ### Threading checker Messages - **useless-with-lock (W2101)** *'%s()' directly created in 'with' has no effect* Used when a new lock instance is created by using with statement which has no effect. Instead, an existing instance should be used to acquire lock. ### Typecheck checker Verbatim name of the checker is **typecheck**. See also typecheck checker's options' documentation \<#typecheck-options\> ### Typecheck checker Messages - **no-member (E1101)** *%s %r has no %r member%s* Used when a variable is accessed for a nonexistent member. - **not-callable (E1102)** *%s is not callable* Used when an object being called has been inferred to a non callable object. - **assignment-from-no-return (E1111)** *Assigning result of a function call, where the function has no return* Used when an assignment is done on a function call but the inferred function doesn't return anything. - **no-value-for-parameter (E1120)** *No value for argument %s in %s call* Used when a function call passes too few arguments. - **too-many-function-args (E1121)** *Too many positional arguments for %s call* Used when a function call passes too many positional arguments. - **unexpected-keyword-arg (E1123)** *Unexpected keyword argument %r in %s call* Used when a function call passes a keyword argument that doesn't correspond to one of the function's parameter names. - **redundant-keyword-arg (E1124)** *Argument %r passed by position and keyword in %s call* Used when a function call would result in assigning multiple values to a function parameter, one value from a positional argument and one from a keyword argument. - **missing-kwoa (E1125)** *Missing mandatory keyword argument %r in %s call* Used when a function call does not pass a mandatory keyword-only argument. - **invalid-sequence-index (E1126)** *Sequence index is not an int, slice, or instance with \_\_index\_\_* Used when a sequence type is indexed with an invalid type. Valid types are ints, slices, and objects with an \_\_index\_\_ method. - **invalid-slice-index (E1127)** *Slice index is not an int, None, or instance with \_\_index\_\_* Used when a slice index is not an integer, None, or an object with an \_\_index\_\_ method. - **assignment-from-none (E1128)** *Assigning result of a function call, where the function returns None* Used when an assignment is done on a function call but the inferred function returns nothing but None. - **not-context-manager (E1129)** *Context manager '%s' doesn't implement \_\_enter\_\_ and \_\_exit\_\_.* Used when an instance in a with statement doesn't implement the context manager protocol(\_\_enter\_\_/\_\_exit\_\_). - **invalid-unary-operand-type (E1130)** Emitted when a unary operand is used on an object which does not support this type of operation. - **unsupported-binary-operation (E1131)** Emitted when a binary arithmetic operation between two operands is not supported. - **repeated-keyword (E1132)** *Got multiple values for keyword argument %r in function call* Emitted when a function call got multiple values for a keyword. - **not-an-iterable (E1133)** *Non-iterable value %s is used in an iterating context* Used when a non-iterable value is used in place where iterable is expected - **not-a-mapping (E1134)** *Non-mapping value %s is used in a mapping context* Used when a non-mapping value is used in place where mapping is expected - **unsupported-membership-test (E1135)** *Value '%s' doesn't support membership test* Emitted when an instance in membership test expression doesn't implement membership protocol (\_\_contains\_\_/\_\_iter\_\_/\_\_getitem\_\_). - **unsubscriptable-object (E1136)** *Value '%s' is unsubscriptable* Emitted when a subscripted value doesn't support subscription (i.e. doesn't define \_\_getitem\_\_ method or \_\_class\_getitem\_\_ for a class). - **unsupported-assignment-operation (E1137)** *%r does not support item assignment* Emitted when an object does not support item assignment (i.e. doesn't define \_\_setitem\_\_ method). - **unsupported-delete-operation (E1138)** *%r does not support item deletion* Emitted when an object does not support item deletion (i.e. doesn't define \_\_delitem\_\_ method). - **invalid-metaclass (E1139)** *Invalid metaclass %r used* Emitted whenever we can detect that a class is using, as a metaclass, something which might be invalid for using as a metaclass. - **dict-iter-missing-items (E1141)** *Unpacking a dictionary in iteration without calling .items()* Emitted when trying to iterate through a dict without calling .items() - **await-outside-async (E1142)** *'await' should be used within an async function* Emitted when await is used outside an async function. - **unhashable-member (E1143)** *'%s' is unhashable and can't be used as a %s in a %s* Emitted when a dict key or set member is not hashable (i.e. doesn't define \_\_hash\_\_ method). - **invalid-slice-step (E1144)** *Slice step cannot be 0* Used when a slice step is 0 and the object doesn't implement a custom \_\_getitem\_\_ method. - **async-context-manager-with-regular-with (E1145)** *Context manager '%s' is async and should be used with 'async with'.* Used when an async context manager is used with a regular 'with' statement instead of 'async with'. - **keyword-arg-before-vararg (W1113)** *Keyword argument before variable positional arguments list in the definition of %s function* When defining a keyword argument before variable positional arguments, one can end up in having multiple values passed for the aforementioned parameter in case the method is called with keyword arguments. - **arguments-out-of-order (W1114)** *Positional arguments appear to be out of order* Emitted when the caller's argument names fully match the parameter names in the function signature but do not have the same order. - **non-str-assignment-to-dunder-name (W1115)** *Non-string value assigned to \_\_name\_\_* Emitted when a non-string value is assigned to \_\_name\_\_ - **isinstance-second-argument-not-valid-type (W1116)** *Second argument of isinstance is not a type* Emitted when the second argument of an isinstance call is not a type. - **kwarg-superseded-by-positional-arg (W1117)** *%r will be included in %r since a positional-only parameter with this name already exists* Emitted when a function is called with a keyword argument that has the same name as a positional-only parameter and the function contains a keyword variadic parameter dict. - **c-extension-no-member (I1101)** *%s %r has no %r member%s, but source is unavailable. Consider adding this module to extension-pkg-allow-list if you want to perform analysis based on run-time introspection of living objects.* Used when a variable is accessed for non-existent member of C extension. Due to unavailability of source static analysis is impossible, but it may be performed by introspecting living objects in run-time. ### Unicode Checker checker Verbatim name of the checker is **unicode\_checker**. ### Unicode Checker checker Messages - **invalid-unicode-codec (E2501)** *UTF-16 and UTF-32 aren't backward compatible. Use UTF-8 instead* For compatibility use UTF-8 instead of UTF-16/UTF-32. See also \ for a history of this issue. And \ for some possible problems when using UTF-16 for instance. - **bidirectional-unicode (E2502)** *Contains control characters that can permit obfuscated code executed differently than displayed* bidirectional unicode are typically not displayed characters required to display right-to-left (RTL) script (i.e. Chinese, Japanese, Arabic, Hebrew, ...) correctly. So can you trust this code? Are you sure it displayed correctly in all editors? If you did not write it or your language is not RTL, remove the special characters, as they could be used to trick you into executing code, that does something else than what it looks like. More Information: \ \ - **invalid-character-backspace (E2510)** *Invalid unescaped character backspace, use "b" instead.* Moves the cursor back, so the character after it will overwrite the character before. - **invalid-character-carriage-return (E2511)** *Invalid unescaped character carriage-return, use "r" instead.* Moves the cursor to the start of line, subsequent characters overwrite the start of the line. - **invalid-character-sub (E2512)** *Invalid unescaped character sub, use "x1A" instead.* Ctrl+Z "End of text" on Windows. Some programs (such as type) ignore the rest of the file after it. - **invalid-character-esc (E2513)** *Invalid unescaped character esc, use "x1B" instead.* Commonly initiates escape codes which allow arbitrary control of the terminal. - **invalid-character-nul (E2514)** *Invalid unescaped character nul, use "0" instead.* Mostly end of input for python. - **invalid-character-zero-width-space (E2515)** *Invalid unescaped character zero-width-space, use "u200B" instead.* Invisible space character could hide real code execution. - **bad-file-encoding (C2503)** *PEP8 recommends UTF-8 as encoding for Python files* PEP8 recommends UTF-8 default encoding for Python files. See \ ### Unnecessary-Dunder-Call checker Verbatim name of the checker is **unnecessary-dunder-call**. ### Unnecessary-Dunder-Call checker Messages - **unnecessary-dunder-call (C2801)** *Unnecessarily calls dunder method %s. %s.* Used when a dunder method is manually called instead of using the corresponding function/method/operator. ### Unnecessary Ellipsis checker Verbatim name of the checker is **unnecessary\_ellipsis**. ### Unnecessary Ellipsis checker Messages - **unnecessary-ellipsis (W2301)** *Unnecessary ellipsis constant* Used when the ellipsis constant is encountered and can be avoided. A line of code consisting of an ellipsis is unnecessary if there is a docstring on the preceding line or if there is a statement in the same scope. ### Unsupported Version checker Verbatim name of the checker is **unsupported\_version**. ### Unsupported Version checker Messages - **using-f-string-in-unsupported-version (W2601)** *F-strings are not supported by all versions included in the py-version setting* Used when the py-version set by the user is lower than 3.6 and pylint encounters an f-string. - **using-final-decorator-in-unsupported-version (W2602)** *typing.final is not supported by all versions included in the py-version setting* Used when the py-version set by the user is lower than 3.8 and pylint encounters a **typing.final** decorator. - **using-exception-groups-in-unsupported-version (W2603)** *Exception groups are not supported by all versions included in the py-version setting* Used when the py-version set by the user is lower than 3.11 and pylint encounters **except\*** or *ExceptionGroup\`*. - **using-generic-type-syntax-in-unsupported-version (W2604)** *Generic type syntax (PEP 695) is not supported by all versions included in the py-version setting* Used when the py-version set by the user is lower than 3.12 and pylint encounters generic type syntax. - **using-assignment-expression-in-unsupported-version (W2605)** *Assignment expression is not supported by all versions included in the py-version setting* Used when the py-version set by the user is lower than 3.8 and pylint encounters an assignment expression (walrus) operator. - **using-positional-only-args-in-unsupported-version (W2606)** *Positional-only arguments are not supported by all versions included in the py-version setting* Used when the py-version set by the user is lower than 3.8 and pylint encounters positional-only arguments. ### Variables checker Verbatim name of the checker is **variables**. See also variables checker's options' documentation \<#variables-options\> ### Variables checker Messages - **used-before-assignment (E0601)** *Using variable %r before assignment* Emitted when a local variable is accessed before its assignment took place. Assignments in try blocks are assumed not to have occurred when evaluating associated except/finally blocks. Assignments in except blocks are assumed not to have occurred when evaluating statements outside the block, except when the associated try block contains a return statement. - **undefined-variable (E0602)** *Undefined variable %r* Used when an undefined variable is accessed. - **undefined-all-variable (E0603)** *Undefined variable name %r in \_\_all\_\_* Used when an undefined variable name is referenced in \_\_all\_\_. - **invalid-all-object (E0604)** *Invalid object %r in \_\_all\_\_, must contain only strings* Used when an invalid (non-string) object occurs in \_\_all\_\_. - **invalid-all-format (E0605)** *Invalid format for \_\_all\_\_, must be tuple or list* Used when \_\_all\_\_ has an invalid format. - **possibly-used-before-assignment (E0606)** *Possibly using variable %r before assignment* Emitted when a local variable is accessed before its assignment took place in both branches of an if/else switch. - **no-name-in-module (E0611)** *No name %r in module %r* Used when a name cannot be found in a module. - **unpacking-non-sequence (E0633)** *Attempting to unpack a non-sequence%s* Used when something which is not a sequence is used in an unpack assignment - **potential-index-error (E0643)** *Invalid index for iterable length* Emitted when an index used on an iterable goes beyond the length of that iterable. - **global-variable-undefined (W0601)** *Global variable %r undefined at the module level* Used when a variable is defined through the "global" statement but the variable is not defined in the module scope. - **global-variable-not-assigned (W0602)** *Using global for %r but no assignment is done* When a variable defined in the global scope is modified in an inner scope, the 'global' keyword is required in the inner scope only if there is an assignment operation done in the inner scope. - **global-statement (W0603)** *Using the global statement* Used when you use the "global" statement to update a global variable. Pylint discourages its usage. That doesn't mean you cannot use it! - **global-at-module-level (W0604)** *Using the global statement at the module level* Used when you use the "global" statement at the module level since it has no effect. - **unused-import (W0611)** *Unused %s* Used when an imported module or variable is not used. - **unused-variable (W0612)** *Unused variable %r* Used when a variable is defined but not used. - **unused-argument (W0613)** *Unused argument %r* Used when a function or method argument is not used. - **unused-wildcard-import (W0614)** *Unused import(s) %s from wildcard import of %s* Used when an imported module or variable is not used from a *'from X import* *\*'* style import. - **redefined-outer-name (W0621)** *Redefining name %r from outer scope (line %s)* Used when a variable's name hides a name defined in an outer scope or except handler. - **redefined-builtin (W0622)** *Redefining built-in %r* Used when a variable or function override a built-in. - **undefined-loop-variable (W0631)** *Using possibly undefined loop variable %r* Used when a loop variable (i.e. defined by a for loop or a list comprehension or a generator expression) is used outside the loop. - **unbalanced-tuple-unpacking (W0632)** *Possible unbalanced tuple unpacking with sequence %s: left side has %d label%s, right side has %d value%s* Used when there is an unbalanced tuple unpacking in assignment - **cell-var-from-loop (W0640)** *Cell variable %s defined in loop* A variable used in a closure is defined in a loop. This will result in all closures using the same value for the closed-over variable. - **possibly-unused-variable (W0641)** *Possibly unused variable %r* Used when a variable is defined but might not be used. The possibility comes from the fact that locals() might be used, which could consume or not the said variable - **self-cls-assignment (W0642)** *Invalid assignment to %s in method* Invalid assignment to self or cls in instance or class method respectively. - **unbalanced-dict-unpacking (W0644)** *Possible unbalanced dict unpacking with %s: left side has %d label%s, right side has %d value%s* Used when there is an unbalanced dict unpacking in assignment or for loop ### Optional checkers Pylint provides the following optional plugins: - • Deprecated Builtins checker - • Broad Try Clause checker - • Else If Used checker - • Code Style checker - • Comparison-Placement checker - • Confusing Elif checker - • Consider Refactoring Into While checker - • Consider Ternary Expression checker - • Dict-Init-Mutate checker - • Parameter Documentation checker - • Docstyle checker - • Dunder checker - • Empty-Comment checker - • Eq-Without-Hash checker - • Consider-Using-Any-Or-All checker - • Magic-Value checker - • Design checker - • No Self Use checker - • Overlap-Except checker - • Import-Private-Name checker - • Redefined-Loop-Name checker - • Multiple Types checker - • Set Membership checker - • Typing checker - • While Used checker You can activate any or all of these extensions by adding a **load-plugins** line to the **MAIN** section of your **.pylintrc**, for example: ``` load-plugins=pylint.extensions.docparams,pylint.extensions.docstyle ``` ### Broad Try Clause checker This checker is provided by **pylint.extensions.broad\_try\_clause**. Verbatim name of the checker is **broad\_try\_clause**. See also broad\_try\_clause checker's options' documentation \<#broad-try-clause-options\> ### Broad Try Clause checker Messages - **too-many-try-statements (W0717)** Try clause contains too many statements. ### Code Style checker This checker is provided by **pylint.extensions.code\_style**. Verbatim name of the checker is **code\_style**. ### Code Style checker Documentation Checkers that can improve code consistency. As such they don't necessarily provide a performance benefit and are often times opinionated. See also code\_style checker's options' documentation \<#code-style-options\> ### Code Style checker Messages - **consider-using-namedtuple-or-dataclass (R6101)** *Consider using namedtuple or dataclass for dictionary values* Emitted when dictionary values can be replaced by namedtuples or dataclass instances. - **consider-using-tuple (R6102)** *Consider using an in-place tuple instead of list* Only for style consistency! Emitted where an in-place defined **list** can be replaced by a **tuple**. Due to optimizations by CPython, there is no performance benefit from it. - **consider-using-assignment-expr (R6103)** *Use '%s' instead* Emitted when an if assignment is directly followed by an if statement and both can be combined by using an assignment expression **:=**. Requires Python 3.8 and **py-version \>= 3.8**. - **consider-using-augmented-assign (R6104)** *Use '%s' to do an augmented assign directly* Emitted when an assignment is referring to the object that it is assigning to. This can be changed to be an augmented assign. Disabled by default! - **prefer-typing-namedtuple (R6105)** *Prefer 'typing.NamedTuple' over 'collections.namedtuple'* 'typing.NamedTuple' uses the well-known 'class' keyword with type-hints for readability (it's also faster as it avoids an internal exec call). Disabled by default! - **consider-math-not-float (R6106)** *Consider %smath.%s instead of %s* Using math.inf or math.nan permits to benefit from typing and it is up to 4 times faster than a float call (after the initial import of math). This check also catches typos in float calls as a side effect. ### Comparison-Placement checker This checker is provided by **pylint.extensions.comparison\_placement**. Verbatim name of the checker is **comparison-placement**. ### Comparison-Placement checker Messages - **misplaced-comparison-constant (C2201)** *Comparison should be %s* Used when the constant is placed on the left side of a comparison. It is usually clearer in intent to place it in the right hand side of the comparison. ### Confusing Elif checker This checker is provided by **pylint.extensions.confusing\_elif**. Verbatim name of the checker is **confusing\_elif**. ### Confusing Elif checker Messages - **confusing-consecutive-elif (R5601)** *Consecutive elif with differing indentation level, consider creating a function to separate the inner elif* Used when an elif statement follows right after an indented block which itself ends with if or elif. It may not be obvious if the elif statement was willingly or mistakenly unindented. Extracting the indented if statement into a separate function might avoid confusion and prevent errors. ### Consider-Using-Any-Or-All checker This checker is provided by **pylint.extensions.for\_any\_all**. Verbatim name of the checker is **consider-using-any-or-all**. ### Consider-Using-Any-Or-All checker Messages - **consider-using-any-or-all (C0501)** *\`for\` loop could be \`%s\`* A for loop that checks for a condition and return a bool can be replaced with any or all. ### Consider Refactoring Into While checker This checker is provided by **pylint.extensions.consider\_refactoring\_into\_while\_condition**. Verbatim name of the checker is **consider\_refactoring\_into\_while**. ### Consider Refactoring Into While checker Messages - **consider-refactoring-into-while-condition (R3501)** *Consider using 'while %s' instead of 'while %s:' an 'if', and a 'break'* Emitted when *while True:* loop is used and the first statement is a break condition. The **if / break** construct can be removed if the check is inverted and moved to the **while** statement. ### Consider Ternary Expression checker This checker is provided by **pylint.extensions.consider\_ternary\_expression**. Verbatim name of the checker is **consider\_ternary\_expression**. ### Consider Ternary Expression checker Messages - **consider-ternary-expression (W0160)** *Consider rewriting as a ternary expression* Multiple assign statements spread across if/else blocks can be rewritten with a single assignment and ternary expression ### Deprecated Builtins checker This checker is provided by **pylint.extensions.bad\_builtin**. Verbatim name of the checker is **deprecated\_builtins**. ### Deprecated Builtins checker Documentation This used to be the **bad-builtin** core checker, but it was moved to an extension instead. It can be used for finding prohibited used builtins, such as **map** or **filter**, for which other alternatives exists. If you want to control for what builtins the checker should warn about, you can use the **bad-functions** option: ``` $ pylint a.py --load-plugins=pylint.extensions.bad_builtin --bad-functions=apply,reduce ... ``` See also deprecated\_builtins checker's options' documentation \<#deprecated-builtins-options\> ### Deprecated Builtins checker Messages - **bad-builtin (W0141)** *Used builtin function %s* Used when a disallowed builtin function is used (see the bad-function option). Usual disallowed functions are the ones like map, or filter , where Python offers now some cleaner alternative like list comprehension. ### Design checker This checker is provided by **pylint.extensions.mccabe**. Verbatim name of the checker is **design**. ### Design checker Documentation You can now use this plugin for finding complexity issues in your code base. Activate it through **pylint --load-plugins=pylint.extensions.mccabe**. It introduces a new warning, **too-complex**, which is emitted when a code block has a complexity higher than a preestablished value, which can be controlled through the **max-complexity** option, such as in this example: ``` $ cat a.py def f10(): """McCabe rating: 11""" myint = 2 if myint == 5: return myint elif myint == 6: return myint elif myint == 7: return myint elif myint == 8: return myint elif myint == 9: return myint elif myint == 10: if myint == 8: while True: return True elif myint == 8: with myint: return 8 else: if myint == 2: return myint return myint return myint $ pylint a.py --load-plugins=pylint.extensions.mccabe R:1: 'f10' is too complex. The McCabe rating is 11 (too-complex) $ pylint a.py --load-plugins=pylint.extensions.mccabe --max-complexity=50 $ ``` See also design checker's options' documentation \<#design-options\> ### Design checker Messages - **too-complex (R1260)** *%s is too complex. The McCabe rating is %d* Used when a method or function is too complex based on McCabe Complexity Cyclomatic ### Dict-Init-Mutate checker This checker is provided by **pylint.extensions.dict\_init\_mutate**. Verbatim name of the checker is **dict-init-mutate**. ### Dict-Init-Mutate checker Messages - **dict-init-mutate (C3401)** *Declare all known key/values when initializing the dictionary.* Dictionaries can be initialized with a single statement using dictionary literal syntax. ### Docstyle checker This checker is provided by **pylint.extensions.docstyle**. Verbatim name of the checker is **docstyle**. ### Docstyle checker Messages - **bad-docstring-quotes (C0198)** *Bad docstring quotes in %s, expected """, given %s* Used when a docstring does not have triple double quotes. - **docstring-first-line-empty (C0199)** *First line empty in %s docstring* Used when a blank line is found at the beginning of a docstring. ### Dunder checker This checker is provided by **pylint.extensions.dunder**. Verbatim name of the checker is **dunder**. See also dunder checker's options' documentation \<#dunder-options\> ### Dunder checker Messages - **bad-dunder-name (W3201)** *Bad or misspelled dunder method name %s.* Used when a dunder method is misspelled or defined with a name not within the predefined list of dunder names. ### Else If Used checker This checker is provided by **pylint.extensions.check\_elif**. Verbatim name of the checker is **else\_if\_used**. ### Else If Used checker Messages - **else-if-used (R5501)** *Consider using "elif" instead of "else" then "if" to remove one indentation level* Used when an else statement is immediately followed by an if statement and does not contain statements that would be unrelated to it. ### Empty-Comment checker This checker is provided by **pylint.extensions.empty\_comment**. Verbatim name of the checker is **empty-comment**. ### Empty-Comment checker Messages - **empty-comment (R2044)** *Line with empty comment* Used when a # symbol appears on a line not followed by an actual comment ### Eq-Without-Hash checker This checker is provided by **pylint.extensions.eq\_without\_hash**. Verbatim name of the checker is **eq-without-hash**. ### Eq-Without-Hash checker Messages - **eq-without-hash (W1641)** *Implementing \_\_eq\_\_ without also implementing \_\_hash\_\_* Used when a class implements \_\_eq\_\_ but not \_\_hash\_\_. Objects get None as their default \_\_hash\_\_ implementation if they also implement \_\_eq\_\_. ### Import-Private-Name checker This checker is provided by **pylint.extensions.private\_import**. Verbatim name of the checker is **import-private-name**. ### Import-Private-Name checker Messages - **import-private-name (C2701)** *Imported private %s (%s)* Used when a private module or object prefixed with \_ is imported. PEP8 guidance on Naming Conventions states that public attributes with leading underscores should be considered private. ### Magic-Value checker This checker is provided by **pylint.extensions.magic\_value**. Verbatim name of the checker is **magic-value**. See also magic-value checker's options' documentation \<#magic-value-options\> ### Magic-Value checker Messages - **magic-value-comparison (R2004)** *Consider using a named constant or an enum instead of '%s'.* Using named constants instead of magic values helps improve readability and maintainability of your code, try to avoid them in comparisons. ### Multiple Types checker This checker is provided by **pylint.extensions.redefined\_variable\_type**. Verbatim name of the checker is **multiple\_types**. ### Multiple Types checker Messages - **redefined-variable-type (R0204)** *Redefinition of %s type from %s to %s* Used when the type of a variable changes inside a method or a function. ### No Self Use checker This checker is provided by **pylint.extensions.no\_self\_use**. Verbatim name of the checker is **no\_self\_use**. ### No Self Use checker Messages - **no-self-use (R6301)** *Method could be a function* Used when a method doesn't use its bound instance, and so could be written as a function. ### Overlap-Except checker This checker is provided by **pylint.extensions.overlapping\_exceptions**. Verbatim name of the checker is **overlap-except**. ### Overlap-Except checker Messages - **overlapping-except (W0714)** *Overlapping exceptions (%s)* Used when exceptions in handler overlap or are identical ### Parameter Documentation checker This checker is provided by **pylint.extensions.docparams**. Verbatim name of the checker is **parameter\_documentation**. ### Parameter Documentation checker Documentation If you document the parameters of your functions, methods and constructors and their types systematically in your code this optional component might be useful for you. Sphinx style, Google style, and Numpy style are supported. (For some examples, see \ .) You can activate this checker by adding the line: ``` load-plugins=pylint.extensions.docparams ``` to the **MAIN** section of your **.pylintrc**. This checker verifies that all function, method, and constructor docstrings include documentation of the - • parameters and their types - • return value and its type - • exceptions raised and can handle docstrings in - • Sphinx style (**param**, **type**, **return**, **rtype**, **raise** / **except**): ``` def function_foo(x, y, z): '''function foo ... :param x: bla x :type x: int :param y: bla y :type y: float :param int z: bla z :return: sum :rtype: float :raises OSError: bla ''' return x + y + z ``` - • or the Google style (**Args:**, **Returns:**, **Raises:**): ``` def function_foo(x, y, z): '''function foo ... Args: x (int): bla x y (float): bla y z (int): bla z Returns: float: sum Raises: OSError: bla ''' return x + y + z ``` - • or the Numpy style (**Parameters**, **Returns**, **Raises**): ``` def function_foo(x, y, z): '''function foo ... Parameters ---------- x: int bla x y: float bla y z: int bla z Returns ------- float sum Raises ------ OSError bla ''' return x + y + z ``` You'll be notified of **missing parameter documentation** but also of **naming inconsistencies** between the signature and the documentation which often arise when parameters are renamed automatically in the code, but not in the documentation. **Note:** by default docstrings of private and magic methods are not checked. To change this behaviour (for example, to also check **\_\_init\_\_**) add **no-docstring-rgx=^(?!\_\_init\_\_$)\_** to the **BASIC** section of your **.pylintrc**. Constructor parameters can be documented in either the class docstring or the **\_\_init\_\_** docstring, but not both: ``` class ClassFoo(object): '''Sphinx style docstring foo :param float x: bla x :param y: bla y :type y: int ''' def __init__(self, x, y): pass class ClassBar(object): def __init__(self, x, y): '''Google style docstring bar Args: x (float): bla x y (int): bla y ''' pass ``` In some cases, having to document all parameters is a nuisance, for instance if many of your functions or methods just follow a **common interface**. To remove this burden, the checker accepts missing parameter documentation if one of the following phrases is found in the docstring: - • For the other parameters, see - • For the parameters, see (with arbitrary whitespace between the words). Please add a link to the docstring defining the interface, e.g. a superclass method, after "see": ``` def callback(x, y, z): '''Sphinx style docstring for callback ... :param x: bla x :type x: int For the other parameters, see :class:`MyFrameworkUsingAndDefiningCallback` ''' return x + y + z def callback(x, y, z): '''Google style docstring for callback ... Args: x (int): bla x For the other parameters, see :class:`MyFrameworkUsingAndDefiningCallback` ''' return x + y + z ``` Naming inconsistencies in existing parameter and their type documentations are still detected. See also parameter\_documentation checker's options' documentation \<#parameter-documentation-options\> ### Parameter Documentation checker Messages - **multiple-constructor-doc (W9005)** *"%s" has constructor parameters documented in class and \_\_init\_\_* Please remove parameter declarations in the class or constructor. - **missing-raises-doc (W9006)** *"%s" not documented as being raised* Please document exceptions for all raised exception types. - **redundant-returns-doc (W9008)** *Redundant returns documentation* Please remove the return/rtype documentation from this method. - **redundant-yields-doc (W9010)** *Redundant yields documentation* Please remove the yields documentation from this method. - **missing-return-doc (W9011)** *Missing return documentation* Please add documentation about what this method returns. - **missing-return-type-doc (W9012)** *Missing return type documentation* Please document the type returned by this method. - **missing-yield-doc (W9013)** *Missing yield documentation* Please add documentation about what this generator yields. - **missing-yield-type-doc (W9014)** *Missing yield type documentation* Please document the type yielded by this method. - **missing-param-doc (W9015)** *"%s" missing in parameter documentation* Please add parameter declarations for all parameters. - **missing-type-doc (W9016)** *"%s" missing in parameter type documentation* Please add parameter type declarations for all parameters. - **differing-param-doc (W9017)** *"%s" differing in parameter documentation* Please check parameter names in declarations. - **differing-type-doc (W9018)** *"%s" differing in parameter type documentation* Please check parameter names in type declarations. - **useless-param-doc (W9019)** *"%s" useless ignored parameter documentation* Please remove the ignored parameter documentation. - **useless-type-doc (W9020)** *"%s" useless ignored parameter type documentation* Please remove the ignored parameter type documentation. - **missing-any-param-doc (W9021)** *Missing any documentation in "%s"* Please add parameter and/or type documentation. ### Redefined-Loop-Name checker This checker is provided by **pylint.extensions.redefined\_loop\_name**. Verbatim name of the checker is **redefined-loop-name**. ### Redefined-Loop-Name checker Messages - **redefined-loop-name (W2901)** *Redefining %r from loop (line %s)* Used when a loop variable is overwritten in the loop body. ### Set Membership checker This checker is provided by **pylint.extensions.set\_membership**. Verbatim name of the checker is **set\_membership**. ### Set Membership checker Messages - **use-set-for-membership (R6201)** *Consider using set for membership test* Membership tests are more efficient when performed on a lookup optimized datatype like **sets**. ### Typing checker This checker is provided by **pylint.extensions.typing**. Verbatim name of the checker is **typing**. ### Typing checker Documentation Find issue specifically related to type annotations. See also typing checker's options' documentation \<#typing-options\> ### Typing checker Messages - **broken-noreturn (E6004)** *'NoReturn' inside compound types is broken in 3.7.0 / 3.7.1* **typing.NoReturn** inside compound types is broken in Python 3.7.0 and 3.7.1. If not dependent on runtime introspection, use string annotation instead. E.g. **Callable\[..., 'NoReturn'\]**. \ - **broken-collections-callable (E6005)** *'collections.abc.Callable' inside Optional and Union is broken in 3.9.0 / 3.9.1 (use 'typing.Callable' instead)* **collections.abc.Callable** inside Optional and Union is broken in Python 3.9.0 and 3.9.1. Use **typing.Callable** for these cases instead. \ - **deprecated-typing-alias (W6001)** *'%s' is deprecated, use '%s' instead* Emitted when a deprecated typing alias is used. - **consider-using-alias (R6002)** *'%s' will be deprecated with PY39, consider using '%s' instead%s* Only emitted if 'runtime-typing=no' and a deprecated typing alias is used in a type annotation context in Python 3.7 or 3.8. - **consider-alternative-union-syntax (R6003)** *Consider using alternative union syntax instead of '%s'%s* Emitted when **typing.Union** or **typing.Optional** is used instead of the shorthand union syntax. For example, **Union\[int, float\]** instead of **int \|** **float**. Using the shorthand for unions aligns with Python typing recommendations, removes the need for imports, and avoids confusion in function signatures. - **redundant-typehint-argument (R6006)** *Type \`%s\` is used more than once in union type annotation. Remove redundant typehints.* Duplicated type arguments will be skipped by *mypy* tool, therefore should be removed to avoid confusion. - **unnecessary-default-type-args (R6007)** *Type \`%s\` has unnecessary default type args. Change it to \`%s\`.* Emitted when types have default type args which can be omitted. Mainly used for *typing.Generator* and *typing.AsyncGenerator*. ### While Used checker This checker is provided by **pylint.extensions.while\_used**. Verbatim name of the checker is **while\_used**. ### While Used checker Messages - **while-used (W0149)** *Used \`while\` loop* Unbounded *while* loops can often be rewritten as bounded *for* loops. Exceptions can be made for cases such as event loops, listeners, etc. ### API You can call **Pylint**, **symilar** and **pyreverse** from another Python program thanks to their APIs: ``` from pylint import run_pylint, run_pyreverse, run_symilar run_pylint("--disable=C", "myfile.py") run_pyreverse(...) run_symilar(...) ``` ### Pylint ### As you would launch the command line You can use the **run\_pylint** function, which is the same function called by the command line (using **sys.argv**). You can supply arguments yourself: ``` from pylint import run_pylint run_pylint(argv=["--disable=line-too-long", "myfile.py"]) ``` ### Recover the result in a stream You can also use **pylint.lint.Run** directly if you want to do something that can't be done using only pylint's command line options. Here's the basic example: ``` from pylint.lint import Run Run(argv=["--disable=line-too-long", "myfile.py"]) ``` With **Run** it is possible to invoke pylint programmatically with a reporter initialized with a custom stream: ``` from io import StringIO from pylint.lint import Run from pylint.reporters.text import TextReporter pylint_output = StringIO() # Custom open stream reporter = TextReporter(pylint_output) Run(["test_file.py"], reporter=reporter, exit=False) print(pylint_output.getvalue()) # Retrieve and print the text report ``` The reporter can accept any stream object as as parameter. In this example, the stream outputs to a file: ``` from pylint.lint import Run from pylint.reporters.text import TextReporter with open("report.out", "w") as f: reporter = TextReporter(f) Run(["test_file.py"], reporter=reporter, exit=False) ``` This would be useful to capture pylint output in an open stream which can be passed onto another program. If your program expects that the files being linted might be edited between runs, you will need to clear pylint's inference cache: ``` from pylint.lint import pylinter pylinter.MANAGER.clear_cache() ``` ### How To Guides ### How to Write a Checker You can find some simple examples in the distribution (custom.py \ , custom\_raw.py \ and deprecation\_checker.py \). There are three kinds of checkers: - • Raw checkers, which analyse each module as a raw file stream. - • Token checkers, which analyse a file using the list of tokens that represent the source code in the file. - • AST checkers, which work on an AST representation of the module. The AST representation is provided by the **astroid** library. **astroid** adds additional information and methods over **ast** in the standard library, to make tree navigation and code introspection easier. ### Writing an AST Checker Let's implement a checker to make sure that all **return** nodes in a function return a unique constant. Firstly we will need to fill in some required boilerplate: ``` import astroid from astroid import nodes from typing import TYPE_CHECKING, Optional from pylint.checkers import BaseChecker if TYPE_CHECKING: from pylint.lint import PyLinter class UniqueReturnChecker(BaseChecker): name = "unique-returns" msgs = { "W0001": ( "Returns a non-unique constant.", "non-unique-returns", "All constants returned in a function should be unique.", ), } options = ( ( "ignore-ints", { "default": False, "type": "yn", "metavar": "", "help": "Allow returning non-unique integers", }, ), ) ``` So far we have defined the following required components of our checker: - • - **A name. The name is used to generate a special configuration** section for the checker, when options have been provided. - • - **A message dictionary. Each checker is being used for finding problems** in your code, the problems being displayed to the user through **messages**. The message dictionary should specify what messages the checker is going to emit. See Defining a Message for the details about defining a new message. We have also defined an optional component of the checker. The options list defines any user configurable options. It has the following format: ``` options = ( ("option-symbol", {"argparse-like-kwarg": "value"}), ) ``` - • The **option-symbol** is a unique name for the option. This is used on the command line and in config files. The hyphen is replaced by an underscore when used in the checker, similarly to how you would use **argparse.Namespace**: ``` if not self.linter.config.ignore_ints: ... ``` Next we'll track when we enter and leave a function. ``` def __init__(self, linter: Optional["PyLinter"] = None) -> None: super().__init__(linter) self._function_stack = [] def visit_functiondef(self, node: nodes.FunctionDef) -> None: self._function_stack.append([]) def leave_functiondef(self, node: nodes.FunctionDef) -> None: self._function_stack.pop() ``` In the constructor we initialise a stack to keep a list of return nodes for each function. An AST checker is a visitor, and should implement **visit\_\** or **leave\_\** methods for the nodes it's interested in. In this case we have implemented **visit\_functiondef** and **leave\_functiondef** to add a new list of return nodes for this function, and to remove the list of return nodes when we leave the function. Finally we'll implement the check. We will define a **visit\_return** function, which is called with an **.astroid.nodes.Return** node. We'll need to be able to figure out what attributes an **.astroid.nodes.Return** node has available. We can use **astroid.extract\_node** for this: ``` >>> node = astroid.extract_node("return 5") >>> node >>> help(node) >>> node.value ``` We could also construct a more complete example: ``` >>> node_a, node_b = astroid.extract_node(""" ... def test(): ... if True: ... return 5 #@ ... return 5 #@ ... """) >>> node_a.value >>> node_a.value.value 5 >>> node_a.value.value == node_b.value.value True ``` For **astroid.extract\_node**, you can use **#@** at the end of a line to choose which statements will be extracted into nodes. For more information on **astroid.extract\_node**, see the astroid documentation \. Now we know how to use the astroid node, we can implement our check. ``` def visit_return(self, node: nodes.Return) -> None: if not isinstance(node.value, nodes.Const): return for other_return in self._function_stack[-1]: if node.value.value == other_return.value.value and not ( self.linter.config.ignore_ints and node.value.pytype() == int ): self.add_message("non-unique-returns", node=node) self._function_stack[-1].append(node) ``` Once we have established that the source code has failed our check, we use **~.BaseChecker.add\_message** to emit our failure message. Finally, we need to register the checker with pylint. Add the **register** function to the top level of the file. ``` def register(linter: "PyLinter") -> None: """This required method auto registers the checker during initialization. :param linter: The linter to register the checker to. """ linter.register_checker(UniqueReturnChecker(linter)) ``` We are now ready to debug and test our checker! ### Debugging a Checker It is very simple to get to a point where we can use **pdb**. We'll need a small test case. Put the following into a Python file: ``` def test(): if True: return 5 return 5 def test2(): if True: return 1 return 5 ``` After inserting pdb into our checker and installing it, we can run pylint with only our checker: ``` $ pylint --load-plugins=my_plugin --disable=all --enable=non-unique-returns test.py (Pdb) ``` Now we can debug our checker! **Note:** **my\_plugin** refers to a module called **my\_plugin.py**. The preferred way of making this plugin available to pylint is by installing it as a package. This can be done either from a packaging index like **PyPI** or by installing it from a local source such as with **pip install**. Alternatively, the plugin module can be made available to pylint by putting this module's parent directory in your **PYTHONPATH** environment variable. If your pylint config has an **init-hook** that modifies **sys.path** to include the module's parent directory, this will also work, but only if either: - • the **init-hook** and the **load-plugins** list are both defined in a configuration file, or... - • the **init-hook** is passed as a command-line argument and the **load-plugins** list is in the configuration file So, you cannot load a custom plugin by modifying **sys.path** if you supply the **init-hook** in a configuration file, but pass the module name in via **--load-plugins** on the command line. This is because pylint loads plugins specified on command line before loading any configuration from other sources. ### Defining a Message Pylint message is defined using the following format: ``` msgs = { "E0401": ( # message id "Unable to import %s", # template of displayed message "import-error", # message symbol "Used when pylint has been unable to import a module.", # Message description { # Additional parameters: # message control support for the old names of the messages: "old_names": [("F0401", "old-import-error")] "minversion": (3, 5), # No check under this version "maxversion": (3, 7), # No check above this version }, ), ``` The message is then formatted using the **args** parameter from **add\_message** i.e. in **self.add\_message("import-error", args=module\_we\_cant\_import, node=importnode)**, the value in **module\_we\_cant\_import** say **patglib** will be interpolled and the final result will be: **Unable to import patglib** - • The **message-id** should be a 4-digit number, prefixed with a **message category**. There are multiple message categories, these being **C**, **W**, **E**, **F**, **R**, standing for **Convention**, **Warning**, **Error**, **Fatal** and **Refactoring**. The 4 digits should not conflict with existing checkers and the first 2 digits should consistent across the checker (except shared messages). It is safe to use 51-99 as the first 2 digits for custom checkers because this range is reserved for them. - • The **displayed-message** is used for displaying the message to the user, once it is emitted. - • The **message-symbol** is an alias of the message id and it can be used wherever the message id can be used. - • The **message-help** is used when calling **pylint --help-msg**. Optionally message can contain optional extra options: - • The **old\_names** option permits to change the message id or symbol of a message without breaking the message control used on the old messages by users. The option is specified as a list of tuples (**message-id**, **old-message-symbol**) e.g. **{"old\_names": \[("F0401", "old-import-error")\]}**. The symbol / msgid association must be unique so if you're changing the message id the symbol also need to change and you can generally use the **old-** prefix for that. - • The **minversion** or **maxversion** options specify minimum or maximum version of python relevant for this message. The option value is specified as tuple with major version number as first number and minor version number as second number e.g. **{"minversion": (3, 5)}** - • The **shared** option enables sharing message between multiple checkers. As mentioned previously, normally the message cannot be shared between multiple checkers. To allow having message shared between multiple checkers, the **shared** option must be set to **True**. ### Parallelize a Checker **BaseChecker** has two methods **get\_map\_data** and **reduce\_map\_data** that permit to parallelize the checks when used with the **-j** option. If a checker actually needs to reduce data it should define **get\_map\_data** as returning something different than **None** and let its **reduce\_map\_data** handle a list of the types returned by **get\_map\_data**. An example can be seen by looking at **pylint/checkers/similar.py**. ### Testing a Checker Pylint is very well suited to test driven development. You can implement the template of the checker, produce all of your test cases and check that they fail, implement the checker, then check that all of your test cases work. Pylint provides a **pylint.testutils.CheckerTestCase** to make test cases very simple. We can use the example code that we used for debugging as our test cases. ``` import astroid import my_plugin import pylint.testutils class TestUniqueReturnChecker(pylint.testutils.CheckerTestCase): CHECKER_CLASS = my_plugin.UniqueReturnChecker def test_finds_non_unique_ints(self): func_node, return_node_a, return_node_b = astroid.extract_node(""" def test(): #@ if True: return 5 #@ return 5 #@ """) self.checker.visit_functiondef(func_node) self.checker.visit_return(return_node_a) with self.assertAddsMessages( pylint.testutils.MessageTest( msg_id="non-unique-returns", node=return_node_b, ), ): self.checker.visit_return(return_node_b) def test_ignores_unique_ints(self): func_node, return_node_a, return_node_b = astroid.extract_node(""" def test(): #@ if True: return 1 #@ return 5 #@ """) with self.assertNoMessages(): self.checker.visit_functiondef(func_node) self.checker.visit_return(return_node_a) self.checker.visit_return(return_node_b) ``` Once again we are using **astroid.extract\_node** to construct our test cases. **pylint.testutils.CheckerTestCase** has created the linter and checker for us, we simply simulate a traversal of the AST tree using the nodes that we are interested in. ### How To Write a Pylint Plugin Pylint provides support for writing two types of extensions. First, there is the concept of **checkers**, which can be used for finding problems in your code. Secondly, there is also the concept of **transform plugin**, which represents a way through which the inference and the capabilities of Pylint can be enhanced and tailored to a particular module, library of framework. In general, a plugin is a module which should have a function **register**, which takes an instance of **pylint.lint.PyLinter** as input. A plugin can optionally define a function, **load\_configuration**, which takes an instance of **pylint.lint.PyLinter** as input. This function is called after Pylint loads configuration from configuration file and command line interface. This function should load additional plugin specific configuration to Pylint. So a basic hello-world plugin can be implemented as: ``` # Inside hello_plugin.py from typing import TYPE_CHECKING import astroid if TYPE_CHECKING: from pylint.lint import PyLinter def register(linter: "PyLinter") -> None: """This required method auto registers the checker during initialization. :param linter: The linter to register the checker to. """ print('Hello world') ``` We can run this plugin by placing this module in the PYTHONPATH and invoking **pylint** as: ``` $ pylint -E --load-plugins hello_plugin foo.py Hello world ``` We can extend hello-world plugin to ignore some specific names using **load\_configuration** function: ``` # Inside hello_plugin.py from typing import TYPE_CHECKING import astroid if TYPE_CHECKING: from pylint.lint import PyLinter def register(linter: "PyLinter") -> None: """This required method auto registers the checker during initialization. :param linter: The linter to register the checker to. """ print('Hello world') def load_configuration(linter): name_checker = get_checker(linter, NameChecker) # We consider as good names of variables Hello and World name_checker.config.good_names += ('Hello', 'World') # We ignore bin directory linter.config.black_list += ('bin',) ``` Depending if we need a **transform plugin** or a **checker**, this might not be enough. For the former, this is enough to declare the module as a plugin, but in the case of the latter, we need to register our checker with the linter object, by calling the following inside the **register** function: ``` linter.register_checker(OurChecker(linter)) ``` For more information on writing a checker see How to Write a Checker \<#write-a-checker\>. ### Transform plugins ### Why write a plugin? Pylint is a static analysis tool and Python is a dynamically typed language. So there will be cases where Pylint cannot analyze files properly (this problem can happen in statically typed languages also if reflection or dynamic evaluation is used). The plugins are a way to tell Pylint how to handle such cases, since only the user would know what needs to be done. They are usually operating on the AST level, by modifying or changing it in a way which can ease its understanding by Pylint. ### Example Let us run Pylint on a module from the Python source: warnings.py \ and see what happens: ``` amitdev$ pylint -E Lib/warnings.py E:297,36: Instance of 'WarningMessage' has no 'message' member (no-member) E:298,36: Instance of 'WarningMessage' has no 'filename' member (no-member) E:298,51: Instance of 'WarningMessage' has no 'lineno' member (no-member) E:298,64: Instance of 'WarningMessage' has no 'line' member (no-member) ``` Did we catch a genuine error? Let's open the code and look at **WarningMessage** class: ``` class WarningMessage(object): """Holds the result of a single showwarning() call.""" _WARNING_DETAILS = ("message", "category", "filename", "lineno", "file", "line") def __init__(self, message, category, filename, lineno, file=None, line=None): local_values = locals() for attr in self._WARNING_DETAILS: setattr(self, attr, local_values[attr]) self._category_name = category.__name__ if category else None def __str__(self): ... ``` Ah, the fields (**message**, **category** etc) are not defined statically on the class. Instead they are added using **setattr**. Pylint would have a tough time figuring this out. ### Enter Plugin We can write a transform plugin to tell Pylint how to analyze this properly. One way to fix our example with a plugin would be to transform the **WarningMessage** class, by setting the attributes so that Pylint can see them. This can be done by registering a transform function. We can transform any node in the parsed AST like Module, Class, Function etc. In our case we need to transform a class. It can be done so: ``` from typing import TYPE_CHECKING import astroid if TYPE_CHECKING: from pylint.lint import PyLinter def register(linter: "PyLinter") -> None: """This required method auto registers the checker during initialization. :param linter: The linter to register the checker to. """ pass def transform(cls): if cls.name == 'WarningMessage': import warnings for f in warnings.WarningMessage._WARNING_DETAILS: cls.locals[f] = [astroid.ClassDef(f, None)] astroid.MANAGER.register_transform(astroid.ClassDef, transform) ``` Let's go through the plugin. First, we need to register a class transform, which is done via the **register\_transform** function in **MANAGER**. It takes the node type and function as parameters. We need to change a class, so we use **astroid.ClassDef**. We also pass a **transform** function which does the actual transformation. **transform** function is simple as well. If the class is **WarningMessage** then we add the attributes to its locals (we are not bothered about type of attributes, so setting them as class will do. But we could set them to any type we want). That's it. Note: We don't need to do anything in the **register** function of the plugin since we are not modifying anything in the linter itself. Lets run Pylint with this plugin and see: ``` amitdev$ pylint -E --load-plugins warning_plugin Lib/warnings.py amitdev$ ``` All the false positives associated with **WarningMessage** are now gone. This is just an example, any code transformation can be done by plugins. See astroid/brain \ for real life examples of transform plugins. ### Technical Reference ### Startup and the Linter Class The two main classes in **pylint.lint** are **.pylint.lint.Run** and **.pylint.lint.PyLinter**. The **.pylint.lint.Run** object is responsible for starting up pylint. It does some basic checking of the given command line options to find the initial hook to run, find the config file to use, and find which plugins have been specified. It can then create the main **.pylint.lint.PyLinter** instance and initialise it with the config file and plugins that were discovered when preprocessing the command line options. Finally the **.pylint.lint.Run** object launches any child linters for parallel jobs, and starts the linting process. The **.pylint.lint.PyLinter** is responsible for coordinating the linting process. It parses the configuration and provides it for the checkers and other plugins, it handles the messages emitted by the checkers, it handles the output reporting, and it launches the checkers. ### Checkers All of the default pylint checkers exist in **pylint.checkers**. This is where most of pylint's brains exist. Most checkers are AST based and so use **astroid**. **pylint.checkers.utils** provides a large number of utility methods for dealing with **astroid**. ### Contributing to pylint The contributor guide will help you if you want to contribute to pylint itself. ### Contributing ### Finding something to do Want to contribute to pylint? There's a lot of things you can do. Here's a list of links you can check depending on what you want to do: - • Asking a question on discord \, or on github \ - • Opening an issue \ - • Making the documentation better \ - • Making the error message better \ - • Reproducing bugs and confirming that issues are valid \ - • Investigating or debugging complicated issues \ - • Designing or specifying a solution \ - • Giving your opinion on ongoing discussion \ - • Fixing bugs and crashes \ - • Fixing false positives \ - • Creating new features or fixing false negatives \ - • Reviewing pull requests \ If you are a pylint maintainer there's also: - • Triaging issues \ - • Labeling issues that do not have an actionable label yet \ - • Preparing the next patch release \ - • Checking stale pull requests status \ ### Creating a pull request Got a change for Pylint? Below are a few steps you should take to make sure your patch gets accepted: - • You must use at least Python 3.8 for development of Pylint as it gives you access to the latest **ast** parser and some pre-commit hooks do not support python 3.7. - • Install the dev dependencies, see Contributor installation \<#contributor-install\>. - • Use our test suite and write new tests, see Testing pylint \<#contributor-testing\>. - • Document your change, if it is a non-trivial one: - • A maintainer might label the issue **skip-news** if the change does not need to be in the changelog. - • Otherwise, create a news fragment with **towncrier create \.\** which will be included in the changelog. **\** can be one of the types defined in *./towncrier.toml*. If necessary you can write details or offer examples on how the new change is supposed to work. - • Generating the doc is done with **tox -e docs** - • Send a pull request from GitHub (see About pull requests \ for more insight about this topic). - • Write comprehensive commit messages and/or a good description of what the PR does. Relate your change to an issue in the tracker if such an issue exists (see Closing issues via commit messages \ of the GitHub documentation for more information on this) - • Keep the change small, separate the consensual changes from the opinionated one. - • Don't hesitate to open multiple PRs if the change requires it. If your review is so big it requires to actually plan and allocate time to review, it's more likely that it's going to go stale. - • Maintainers might have multiple 5 to 10 minutes review windows per day, Say while waiting for their teapot to boil, or for their partner to recover from their hilarious nerdy joke, but only one full hour review time per week, if at all. - • If you used multiple emails or multiple names when contributing, add your mails and preferred name in the **script/.contributors\_aliases.json** file. ### Tips for Getting Started with Pylint Development - • Read the Technical Reference \<#technical-reference\>. It gives a short walk through of the pylint codebase and will help you identify where you will need to make changes for what you are trying to implement. - • **astroid.extract\_node** is your friend. Most checkers are AST based, so you will likely need to interact with **astroid**. A short example of how to use **astroid.extract\_node** is given here \<#astroid-extract-node\>. - • When fixing a bug for a specific check, search the code for the warning message to find where the warning is raised, and therefore where the logic for that code exists. - • When adding a new checker class you can use the **get\_unused\_message\_id\_category.py** script in **./script** to get a message id that is not used by any of the other checkers. ### Building the documentation You can use the makefile in the doc directory to build the documentation: ``` $ make -C doc/ install-dependencies $ make -C doc/ html ``` We're reusing generated files for speed, use **make clean** or **tox -e docs** when you want to start from scratch. ### How to choose the target version ? Choose depending on the kind of change you're doing: - • In **patch release** (**1.2.3**), we only fix false positives and crashes. - • In **minor releases** (**1.2.0**), we add checks, remove checks, drop python interpreters past end of life, upgrade astroid minor/major versions and fix false negatives. - • In **major releases** (**1.0.0**) we change everything else (pylint options, json output, dev API...) while still trying to minimize disruption. ### Testing pylint Pylint is very well tested and has a high code coverage. New contributions are not accepted unless they include tests. ### Contributor installation ### Basic installation Pylint is developed using the git \ distributed version control system. You can clone Pylint using ``` git clone https://github.com/pylint-dev/pylint ``` Before you start testing your code, you need to install your source-code package locally. Suppose you just cloned pylint with the previous **git clone** command. To set up your environment for testing, open a terminal and run: ``` cd pylint python3 -m venv venv source venv/bin/activate pip install -r requirements_test_min.txt pip install -e . ``` This ensures your testing environment is similar to Pylint's testing environment on GitHub. **Optionally** (Because there's an auto-fix if you open a merge request): We have pre-commit hooks which should take care of the autoformatting for you before each commit. To enable it, run **pre-commit install** in the **pylint** root directory. ### Astroid installation If you're testing new changes in astroid you need to also clone astroid \ and install with an editable installation alongside pylint as follows: ``` # Suppose you're in the pylint directory git clone https://github.com/pylint-dev/astroid.git python3 -m pip install -e astroid/ ``` You're now using the local astroid in pylint and can control the version with git for example: ``` cd astroid/ git switch my-astroid-dev-branch ``` ### Launching tests ### pytest Since we use pytest to run the tests, you can also use it on its own. We do recommend using the tox command though: ``` pytest tests/ -k test_functional ``` You can use pytest directly. If you want to run tests on a specific portion of the code with pytest and your local python version: ``` python3 -m pytest ``` Everything in tests/message with coverage for the relevant code (require pytest-cov \): ``` python3 -m pytest tests/message/ --cov=pylint.message coverage html ``` Only the functional test "missing\_kwoa\_py3": ``` python3 -m pytest "tests/test_functional.py::test_functional[missing_kwoa_py3]" ``` ### tox You can also *optionally* install tox and run our tests using the tox package, as in: ``` python -m tox python -m tox -epy313 # for Python 3.13 suite only python -m tox -epylint # for running Pylint over Pylint's codebase python -m tox -eformatting # for running formatting checks over Pylint's codebase ``` It's usually a good idea to run tox with **--recreate**. This flag tells tox to re-download all dependencies before running the tests. This can be important when a new version of astroid \ or any of the other dependencies has been published: ``` python -m tox --recreate # The entire tox environment will be recreated python -m tox --recreate -e py310 # The python 3.10 tox environment will be recreated ``` To run only a specific test suite, use a pattern for the test filename (**without** the **.py** extension), as in: ``` python -m tox -e py310 -- -k test_functional python -m tox -e py310 -- -k \*func\* python -m tox --recreate -e py310 -- -k test_functional # With recreation of the environment ``` ### Primer tests Pylint also uses what we refer to as **primer** tests. These are tests that are run automatically in our Continuous Integration and check whether any changes in Pylint lead to crashes or fatal errors on the **stdlib**, and also assess a pull request's impact on the linting of a selection of external repositories by posting the diff against **pylint**'s current output as a comment. To run the primer test for the **stdlib**, which only checks for crashes and fatal errors, you can add **--primer-stdlib** to the pytest command. For example: ``` pytest -m primer_stdlib --primer-stdlib ``` To produce the output generated on Continuous Integration for the linting of external repositories, run these commands: ``` python tests/primer/__main__.py prepare --clone python tests/primer/__main__.py run --type=pr ``` To fully simulate the process on Continuous Integration, you should then checkout **main**, and then run these commands: ``` python tests/primer/__main__.py run --type=main python tests/primer/__main__.py compare ``` The list of repositories is created on the basis of three criteria: 1) projects need to use a diverse range of language features, 2) projects need to be well maintained and 3) projects should not have a codebase that is too repetitive. This guarantees a good balance between speed of our CI and finding potential bugs. You can find the latest list of repositories and any relevant code for these tests in the **tests/primer** directory. ### Writing tests Pylint uses three types of tests: unittests, functional tests and primer tests. - • unittests can be found in **pylint/tests**. Unless you're working on pylint's internal you're probably not going to have to write any. - • Global functional tests can be found in the **pylint/tests/functional**. They are mainly used to test whether Pylint emits the correct messages. - • Configuration's functional tests can be found in the **pylint/tests/config/functional**. They are used to test Pylint's configuration loading. - • Primer tests \<#primer-tests\> you can suggest a new external repository to check but there's nothing to do most of the time. ### Unittest tests Most other tests reside in the '/pylint/test' directory. These unittests can be used to test almost all functionality within Pylint. A good step before writing any new unittests is to look at some tests that test a similar functionality. This can often help write new tests. If your new test requires any additional files you can put those in the **/pylint/test/regrtest\_data** directory. This is the directory we use to store any data needed for the unittests. ### Functional tests These are located under **/pylint/test/functional** and they are formed of multiple components. First, each Python file is considered to be a test case and it should be accompanied by a **.txt** file, having the same name. The **.txt** file contains the **pylint** messages that are supposed to be emitted by the given test file. In your **.py** test file, each line for which Pylint is supposed to emit a message has to be annotated with a comment following this pattern **# \[message\_symbol\]**, as in: ``` a, b, c = 1 # [unbalanced-tuple-unpacking] ``` If multiple messages are expected on the same line, then this syntax can be used: ``` a, b, c = 1.test # [unbalanced-tuple-unpacking, no-member] ``` You can also use **# +n: \[** where **n** is an integer to deal with special cases, e.g., where the above regular syntax makes the line too long: ``` A = 5 # +1: [singleton-comparison] B = A == None # The test will look for the `singleton-comparison` message in this line ``` If you need special control over Pylint's configuration, you can also create a **.rc** file, which can set sections of Pylint's configuration. The **.rc** file can also contain a section **\[testoptions\]** to pass options for the functional test runner. The following options are currently supported: - • "min\_pyver": Minimal python version required to run the test - • "max\_pyver": Python version from which the test won't be run. If the last supported version is 3.9 this setting should be set to 3.10. - • "min\_pyver\_end\_position": Minimal python version required to check the end\_line and end\_column attributes of the message - • "requires": Packages required to be installed locally to run the test - • "except\_implementations": List of python implementations on which the test should not run - • "exclude\_platforms": List of operating systems on which the test should not run **Different output for different Python versions** Sometimes the linting result can change between Python releases. In these cases errors can be marked as conditional. Supported operators are **\<**, **\<=**, **\>** and **\>=**. ``` def some_func() -> X: # <3.14:[undefined-variable] ... # It can also be combined with offsets # +1:<3.14:[undefined-variable] def some_other_func() -> X: ... class X: ... ``` Since the output messages are different, it is necessary to add two separate files for it. First **\.314.txt**, this will include the output messages for **\>=3.14**, i.e. should be empty here. Second **\.txt**, this will be the default for all other Python versions. **Note:** This does only work if the code itself is parsable in all tested Python versions. For new syntax, use **min\_pyver** / **max\_pyver** instead. **Functional test file locations** For existing checkers, new test cases should preferably be appended to the existing test file. For new checkers, a new file **new\_checker\_message.py** should be created (Note the use of underscores). This file should then be placed in the **test/functional/n** sub-directory. Some additional notes: - • If the checker is part of an extension the test should go in **test/functional/ext/extension\_name** - • If the test is a regression test it should go in **test/r/regression** or **test/r/regression\_02**. The file name should start with **regression\_**. - • For some sub-directories, such as **test/functional/u**, there are additional sub-directories (**test/functional/u/use**). Please check if your test file should be placed in any of these directories. It should be placed there if the sub-directory name matches the word before the first underscore of your test file name. The folder structure is enforced when running the test suite, so you might be directed to put the file in a different sub-directory. **Running and updating functional tests** During development, it's sometimes helpful to run all functional tests in your current environment in order to have faster feedback. Run from Pylint root directory with: ``` python tests/test_functional.py ``` You can use all the options you would use for pytest \, for example **-k "test\_functional\[len\_checks\]"**. Furthermore, if required the .txt file with expected messages can be regenerated based on the current output by appending **--update-functional-output** to the command line: ``` python tests/test_functional.py --update-functional-output -k "test_functional[len_checks]" ``` ### Functional tests for configurations To test the different ways to configure Pylint there is also a small functional test framework for configuration files. These tests can be found in the '/pylint/test/config' directory. To create a new test create a new file with an unused name in the directory of that type of configuration file. Subsequently add a **filename.result.json** file with 'filename' being the same name as your configuration file. This file should record what the configuration should be **compared to the standard configuration**. For example, if the configuration should add a warning to the list of disabled messages and you changed the configuration for **job** to 10 instead of the default 1 the **.json** file should include: ``` "functional_append": { "disable": [["a-message-to-be-added"],] } "jobs": 10, ``` Similarly if a message should be removed you can add the following to the **.json** file: ``` "functional_remove": { "disable": [["a-message-to-be-removed"],] } ``` If a configuration is incorrect and should lead to a crash or warning being emitted you can specify this by adding a **.out** file. This file should have the following name **name\_of\_configuration\_testfile.error\_code.out**. So, if your test is called **bad\_configuration.toml** and should exit with exit code 2 the **.out** file should be named **bad\_configuration.2.out**. The content of the **.out** file should have a similar pattern as a normal Pylint output. Note that the module name should be **{abspath}** and the file name **{relpath}**. ### Profiling and performance analysis ### Performance analysis for Pylint To analyse the performance of Pylint we recommend to use the **cProfile** module from **stdlib**. Together with the **pstats** module this should give you all the tools you need to profile a Pylint run and see which functions take how long to run. The documentation for both modules can be found at cProfile \. To profile a run of Pylint over itself you can use the following code and run it from the base directory. Note that **cProfile** will create a document called **stats** that is then read by **pstats**. The human-readable output will be stored by **pstats** in **./profiler\_stats**. It will be sorted by **cumulative time**: ``` import cProfile import pstats import sys sys.argv = ["pylint", "pylint"] cProfile.run("from pylint import __main__", "stats") with open("profiler_stats", "w", encoding="utf-8") as file: stats = pstats.Stats("stats", stream=file) stats.sort_stats("cumtime") stats.print_stats() ``` You can also interact with the stats object by sorting or restricting the output. For example, to only print functions from the **pylint** module and sort by cumulative time you could use: ``` import cProfile import pstats import sys sys.argv = ["pylint", "pylint"] cProfile.run("from pylint import __main__", "stats") with open("profiler_stats", "w", encoding="utf-8") as file: stats = pstats.Stats("stats", stream=file) stats.sort_stats("cumtime") stats.print_stats("pylint/pylint") ``` Lastly, to profile a run over your own module or code you can use: ``` import cProfile import pstats import sys sys.argv = ["pylint", "your_dir/your_file"] cProfile.run("from pylint import __main__", "stats") with open("profiler_stats", "w", encoding="utf-8") as file: stats = pstats.Stats("stats", stream=file) stats.sort_stats("cumtime") stats.print_stats() ``` The documentation of the **pstats** module discusses other possibilities to interact with the profiling output. ### Performance analysis of a specific checker To analyse the performance of specific checker within Pylint we can use the human-readable output created by **pstats**. If you search in the **profiler\_stats** file for the file name of the checker you will find all functional calls from functions within the checker. Let's say we want to check the **visit\_importfrom** method of the **variables** checker: ``` ncalls tottime percall cumtime percall filename:lineno(function) 622 0.006 0.000 8.039 0.013 /MY_PROGRAMMING_DIR/pylint/pylint/checkers/variables.py:1445(visit_importfrom) ``` The previous line tells us that this method was called 622 times during the profile and we were inside the function itself for 6 ms in total. The time per call is less than a millisecond (0.006 / 622) and thus is displayed as being 0. Often you are more interested in the cumulative time (per call). This refers to the time spent within the function and any of the functions it called or the functions they called (etc.). In our example, the **visit\_importfrom** method and all of its child-functions took a little over 8 seconds to execute, with an execution time of 0.013 ms per call. You can also search the **profiler\_stats** for an individual function you want to check. For example **\_analyse\_fallback\_blocks**, a function called by **visit\_importfrom** in the **variables** checker. This allows more detailed analysis of specific functions: ``` ncalls tottime percall cumtime percall filename:lineno(function) 1 0.000 0.000 0.000 0.000 /MY_PROGRAMMING_DIR/pylint/pylint/checkers/variables.py:1511(_analyse_fallback_blocks) ``` ### Parsing the profiler stats with other tools Often you might want to create a visual representation of your profiling stats. A good tool to do this is gprof2dot \. This tool can create a **.dot** file from the profiling stats created by **cProfile** and **pstats**. You can then convert the **.dot** file to a **.png** file with one of the many converters found online. You can read the gprof2dot \ documentation for installation instructions for your specific environment. Another option would be snakeviz \. ### OSS-Fuzz integration ### Platform overview OSS-Fuzz \ is Google's free fuzzing platform for open source software. It runs astroid's fuzz targets to help detect reliability issues that could affect astroid and Pylint. Google provides public build logs \ and fuzzing stats \, but most of the details about bug reports and fuzzed testcases require approved access. ### Gaining access The configuration files for the OSS-Fuzz integration can be found in the OSS-Fuzz repository \. The **project.yaml** file controls who has access to bug reports and testcases. Ping the maintainers if you'd like to be added to the list (note: a Google account is required for access). ### Fuzzing progress Once you have access to OSS-Fuzz, you can log in to \ with your Google account to see a dashboard of astroid's fuzzing progress. ### Testcases The dashboard contains a link to a testcases page \ that lists all testcases that currently trigger a bug in astroid. Every testcase has a dedicated page with links to view and download a minimized testcase for reproducing the failure. Each testcase page also contains a stacktrace for the failure and stats about how often the failure is encountered while fuzzing. ### Reproducing a failure You can download a minimized testcase and run it locally to debug a failure on your machine. For example, to reproduce a failure with the **fuzz\_parse** fuzz target, you can run the following commands: ``` mkdir fuzzing-repro cd fuzzing-repro # Note: Atheris doesn't support Python 3.12+ yet: # https://github.com/google/atheris/issues/82 uv venv --python 3.11 source .venv/bin/activate git clone https://github.com/pylint-dev/astroid.git cd astroid uv pip install atheris==2.3.0 uv pip install --editable . # Save the minimized testcase as `minimized.py` in the astroid directory cat << EOF > ./run_fuzz_parse.py import astroid import atheris with open('minimized.py', 'rb') as f: fdp = atheris.FuzzedDataProvider(f.read()) code = fdp.ConsumeUnicodeNoSurrogates(fdp.ConsumeIntInRange(0, 4096)) astroid.builder.parse(code) EOF python ./run_fuzz_parse.py ``` If the failure does not reproduce locally, you can try reproducing the issue in an OSS-Fuzz container: ``` git clone https://github.com/google/oss-fuzz.git cd oss-fuzz python infra/helper.py build_image astroid python infra/helper.py build_fuzzers astroid python infra/helper.py reproduce astroid fuzz_parse minimized.py ``` Some failures may only be reproducible in an OSS-Fuzz container because of differences in Python versions between the OSS-Fuzz platform and your local environment. ### Code coverage The dashboard also links to code coverage data for individual fuzz targets and combined code coverage data for all targets (click on the "TOTAL COVERAGE" link for the combined data). The combined coverage data is helpful for identifying coverage gaps, insufficient corpus data, and potential candidates for future fuzz targets. ### Bug reports Bug reports for new failures are automatically filed in the OSS-Fuzz bug tracker with an astroid label \. Make sure you are logged in to view all existing issues. ### Build maintenance Google runs compiled fuzz targets on Google Compute Engine VMs. This architecture requires each project to provide a **Dockerfile** and **build.sh** script to download code, configure dependencies, compile fuzz targets, and package any corpus files. astroid's build files and fuzz-target code can be found in the OSS-Fuzz repo \. If dependencies change or if new fuzz targets are added, then you may need to modify the build files and build a new Docker image for OSS-Fuzz. ### Building an image Run the following commands to build astroid's OSS-Fuzz image and fuzz targets: ``` git clone https://github.com/google/oss-fuzz.git cd oss-fuzz python infra/helper.py build_image astroid python infra/helper.py build_fuzzers astroid ``` Any changes you make to the build files must be submitted as pull requests to the OSS-Fuzz repo. ### Debugging build failures You can debug build failures during the **build\_fuzzers** stage by creating a container and manually running the **compile** command: ``` # Create a container for building fuzz targets python infra/helper.py shell astroid # Run this command inside the container to build the fuzz targets compile ``` The **build.sh** script will be located at **/src/build.sh** inside the container. ### Quick links - • OSS-Fuzz dashboard \ - • OSS-Fuzz configuration files, build scripts, and fuzz targets for astroid \ - • All open OSS-Fuzz bugs for astroid \ - • Google's OSS-Fuzz documentation \ ### Releasing a pylint version So, you want to release the **X.Y.Z** version of pylint ? ### Releasing a major or minor version **Before releasing a major or minor version check if there are any** **unreleased commits on the maintenance branch. If so, release a last** **patch release first. See \`\`Releasing a patch version\`\`.** - • Write the **Summary -- Release highlights** in **doc/whatsnew** and upgrade the release date. - • Install the release dependencies: **pip3 install -r requirements\_test.txt**. This pins the exact **astroid** version used by the CI (see **requirements\_test\_min.txt**). Make sure this pinned version is the one installed before running **tbump**: a different **astroid** produces different functional test output, which then gets committed into the release and breaks the CI. - • Bump the version and release by using **tbump X.Y.0 --no-push --no-tag**. (For example: **tbump 2.4.0 --no-push --no-tag**) - • Check the commit created with **git show** amend the commit if required. - • Move the **main** branch up to a dev version with **tbump**: ``` tbump X.Y+1.0-dev0 --no-tag --no-push # You can interrupt after the first step git commit -am "Upgrade the version to x.y+1.0-dev0 following x.y.0 release" ``` For example: ``` tbump 2.5.0-dev0 --no-tag --no-push git commit -am "Upgrade the version to 2.5.0-dev0 following 2.4.0 release" ``` - • tbump will have created a new **What's new in Pylint X.Y+1** document. Add it to **doc/whatsnew/3/index.rst**. Take a look at the examples from **doc/whatsnew**. Commit that with **git commit -a --amend**. - • Push to a release branch - • Open a merge request with the two commits (no one can push directly on **main**) - • After the merge, recover the merged commits on **main** and tag the first one (the version should be **X.Y.Z**) as **vX.Y.Z** (For example: **v2.4.0**) - • Push the tag. - • Release the version on GitHub with the same name as the tag and copy and paste the appropriate changelog in the description. This triggers the PyPI release. - • Create a **maintenance/X.Y.x** (For example: **maintenance/2.4.x** from the **v2.4.0** tag.) - • Upgrade the pattern for the protected branches in the settings under **Branches** / **Branch protection rules**. (For example: **maintenance/2.4\*** instead of **maintenance/2.3\***.). There’s a lot of configuration done in these settings, do NOT recreate it from scratch. - • Delete the **maintenance/X.Y-1.x** branch. (For example: **maintenance/2.3.x**) - • Select all the *closed* issues labelled **backport maintenance/X.Y-1.x** and label them **backported**, then rename the **backport maintenance/X.Y-1.x** label to **backport maintenance/X.Y.x** (for example rename **backport maintenance/2.3.x** to **backport maintenance/2.4.x**) - • Close the current milestone and create the new ones (For example: close **2.4.0**, create **2.4.1** and **2.6.0**) - • Hide and deactivate all the patch releases for the previous minor release on readthedocs \, except the last one. (For example: hide **v2.4.0**, **v2.4.1**, **v2.4.2** and keep only **v2.4.3**) ### Back-porting a fix from main to the maintenance branch Whenever a PR on **main** should be released in a patch release on the current maintenance branch: - • Label the PR with **backport maintenance/X.Y-1.x**. (For example **backport maintenance/2.3.x**) - • Squash the PR before merging (alternatively rebase if there’s a single commit) - • (If the automated cherry-pick has conflicts) - • Add a **Needs backport** label and do it manually. - • You might alternatively also: - • Cherry-pick the changes that create the conflict if it’s not a new feature before doing the original PR cherry-pick manually. - • Decide to wait for the next minor to release the PR - • In any case upgrade the milestones in the original PR and newly cherry-picked PR to match reality. - • Release a patch version ### Releasing a patch version We release patch versions when a crash or a bug is fixed on the main branch and has been cherry-picked on the maintenance branch. - • Install the release dependencies: **pip3 install -r requirements\_test.txt**. This pins the exact **astroid** version used by the CI (see **requirements\_test\_min.txt**). Make sure this pinned version is the one installed before running **tbump**: a different **astroid** produces different functional test output, which then gets committed into the release and breaks the CI. - • Bump the version and release by using **tbump X.Y-1.Z --no-push**. (For example: **tbump 2.3.5 --no-push**) - • Check the result visually with **git show**. - • Open a merge request of **release-X.Y-1.Z'** in **maintenance/X.Y.x** (For example: **release-2.3.5-branch** in **maintenance/2.3.x**) to run the CI tests for this branch. - • Create and push the tag. - • Release the version on GitHub with the same name as the tag and copy and paste the changelog from the ReadtheDoc generated documentation from the pull request pipeline in the description. This triggers the PyPI release. - • Merge the **maintenance/X.Y.x** branch on the main branch. The main branch should have the changelog for **X.Y-1.Z+1** (For example **v2.3.6**). This merge is required so **pre-commit autoupdate** works for pylint. - • Fix version conflicts properly, or bump the version to **X.Y.0-devZ** (For example: **2.4.0-dev6**) before pushing on the main branch - • Close the current milestone and create the new one (For example: close **2.3.5**, create **2.3.6**) ### Milestone handling We move issues that were not done to the next milestone and block releases only if there are any open issues labelled as **blocker**. ### Governance ### How to become part of the project ? ### How to become a contributor ? - • Follow the code of conduct - • Search by yourself before asking for help - • Open an issue - • Investigate an issue and report your finding - • Open a merge request directly if you feel it's a consensual change Reporting a bug is being a contributor already. ### How to become a triager ? - • Create a pylint plugin, then migrate it to the 'pylint-dev' github organization. Or: - • Contribute for more than 3 releases consistently. - • Do not be too opinionated, follow the code of conduct without requiring emotional works from the maintainers. It does not mean that disagreements are impossible, only that arguments should stay technical and reasonable so the conversation is civil and productive. - • Have a maintainer suggest that you become triager, without you asking - • Get unanimous approval or neutral agreement from current maintainers. ### How to become a maintainer ? - • Take ownership of a part of the code that is not maintained well at the moment or that you contributed personally (if we feel we can't merge something without your review, you're going to be able to merge those yourself soon). Or: - • Contribute two big code merge requests over multiple releases (for example one checker in 2.13 and the following bug after release and one complicated bug fixes in 2.14). Otherwise contributing for more than 3 releases consistently with great technical and interpersonal skills. - • Triage for multiple months (close duplicate, clean up issues, answer questions...) - • Have an admin suggest that you become maintainer, without you asking - • Get unanimous approval or neutral agreement from current maintainers. ### How to become an admin ? - • Contribute for several hundreds of commits over a long period of time with excellent interpersonal skills and code quality. - • Maintain pylint for multiple years (code review, triaging and maintenance tasks). - • At this point probably have another admin leave the project or become inactive for years. - • Have an admin suggest that you become an admin, without you asking. - • Get unanimous approval or neutral agreement from current admins. ### How are decisions made ? Everyone is expected to follow the code of conduct. pylint is a do-ocracy / democracy. You're not allowed to behave poorly because you contributed a lot. But if you're not going to do the future maintenance work, your valid opinions might not be taken into account by those that will be affected by it. ### What are the fundamental tenets of pylint development? General: - • We favor correctness over performance, because pylint is not used primarily for its performance. Performance is still important and needs to be taken into account from the get go. - • We then favor false negatives over false positives if correctness is impossible to achieve. - • We try to keep the configuration sane, but if there's a hard decision to take we add an option so that pylint is multiple sizes fit all (after configuration) Where to add a new checker or message: - • Error messages (things that will result in an error if run) should be builtin checks, activated by default - • Messages that are opinionated, even slightly, should be opt-in (added as an extension \<#plugins\>) - • We don't shy away from opinionated checks (like the while checker), but there's such a thing as too opinionated, if something is too opinionated it should be an external pylint plugin \<#plugins\>. ### How are disagreements handled ? When something is not consensual users, maintainers, and admins discuss until an agreement is reached. Depending on the difficulty of the discussion and the importance of a fast resolution, a decision can be taken: - • Unanimously between discussion participants, contributors and maintainers (preferably) - • By asking discussion participants for their opinions with an emoji survey in the issue and then using the majority if no maintainers feel strongly about the issue. - • By majority of admins if no admins feel strongly about the issue. - • By asking all users for their opinions in a new issue that will be pinned for multiple months before taking the decision if two admins feel strongly on an opposite side of the issue. Once the result is obvious the majority decision is not up for discussion anymore. ### Pyreverse **pyreverse** is a powerful tool that creates UML diagrams from your Python code. It helps you visualize: - • Package dependencies and structure - • Class hierarchies and relationships - • Method and attribute organization ### Output Formats **pyreverse** supports multiple output formats: - • - **Native formats:** - • **.dot**/**.gv** (Graphviz) - • **.puml**/**.plantuml** (PlantUML) - • **.mmd**/**.html** (MermaidJS) - • - **Additional formats (requires Graphviz installation):** - • All Graphviz output formats \ (PNG, SVG, PDF, etc.) - • **pyreverse** first generates a temporary **.gv** file, which is then fed to Graphviz to generate the final image ### Getting Started Check out the Usage \<\> guide to learn about available options, or see Example Output \<\> for sample diagrams and common use cases. ### Usage **pyreverse** is run from the command line using the following syntax: ``` pyreverse [options] ``` where **\** is one or more Python packages or modules to analyze. The available options are organized into the following categories: - • Filtering and Scope - Control which classes and relationships appear in your diagrams - • Display Options - Customize the visual appearance including colors and labels - • Output Control - Select output formats and set the destination directory - • Project Configuration - Define project settings like source roots and ignored files ### Filtering and Scope ### --all-ancestors *Show all ancestors of all classes in \.* **Default:** **None** ### --all-associated *Show all classes associated with the target classes, including indirect associations.* **Default:** **None** ### --class *Create a class diagram with all classes related to \; this uses by default the options -ASmy* **Default:** **None** ### --filter-mode *Filter attributes and functions according to \. Correct modes are:* *'PUB\_ONLY' filter all non public attributes \[DEFAULT\], equivalent to PRIVATE+SPECIAL* *'ALL' no filter* *'SPECIAL' filter Python special functions except constructor* *'OTHER' filter protected and private attributes* **Default:** **PUB\_ONLY** ### --max-depth *Maximum depth of packages/modules to include in the diagram, relative to the deepest specified package. A depth of 0 shows only the specified packages/modules, while 1 includes their immediate children, etc. When specifying nested packages, depth is calculated from the deepest package level. If not specified, all packages/modules in the hierarchy are shown.* **Default:** **None** ### --show-ancestors *Show \ generations of ancestor classes not in \.* **Default:** **None** ### --show-associated *Show \ levels of associated classes not in \.* **Default:** **None** ### --show-builtin *Include builtin objects in representation of classes.* **Default:** **False** ### --show-stdlib *Include standard library objects in representation of classes.* **Default:** **False** ### Display Options ### --color-palette *Comma separated list of colors to use for the package depth coloring.* **Default:** **('#77AADD', '#99DDFF', '#44BB99', '#BBCC33', '#AAAA00', '#EEDD88', '#EE8866', '#FFAABB', '#DDDDDD')** ### --colorized *Use colored output. Classes/modules of the same package get the same color.* **Default:** **False** ### --max-color-depth *Use separate colors up to package depth of \. Higher depths will reuse colors.* **Default:** **2** ### --module-names *Include module name in the representation of classes.* **Default:** **None** ### --no-standalone *Only show nodes with connections.* **Default:** **False** ### --only-classnames *Don't show attributes and methods in the class boxes; this disables -f values.* **Default:** **False** ### Output Control ### --output *Create a \*.\ output file if format is available. Available formats are: .dot, .puml, .plantuml, .mmd, .html. Any other format will be tried to be created by using the 'dot' command line tool, which requires a graphviz installation. In this case, these additional formats are available (see \`Graphviz output formats \\`\_).* **Default:** **dot** ### --output-directory *Set the output directory path.* **Default:** **""** ### Project Configuration ### --ignore *Files or directories to be skipped. They should be base names, not paths.* **Default:** **('CVS',)** ### --project *Set the project name. This will later be appended to the output file names.* **Default:** **""** ### --source-roots *Add paths to the list of the source roots. Supports globbing patterns. The source root is an absolute path or a path relative to the current working directory used to determine a package namespace for modules located under the source root.* **Default:** **()** ### --verbose *Makes pyreverse more verbose/talkative. Mostly useful for debugging.* **Default:** **False** ### Example Output Example diagrams generated with the **.puml** output format are shown below. ### Package Diagram \[image: Package diagram generated by pyreverse\] \[image\] ### Class Diagram \[image: Class diagram generated by pyreverse\] \[image\] ### Creating Class Diagrams for Specific Classes In many cases creating a single diagram depicting all classes in the project yields a rather unwieldy, giant diagram. While limiting the input path to a single package or module can already help greatly to narrow down the scope, the **-c** option provides another way to create a class diagram focusing on a single class and its collaborators. For example, running: ``` pyreverse -ASmy -c pylint.checkers.classes.ClassChecker pylint ``` will generate the full class and package diagrams for **pylint**, but will additionally generate a file **pylint.checkers.classes.ClassChecker.dot**: \[image: Package diagram generated by pyreverse\] \[image\] ### Symilar The console script **symilar** finds copy pasted block of text in a set of files. It provides a command line interface to check only the **duplicate-code** message. It can be invoked with: ``` symilar [-d|--duplicates min_duplicated_lines] [-i|--ignore-comments] [--ignore-docstrings] [--ignore-imports] [--ignore-signatures] file1... ``` All files that shall be checked have to be passed in explicitly, e.g.: ``` symilar foo.py, bar.py, subpackage/spam.py, subpackage/eggs.py ``` **symilar** produces output like the following: ``` 17 similar lines in 2 files ==tests/data/clientmodule_test.py:3 ==tests/data/suppliermodule_test.py:12 class Ancestor: """ Ancestor method """ cls_member = DoNothing() def __init__(self, value): local_variable = 0 self.attr = 'this method shouldn\'t have a docstring' self.__value = value def get_value(self): """ nice docstring ;-) """ return self.__value def set_value(self, value): self.__value = value return 'this method shouldn\'t have a docstring' TOTAL lines=58 duplicates=17 percent=29.31 ``` ### 4.x This is the full list of change in pylint 4.x minors, by categories. ### What's New in Pylint 4.0 :Release:4.0 :Date: 2025-10-12 ### Summary -- Release highlights - • Pylint now supports Python 3.14. - • Pylint's inference engine (**astroid**) is now much more precise, understanding implicit booleanness and ternary expressions. (Thanks @zenlyj!) Consider this example: ``` class Result: errors: dict | None = None result = Result() if result.errors: result.errors[field_key] # inference engine understands result.errors cannot be None # pylint no longer raises unsubscriptable-object ``` The required **astroid** version is now 4.0.0. See the astroid changelog \ for additional fixes, features, and performance improvements applicable to pylint. - • Handling of **invalid-name** at the module level was patchy. Now, module-level constants that are reassigned are treated as variables and checked against **--variable-rgx** rather than **--const-rgx**. Module-level lists, sets, and objects can pass against either regex. Here, **LIMIT** is reassigned, so pylint only uses **--variable-rgx**: ``` LIMIT = 500 # [invalid-name] if sometimes: LIMIT = 1 # [invalid-name] ``` If this is undesired, refactor using *exclusive* assignment so that it is evident that this assignment happens only once: ``` if sometimes: LIMIT = 1 else: LIMIT = 500 # exclusive assignment: uses const regex, no warning ``` Lists, sets, and objects still pass against either **const-rgx** or **variable-rgx** even if reassigned, but are no longer completely skipped: ``` MY_LIST = [] my_list = [] My_List = [] # [invalid-name] ``` Remember to adjust the regexes \ and allow lists \ to your liking. ### What's new in Pylint 4.0.7? Release date: 2026-08-09 ### False Positives Fixed - • Fix a false positive for **invalid-name** when a module-level variable is assigned an instance of a **TypedDict** subclass. Such a name is a value, not a type definition, so it is now checked against the constant or variable regex instead of **class-rgx**. Closes #11231 (#11231 \) ### Other Bug Fixes - • Fix a crash in the **bad-open-mode** check when the **mode** argument of **open** is the **NotImplemented** constant (Python \>= 3.14). Closes #11099 (#11099 \) - • Fix a crash in the **not-context-manager** and **not-async-context-manager** checks when the context manager infers to a value without a name, such as the **slice** returned by **with slice(...)** / **async with slice(...)**. Closes #11102 (#11102 \) - • Fix a false positive for **nested-min-max** (**W3301**) when the inner **min**/**max** call carries a keyword argument such as **key=**. Flattening the call dropped the keyword and changed the result, so nested calls whose inner call has keyword arguments are no longer flagged. Closes #11130 (#11130 \) - • Fix a false suggestion from **nested-min-max** (**W3301**): when rewriting a nested **min**/**max** into a splat call, arguments positioned after the splatted call were silently dropped, so the suggested code changed the result. Closes #11134 (#11134 \) - • Fix a false positive for **too-many-locals** (**R0914**): PEP 695 type parameters, i.e. the **T1** and **T2** in a generic **def f\[T1, T2\]** signature, were counted as local variables. They are type-system constructs, not runtime locals, and are now excluded from the local-variable count. Closes #11136 (#11136 \) - • Fix *literal-comparison* (*R0123*) emitting a corrupted suggestion for identifiers that contain **is** (e.g. **axis is 5** was rendered **ax== == 5**). The suggestion is now rebuilt from the operands and operator. Closes #11146 (#11146 \) - • Fix false positives in *bad-string-format-type* (*E1307*) for valid **%** formatting: **%i**/**%u** applied to a float (both truncate like **%d**) and **%a** applied to any non-int type (**%a** is type-agnostic like **%s**/**%r**). Closes #11147 (#11147 \) - • Fix a false positive for useless-parent-delegation / W0246 \<#useless-parent-delegation\> when an override changes the default value of a positional-only parameter. Closes #11148 (#11148 \) - • Fixed a crash in **comparison-with-callable** when comparing a lambda assigned as a class attribute. Closes #11175 (#11175 \) - • **too-many-lines** could be reported at the line of a **# pylint: disable=too-many-lines** pragma found in a previously linted module. Pragma positions are now reset between modules, so the message is reported at line 1 (or at the current module's own pragma) regardless of which files were linted before. Refs #11191 (#11191 \) - • Fix a crash when a call unpacks a dictionary whose keys are not string constants, e.g. **copy.copy(\*\*{-1: 1})**. Closes #11222 (#11222 \) ### What's new in Pylint 4.0.6? Release date: 2026-06-14 ### False Positives Fixed - • **implicit-str-concat** is no longer emitted for an implicit concatenation of a raw string with a non-raw one (e.g. **r"\\d" "\\n"**). Such literals cannot be merged into a single string, so the concatenation is intentional rather than a forgotten comma. Closes #6663 (#6663 \) - • Fix a false positive for **invalid-name** (C0103) where the default **typevar-rgx** rejected **TypeVar** names containing digits, such as **Ec2T**. Closes #8499 (#8499 \) - • Fix a false positive for **too-many-arguments** in (non-static) methods and classmethods. Closes #8675 (#8675 \) - • Fix a false positive for **no-member** when a value is inferred to several possible types and at least one of them defines a dynamic **\_\_getattr\_\_**. Closes #9833 (#9833 \) - • Fix a false positive for **function-redefined** (E0102) when reusing names that match **dummy-variables-rgx** (such as **\_**), which is common for **pytest-bdd** step definitions. This restores the behavior from before pylint 4.0.0; as a consequence the false negative fixed in #9894 is reintroduced for functions whose name matches **dummy-variables-rgx**. Closes #10665 (#10665 \) - • Fix **undefined-variable** false positive when a name used as a **metaclass** argument in a nested class is referenced again later in the module. Closes #10823 (#10823 \) - • Fix a false positive for **unused-variable** where global variables matching **dummy-variables-rgx** were still reported as unused when **allow-global-unused-variables** was disabled. Closes #10890 (#10890 \) - • Fix a false positive for **bad-dunder-name** when there is a user-defined **\_\_suppress\_context\_\_** attribute on exception subclasses. Closes #10960 (#10960 \) - • Fix **used-before-assignment** false positive for names bound by **from X import \*** in every branch of an **if**/**elif**/**else** chain. Refs #10980 (#10980 \) - • Check for metaclass \_\_call\_\_ signature when evaluating arguments of a class call. Closes #11032 (#11032 \) - • Fix false positive **method-hidden** when **cached\_property** is imported directly with **from functools import cached\_property**. Refs #11037 (#11037 \) ### Other Bug Fixes - • Fix the suggestion of **unnecessary-comprehension** for a dict comprehension that iterates a dict directly, e.g. **{a: b for a, b in d}**. Iterating a dict yields its keys, so the suggestion is now **dict(d.keys())** instead of the incorrect **dict(d)**, which would simply copy **d**. Closes #8256 (#8256 \) - • Fix a crash in **consider-using-enumerate** when the **for** loop target is an attribute (e.g. **for self.idx in range(len(x))**) rather than a simple variable name. Closes #10099 (#10099 \) - • Fix crash when checking **attribute-defined-outside-init** on classes that inherit from a base class pylint cannot fully analyze. Closes #10892 (#10892 \) - • Fix **add\_message** silently overwriting an explicit **col\_offset=0** (or any other zero-valued **line**/**end\_lineno**/**end\_col\_offset**) with the AST node's value. The internal **\_add\_one\_message** helper used a falsey check (**if not col\_offset:**) to detect an omitted argument, which incorrectly treated a legitimate **0** the same as **None**. It now uses an identity check against **None**. Refs #11020 (#11020 \) - • Fix a crash in the name checker when a non-constant value is passed as the **covariant** or **contravariant** argument of a **TypeVar**. Closes #11022 (#11022 \) - • Fix a crash in the variable checker when a name resolves to a dataclass-synthesized **\_\_init\_\_**, which has no line number. Closes #11023 (#11023 \) - • Fix a crash in the variables checker when **NotImplemented** is used as the test of an **if** statement, which raised a **TypeError** in a boolean context on Python 3.14. Closes #11025 (#11025 \) - • Avoided a crash from the implicit booleaness checker for **len()** calls without arguments. Closes #11028 (#11028 \) - • Fix a crash in the variables checker when a class declares a metaclass whose attribute-access chain does not bottom out at a name (e.g. **class C(metaclass=None.\_)**). Originally reported as **pylint-dev/astroid#3066**. Refs #11031 (#11031 \) - • Fix a crash in the name checker when a chained assignment of a **TypeAlias** value has a non-name target such as a **Subscript** (for example **a\[0\] = b = TypeAlias**). Closes #11056 (#11056 \) - • Fix a crash in the deprecated checker when **\_\_import\_\_** is called with a non-string constant argument (for example **\_\_import\_\_(1)**). Closes #11059 (#11059 \) - • Avoid crashing when enum member inference fails while checking enum subclasses. Closes #11069 (#11069 \) - • Prevent a crash in **unexpected-keyword-arg** analysis when **infer\_call\_result()** raises **InferenceError** while inspecting decorator return signatures. Closes #11070 (#11070 \) - • Fix a crash in the typecheck checker when a class uses a non-class object (for example a function) as its **metaclass=** argument. Closes #11071 (#11071 \) - • Allow digits in ParamSpec and TypeVarTuple names for *invalid-name* check. The default *paramspec-rgx* and *typevartuple-rgx* patterns rejected names containing digits (e.g. **Ec2P**, **S3Ts**), emitting a false **invalid-name** (C0103). Allow digits in the lowercase segments, consistent with the **typevar** and **typealias** patterns. Closes #11090 (#11090 \) ### Performance Improvements - • The duplicate-code checker no longer runs when its message (R0801) is disabled, even if **reports=yes** is set. Previously, the checker's report (RP0801) would cause the expensive similarity computation to run regardless. Closes #3443 (#3443 \) ### What's new in Pylint 4.0.5? Release date: 2026-02-20 ### False Positives Fixed - • Fix possibly-used-before-assignment false positive when using self.fail() in tests. Closes #10743 (#10743 \) - • Fixed false positive for **logging-unsupported-format** when no arguments are provided to logging functions. According to Python's logging documentation, no formatting is performed when no arguments are supplied, so strings like **logging.error("%test")** are valid. Closes #10752 (#10752 \) - • Fix a false positive for **invalid-name** where a dataclass field typed with **Final** was evaluated against the **class\_const** regex instead of the **class\_attribute** regex. Closes #10790 (#10790 \) - • Avoid emitting *unspecified-encoding* (W1514) when *py-version* is 3.15+. Refs #10791 (#10791 \) ### Other Bug Fixes - • Fix *--known\_third\_party* config being ignored. Closes #10801 (#10801 \) - • Fixed dynamic color mapping for "fail-on" messages when using multiple reporter/output formats. Closes #10825 (#10825 \) - • dependency on isort is now set to \<9, permitting to use isort 8. Closes #10857 (#10857 \) ### What's new in Pylint 4.0.4? Release date: 2025-11-30 ### False Positives Fixed - • Fixed false positive for **invalid-name** where module-level constants were incorrectly classified as variables when a class-level attribute with the same name exists. Closes #10719 (#10719 \) - • Fix a false positive for **invalid-name** on an UPPER\_CASED name inside an **if** branch that assigns an object. Closes #10745 (#10745 \) ### What's new in Pylint 4.0.3? Release date: 2025-11-13 ### False Positives Fixed - • Add Enum dunder methods **\_generate\_next\_value\_**, **\_missing\_**, **\_numeric\_repr\_**, **\_add\_alias\_**, and **\_add\_value\_alias\_** to the list passed to **--good-dunder-names**. Closes #10435 (#10435 \) - • Fixed false positive for **invalid-name** with **typing.Annotated**. Closes #10696 (#10696 \) - • Fix false positive for **f-string-without-interpolation** with template strings when using format spec. Closes #10702 (#10702 \) - • Fix a false positive when an UPPER\_CASED class attribute was raising an **invalid-name** when typed with **Final**. Closes #10711 (#10711 \) - • Fix a false positive for **unbalanced-tuple-unpacking** when a tuple is assigned to a function call and the structure of the function's return value is ambiguous. Closes #10721 (#10721 \) ### Other Bug Fixes - • Make 'ignore' option work as expected again. Closes #10669 (#10669 \) - • Fix crash for **consider-using-assignment-expr** when a variable annotation without assignment is used as the **if** test expression. Closes #10707 (#10707 \) - • Fix crash for **prefer-typing-namedtuple** and **consider-math-not-float** when a **slice** object is called. Closes #10708 (#10708 \) ### What's new in Pylint 4.0.2? Release date: 2025-10-20 ### False Positives Fixed - • Fix false positive for invalid-name / C0103 \<#invalid-name\> on a partially uninferable module-level constant. Closes #10652 (#10652 \) - • Fix a false positive for invalid-name / C0103 \<#invalid-name\> on exclusive module-level assignments composed of three or more branches. We won't raise disallowed-name / C0104 \<#disallowed-name\> on module-level names that can't be inferred until a further refactor to remove this false negative is done. Closes #10664 (#10664 \) - • Fix false positive for invalid-name / C0103 \<#invalid-name\> for **TypedDict** instances. Closes #10672 (#10672 \) ### What's new in Pylint 4.0.1? Release date: 2025-10-14 ### False Positives Fixed - • Exclude **\_\_all\_\_** and **\_\_future\_\_.annotations** from **unused-variable**. Closes #10019 (#10019 \) - • Fix false-positive for **bare-name-capture-pattern** if a case guard is used. Closes #10647 (#10647 \) - • Check enums created with the **Enum()** functional syntax to pass against the **--class-rgx** for the invalid-name / C0103 \<#invalid-name\> check, like other enums. Closes #10660 (#10660 \) ### What's new in Pylint 4.0.0? Release date: 2025-10-12 ### Breaking Changes - • **invalid-name** now distinguishes module-level constants that are assigned only once from those that are reassigned and now applies **--variable-rgx** to the latter. Values other than literals (lists, sets, objects) can pass against either the constant or variable regexes (e.g. "LOGGER" or "logger" but not "LoGgEr"). Remember that **--good-names** or **--good-names-rgxs** can be provided to explicitly allow good names. Closes #3585 (#3585 \) - • The unused **pylintrc** argument to **PyLinter.\_\_init\_\_()** is deprecated and will be removed. Refs #6052 (#6052 \) - • Commented out code blocks such as **# bar() # TODO: remove dead code** will no longer emit **fixme**. Refs #9255 (#9255 \) - • **pyreverse** **Run** was changed to no longer call **sys.exit()** in its **\_\_init\_\_**. You should now call **Run(args).run()** which will return the exit code instead. Having a class that always raised a **SystemExit** exception was considered a bug. Normal usage of pyreverse through the CLI will not be affected by this change. Refs #9689 (#9689 \) - • The **suggestion-mode** option was removed, as pylint now always emits user-friendly hints instead of false-positive error messages. You should remove it from your conf if it's defined. Refs #9962 (#9962 \) - • The **async.py** checker module has been renamed to **async\_checker.py** since **async** is a Python keyword and cannot be imported directly. This allows for better testing and extensibility of the async checker functionality. Refs #10071 (#10071 \) - • The message-id of **continue-in-finally** was changed from **E0116** to **W0136**. The warning is now emitted for every Python version since it will raise a syntax warning in Python 3.14. See PEP 765 - Disallow return/break/continue that exit a finally block \. Refs #10480 (#10480 \) - • Removed support for **nmp.NaN** alias for **numpy.NaN** being recognized in 'nan-comparison / W0177 \<#nan-comparison\>'. Use **np** or **numpy** instead. Refs #10583 (#10583 \) - • Version requirement for **isort** has been bumped to \>=5.0.0. The internal compatibility for older **isort** versions exposed via **pylint.utils.IsortDriver** has been removed. Refs #10637 (#10637 \) ### New Features - • - **comparison-of-constants now uses the unicode from the ast instead of reformatting from** the node's values preventing some bad formatting due to **utf-8** limitation. The message now uses **"** instead of **'** to better work with what the python ast returns. Refs #8736 (#8736 \) - • Enhanced pyreverse to properly distinguish between UML relationship types (association, aggregation, composition) based on object ownership semantics. Type annotations without assignment are now treated as associations, parameter assignments as aggregations, and object instantiation as compositions. Closes #9045 Closes #9267 (#9045 \) - • The **fixme** check can now search through docstrings as well as comments, by using **check-fixme-in-docstring = true** in the **\[tool.pylint.miscellaneous\]** section. Closes #9255 (#9255 \) - • The **use-implicit-booleaness-not-x** checks now distinguish between comparisons used in boolean contexts and those that are not, enabling them to provide more accurate refactoring suggestions. Closes #9353 (#9353 \) - • The verbose option now outputs the filenames of the files that have been checked. Previously, it only included the number of checked and skipped files. Closes #9357 (#9357 \) - • colorized reporter now colorizes messages/categories that have been configured as **fail-on** in red inverse. This makes it easier to quickly find the errors that are causing pylint CI job failures. Closes #9898 (#9898 \) - • Enhanced support for @property decorator in pyreverse to correctly display return types of annotated properties when generating class diagrams. Closes #10057 (#10057 \) - • Add --max-depth option to pyreverse to control diagram complexity. A depth of 0 shows only top-level packages, 1 shows one level of subpackages, etc. This helps manage visualization of large codebases by limiting the depth of displayed packages and classes. Refs #10077 (#10077 \) - • Handle deferred evaluation of annotations in Python 3.14. Closes #10149 (#10149 \) - • Enhanced pyreverse to properly detect aggregations for comprehensions (list, dict, set, generator). Closes #10236 (#10236 \) - • **pyreverse**: add support for colorized output when using output format **mmd** (MermaidJS) and **html**. Closes #10242 (#10242 \) - • pypy 3.11 is now officially supported. Refs #10287 (#10287 \) - • Add support for Python 3.14. Refs #10467 (#10467 \) - • Add naming styles for **ParamSpec** and **TypeVarTuple** that align with the **TypeVar** style. Refs #10541 (#10541 \) ### New Checks - • Add **match-statements** checker and the following message: **bare-name-capture-pattern**. This will emit an error message when a name capture pattern is used in a match statement which would make the remaining patterns unreachable. This code is a SyntaxError at runtime. Closes #7128 (#7128 \) - • Add new check **async-context-manager-with-regular-with** to detect async context managers used with regular **with** statements instead of **async with**. Refs #10408 (#10408 \) - • Add **break-in-finally** warning. Using **break** inside the **finally** clause will raise a syntax warning in Python 3.14. See PEP 765 - Disallow return/break/continue that exit a finally block \. Refs #10480 (#10480 \) - • Add new checks for invalid uses of class patterns in **match** \. - • invalid-match-args-definition / E1902 \<#invalid-match-args-definition\> is emitted if **object.\_\_match\_args\_\_** \ isn't a tuple of strings. - • too-many-positional-sub-patterns / E1903 \<#too-many-positional-sub-patterns\> if there are more positional sub-patterns than specified in **object.\_\_match\_args\_\_** \. - • multiple-class-sub-patterns / E1904 \<#multiple-class-sub-patterns\> if there are multiple sub-patterns for the same attribute. Refs #10559 (#10559 \) - • Add additional checks for suboptimal uses of class patterns in **match** \. - • match-class-bind-self / R1905 \<#match-class-bind-self\> is emitted if a name is bound to **self** instead of using an **as** pattern. - • match-class-positional-attributes / R1906 \<#match-class-positional-attributes\> is emitted if a class pattern has positional attributes when keywords could be used. Refs #10587 (#10587 \) - • Add a **consider-math-not-float** message. **float("nan")** and **float("inf")** are slower than their counterpart **math.inf** and **math.nan** by a factor of 4 (notwithstanding the initial import of math) and they are also not well typed when using mypy. This check also catches typos in float calls as a side effect. The Code Style checker \<#pylint-extensions-code-style\> need to be activated for this check to work. Refs #10621 (#10621 \) ### False Positives Fixed - • Fix a false positive for **used-before-assignment** when a variable defined under an **if** and via a named expression (walrus operator) is used later when guarded under the same **if** test. Closes #10061 (#10061 \) - • Fix no-name-in-module / E0611 \<#no-name-in-module\> for members of **concurrent.futures** with Python 3.14. Closes #10632 (#10632 \) ### False Negatives Fixed - • Fix false negative for **used-before-assignment** when a **TYPE\_CHECKING** import is used as a type annotation prior to erroneous usage. Refs #8893 (#8893 \) - • Match cases are now counted as edges in the McCabe graph and will increase the complexity accordingly. Refs #9667 (#9667 \) - • Check module-level constants with type annotations for **invalid-name**. Remember to adjust **const-naming-style** or **const-rgx** to your liking. Closes #9770 (#9770 \) - • Fix false negative where function-redefined (E0102) was not reported for functions with a leading underscore. Closes #9894 (#9894 \) - • We now raise a **logging-too-few-args** for format string with no interpolation arguments at all (i.e. for something like **logging.debug("Awaiting process %s")** or **logging.debug("Awaiting process {pid}")**). Previously we did not raise for such case. Closes #9999 (#9999 \) - • Fix false negative for **used-before-assignment** when a function is defined inside a **TYPE\_CHECKING** guard block and used later. Closes #10028 (#10028 \) - • Fix a false negative for **possibly-used-before-assignment** when a variable is conditionally defined and later assigned to a type-annotated variable. Closes #10421 (#10421 \) - • Fix false negative for **deprecated-module** when a **\_\_import\_\_** method is used instead of **import** sentence. Refs #10453 (#10453 \) - • Count match cases for **too-many-branches** check. Refs #10542 (#10542 \) - • Fix false-negative where unused-import / W0611 \<#unused-import\> was not reported for names referenced in a preceding **global** statement. Refs #10633 (#10633 \) ### Other Bug Fixes - • When displaying unicode with surrogates (or other potential **UnicodeEncodeError**), pylint will now display a '?' character (using **encode(encoding="utf-8", errors="replace")**) instead of crashing. The functional tests classes are also updated to handle this case. Closes #8736. (#8736 \) - • Fixed unidiomatic-typecheck only checking left-hand side. Closes #10217 (#10217 \) - • Fix a crash caused by malformed format strings when using **.format** with keyword arguments. Closes #10282 (#10282 \) - • Fix false positive **inconsistent-return-statements** when using **quit()** or **exit()** functions. Closes #10508 (#10508 \) - • Fix a crash in nested-min-max / W3301 \<#nested-min-max\> when using **builtins.min** or **builtins.max** instead of **min** or **max** directly. Closes #10626 (#10626 \) - • Fixed a crash in unnecessary-dict-index-lookup / R1733 \<#unnecessary-dict-index-lookup\> when the index of an enumerated list was deleted inside a for loop. Closes #10627 (#10627 \) ### Other Changes - • Remove support for launching pylint with Python 3.9. Code that supports Python 3.9 can still be linted with the **--py-version=3.9** setting. Refs #10405 (#10405 \) ### Internal Changes - • Modified test framework to allow for different test output for different Python versions. Refs #10382 (#10382 \) ### 3.x This is the full list of change in pylint 3.x minors, by categories. ### What's New in Pylint 3.3 :Release:3.3 :Date: 2024-09-20 ### Summary -- Release highlights ### What's new in Pylint 3.3.9? Release date: 2025-10-05 ### False Positives Fixed - • Fix used-before-assignment / E0601 \<#used-before-assignment\> for PEP 695 type aliases and parameters. Closes #9815 (#9815 \) - • No longer flag undeprecated functions in **importlib.resources** as deprecated. Closes #10593 (#10593 \) - • Fix false positive **inconsistent-return-statements** when using **quit()** or **exit()** functions. Closes #10508 (#10508 \) - • Fix false positive **undefined-variable** (E0602) for for-loop variable shadowing patterns like **for item in item:** when the variable was previously defined. Closes #10562 (#10562 \) ### Other Bug Fixes - • Fixed crash in **unnecessary-list-index-lookup** when starting an enumeration using minus the length of an iterable inside a dict comprehension when the len call was only made in this dict comprehension, and not elsewhere. Also changed the approach, to use inference in all cases but the simple ones, so we don't have to fix crashes one by one for arbitrarily complex expressions in enumerate. Closes #10510 (#10510 \) ### What's new in Pylint 3.3.8? Release date: 2025-08-09 This patch release includes an exceptional fix for a false negative issue. For details, see: \ ### False Positives Fixed - • Fix false positives for possibly-used-before-assignment / E0606 \<#possibly-used-before-assignment\> when variables are exhaustively assigned within a **match** \ block. Closes #9668 (#9668 \) - • Fix false positive for missing-raises-doc / W9006 \<#missing-raises-doc\> and missing-yield-doc / W9013 \<#missing-yield-doc\> when the method length is less than docstring-min-length. Refs #10104 (#10104 \) - • Fix a false positive for unused-variable / W0612 \<#unused-variable\> when multiple except handlers bind the same name under a try block. Closes #10426 (#10426 \) ### False Negatives Fixed - • Fix false-negative for used-before-assignment / E0601 \<#used-before-assignment\> with **from \_\_future\_\_ import annotations** in function definitions. Refs #10482 (#10482 \) ### Other Bug Fixes - • Fix a bug in Pyreverse where aggregations and associations were included in diagrams regardless of the selected --filter-mode (such as PUB\_ONLY, ALL, etc.). Closes #10373 (#10373 \) - • Fix double underscores erroneously rendering as bold in pyreverse's Mermaid output. Closes #10402 (#10402 \) ### What's new in Pylint 3.3.7? Release date: 2025-05-04 ### False Positives Fixed - • Comparisons between two calls to *type()* won't raise an unidiomatic-typecheck / C0123 \<#unidiomatic-typecheck\> warning anymore, consistent with the behavior applied only for **==** previously. Closes #10161 (#10161 \) ### Other Bug Fixes - • Fixed a crash when importing a class decorator that did not exist with the same name as a class attribute after the class definition. Closes #10105 (#10105 \) - • Fix a crash caused by malformed format strings when using *.format* with keyword arguments. Closes #10282 (#10282 \) - • Using a slice as a class decorator now raises a not-callable / E1102 \<#not-callable\> message instead of crashing. A lot of checks that dealt with decorators (too many to list) are now shortcut if the decorator can't immediately be inferred to a function or class definition. Closes #10334 (#10334 \) ### Other Changes - • The algorithm used for no-member / E1101 \<#no-member\> suggestions is now more efficient and cuts the calculation when the distance score is already above the threshold. Refs #10277 (#10277 \) ### What's new in Pylint 3.3.6? Release date: 2025-03-20 ### False Positives Fixed - • Fix a false positive for used-before-assignment / E0601 \<#used-before-assignment\> when an inner function's return type annotation is a class defined at module scope. Closes #9391 (#9391 \) ### What's new in Pylint 3.3.5? Release date: 2025-03-09 ### False Positives Fixed - • Fix false positives for use-implicit-booleaness-not-comparison / C1803 \<#use-implicit-booleaness-not-comparison\>, use-implicit-booleaness-not-comparison-to-string / C1804 \<#use-implicit-booleaness-not-comparison-to-string\> and use-implicit-booleaness-not-comparison-to-zero / C1805 \<#use-implicit-booleaness-not-comparison-to-zero\> when chained comparisons are checked. Closes #10065 (#10065 \) - • Fix a false positive for invalid-getnewargs-ex-returned / E0313 \<#invalid-getnewargs-ex-returned\> when the tuple or dict has been assigned to a name. Closes #10208 (#10208 \) - • Remove **getopt** \ and **optparse** \ from the list of deprecated modules. Closes #10211 (#10211 \) ### Other Bug Fixes - • Fixed conditional import x.y causing false positive possibly-used-before-assignment / E0606 \<#possibly-used-before-assignment\>. Closes #10081 (#10081 \) - • Fix a crash when something besides a class is found in an except handler. Closes #10106 (#10106 \) - • Fixed raising invalid-name / C0103 \<#invalid-name\> when using camelCase for private methods with two leading underscores. Closes #10189 (#10189 \) ### Other Changes - • Upload release assets to PyPI via Trusted Publishing. Closes #10256 (#10256 \) ### What's new in Pylint 3.3.4? Release date: 2025-01-28 ### Other Bug Fixes - • Fixes "skipped files" count calculation; the previous method was displaying an arbitrary number. Closes #10073 (#10073 \) - • Fixes a crash that occurred when pylint was run in a container on a host with cgroupsv2 and restrictions on CPU usage. Closes #10103 (#10103 \) - • Relaxed the requirements for isort so pylint can benefit from isort 6. Closes #10203 (#10203 \) ### What's new in Pylint 3.3.3? Release date: 2024-12-23 ### False Positives Fixed - • Fix false positives for undefined-variable / E0602 \<#undefined-variable\> for classes using Python 3.12 generic type syntax. Closes #9335 (#9335 \) - • Fix a false positive for use-implicit-booleaness-not-len / C1802 \<#use-implicit-booleaness-not-len\>. No lint should be emitted for generators (**len()** \ is not defined for generators). Refs #10100 (#10100 \) ### Other Bug Fixes - • Fix **Unable to import 'collections.abc' (import-error)** on Python 3.13.1. Closes #10112 (#10112 \) ### What's new in Pylint 3.3.2? Release date: 2024-12-01 ### False Positives Fixed - • Fix a false positive for potential-index-error / E0643 \<#potential-index-error\> when an indexed iterable contains a starred element that evaluates to more than one item. Closes #10076 (#10076 \) ### Other Bug Fixes - • Fixes the issue with --source-root option not working when the source files are in a subdirectory of the source root (e.g. when using a /src layout). Closes #10026 (#10026 \) ### What's new in Pylint 3.3.1? Release date: 2024-09-24 ### False Positives Fixed - • Fix regression causing some f-strings to not be inferred as strings. Closes #9947 (#9947 \) ### What's new in Pylint 3.3.0? Release date: 2024-09-20 ### Changes requiring user actions - • We migrated **symilar** to argparse, from getopt, so the error and help output changed (for the better). We exit with 2 instead of sometime 1, sometime 2. The error output is not captured by the runner anymore. It's not possible to use a value for the boolean options anymore (**--ignore-comments 1** should become **--ignore-comments**). Refs #9731 (#9731 \) ### New Features - • Add new declare-non-slot / E0245 \<#declare-non-slot\> error which reports when a class has a *\_\_slots\_\_* member and a type hint on the class is not present in *\_\_slots\_\_*. Refs #9499 (#9499 \) ### New Checks - • Added too-many-positional-arguments / R0917 \<#too-many-positional-arguments\> to allow distinguishing the configuration for too many total arguments (with keyword-only params specified after *\**) from the configuration for too many positional-or-keyword or positional-only arguments. As part of evaluating whether this check makes sense for your project, ensure you adjust the value of *--max-positional-arguments*. Closes #9099 (#9099 \) - • Add using-exception-groups-in-unsupported-version / W2603 \<#using-exception-groups-in-unsupported-version\> and using-generic-type-syntax-in-unsupported-version / W2604 \<#using-generic-type-syntax-in-unsupported-version\> for uses of Python 3.11+ or 3.12+ features on lower supported versions provided with **--py-version**. Closes #9791 (#9791 \) - • Add using-assignment-expression-in-unsupported-version / W2605 \<#using-assignment-expression-in-unsupported-version\> for uses of **:=** (walrus operator) on Python versions below 3.8 provided with **--py-version**. Closes #9820 (#9820 \) - • Add using-positional-only-args-in-unsupported-version / W2606 \<#using-positional-only-args-in-unsupported-version\> for uses of positional-only args on Python versions below 3.8 provided with **--py-version**. Closes #9823 (#9823 \) - • Add unnecessary-default-type-args / R6007 \<#unnecessary-default-type-args\> to the **typing** extension to detect the use of unnecessary default type args for **typing.Generator** \ and **typing.AsyncGenerator** \. Refs #9938 (#9938 \) ### False Negatives Fixed - • Fix computation of never-returning function: **typing.Never** \ is handled in addition to **typing.NoReturn** \, and priority is given to the explicit *--never-returning-functions* option. Closes #7565. (#7565 \) - • Fix a false negative for await-outside-async / E1142 \<#await-outside-async\> when await is inside Lambda. Refs #9653 (#9653 \) - • Fix a false negative for duplicate-argument-name / E0108 \<#duplicate-argument-name\> by including **positional-only**, **\*args** and **\*\*kwargs** arguments in the check. Closes #9669 (#9669 \) - • Fix false negative for multiple-statements / C0321 \<#multiple-statements\> when multiple statements are present on **else** \ and **finally** \ lines of **try** \. Refs #9759 (#9759 \) - • Fix false negatives when :py:func::*isinstance* does not have exactly two arguments. pylint now emits a too-many-function-args / E1121 \<#too-many-function-args\> or no-value-for-parameter / E1120 \<#no-value-for-parameter\> appropriately for **isinstance()** \ calls. Closes #9847 (#9847 \) ### Other Bug Fixes - • *--enable* with *--disable=all* now produces an error, when an unknown msg code is used. Internal *pylint* messages are no longer affected by *--disable=all*. Closes #9403 (#9403 \) - • Impossible to compile regexes for paths in the configuration or argument given to pylint won't crash anymore but raise an argparse error and display the error message from **re.compile** instead. Closes #9680 (#9680 \) - • Fix a bug where a **tox.ini** file with pylint configuration was ignored and it exists in the current directory. **.cfg** and **.ini** files containing a **Pylint** configuration may now use a section named **\[pylint\]**. This enhancement impacts the scenario where these file types are used as defaults when they are present and have not been explicitly referred to, using the **--rcfile** option. Closes #9727 (#9727 \) - • Improve file discovery for directories that are not python packages. Closes #9764 (#9764 \) ### Other Changes - • Remove support for launching pylint with Python 3.8. Code that supports Python 3.8 can still be linted with the **--py-version=3.8** setting. Refs #9774 (#9774 \) - • Add support for Python 3.13. Refs #9852 (#9852 \) ### Internal Changes - • All variables, classes, functions and file names containing the word 'similar', when it was, in fact, referring to 'symilar' (the standalone program for the duplicate-code / R0801 \<#duplicate-code\> check) were renamed to 'symilar'. Closes #9734 (#9734 \) - • Remove old-style classes (Python 2) code and remove check for new-style class since everything is new-style in Python 3. Updated doc for exception checker to remove reference to new style class. Refs #9925 (#9925 \) ### What's New in Pylint 3.2 - **Release** 3\.2 - **Date** TBA ### Summary -- Release highlights ### What's new in Pylint 3.2.7? Release date: 2024-08-31 ### False Positives Fixed - • Fixed a false positive *unreachable* for *NoReturn* coroutine functions. Closes #9840. (#9840 \) ### Other Bug Fixes - • Fix crash in refactoring checker when calling a lambda bound as a method. Closes #9865 (#9865 \) - • Fix a crash in **undefined-loop-variable** when providing the **iterable** argument to **enumerate()**. Closes #9875 (#9875 \) - • Fix to address indeterminacy of error message in case a module name is same as another in a separate namespace. Refs #9883 (#9883 \) ### What's new in Pylint 3.2.6? Release date: 2024-07-21 ### False Positives Fixed - • Quiet false positives for *unexpected-keyword-arg* when pylint cannot determine which of two or more dynamically defined classes is being instantiated. Closes #9672 (#9672 \) - • Fix a false positive for **missing-param-doc** where a method which is decorated with **typing.overload** was expected to have a docstring specifying its parameters. Closes #9739 (#9739 \) - • Fix a regression that raised **invalid-name** on class attributes merely overriding invalid names from an ancestor. Closes #9765 (#9765 \) - • Treat *assert\_never()* the same way when imported from *typing\_extensions*. Closes #9780 (#9780 \) - • Fix a false positive for *consider-using-min-max-builtin* when the assignment target is an attribute. Refs #9800 (#9800 \) ### Other Bug Fixes - • Fix an *AssertionError* arising from properties that return partial functions. Closes #9214 (#9214 \) - • Fix a crash when a subclass extends **\_\_slots\_\_**. Closes #9814 (#9814 \) ### What's new in Pylint 3.2.5? Release date: 2024-06-28 ### Other Bug Fixes - • Fixed a false positive **unreachable-code** when using **typing.Any** as return type in python 3.8, the **typing.NoReturn** are not taken into account anymore for python 3.8 however. Closes #9751 (#9751 \) ### What's new in Pylint 3.2.4? Release date: 2024-06-26 ### False Positives Fixed - • Prevent emitting **possibly-used-before-assignment** when relying on names only potentially not defined in conditional blocks guarded by functions annotated with **typing.Never** or **typing.NoReturn**. Closes #9674 (#9674 \) ### Other Bug Fixes - • Fixed a crash when the lineno of a variable used as an annotation wasn't available for **undefined-variable**. Closes #8866 (#8866 \) - • Fixed a crash when the **start** value in an **enumerate** was non-constant and impossible to infer (like in\`\`enumerate(apples, start=int(random\_apple\_index)\`\`) for **unnecessary-list-index-lookup**. Closes #9078 (#9078 \) - • Fixed a crash in **symilar** when the **-d** or **-i** short option were not properly recognized. It's still impossible to do **-d=1** (you must do **-d 1**). Closes #9343 (#9343 \) ### What's new in Pylint 3.2.3? Release date: 2024-06-06 ### False Positives Fixed - • Classes with only an Ellipsis (**...**) in their body do not trigger multiple-statements / C0321 \<#multiple-statements\>' anymore if they are inlined (in accordance with black's 2024 style). Closes #9398 (#9398 \) - • Fix a false positive for **redefined-outer-name** when there is a name defined in an exception-handling block which shares the same name as a local variable that has been defined in a function body. Closes #9671 (#9671 \) - • Fix a false positive for **use-yield-from** when using the return value from the **yield** atom. Closes #9696 (#9696 \) ### What's new in Pylint 3.2.2? Release date: 2024-05-20 ### False Positives Fixed - • Fix multiple false positives for generic class syntax added in Python 3.12 (PEP 695). Closes #9406 (#9406 \) - • Exclude context manager without cleanup from **contextmanager-generator-missing-cleanup** checks. Closes #9625 (#9625 \) ### What's new in Pylint 3.2.1? Release date: 2024-05-18 ### False Positives Fixed - • Exclude if/else branches containing terminating functions (e.g. *sys.exit()*) from *possibly-used-before-assignment* checks. Closes #9627 (#9627 \) - • Don't emit **typevar-name-incorrect-variance** warnings for PEP 695 style TypeVars. The variance is inferred automatically by the type checker. Adding **\_co** or **\_contra** suffix can help to reason about TypeVar. Refs #9638 (#9638 \) - • Fix a false positive for *possibly-used-before-assignment* when using *typing.assert\_never()* (3.11+) to indicate exhaustiveness. Closes #9643 (#9643 \) ### Other Bug Fixes - • Fix a false negative for **--ignore-patterns** when the directory to be linted is specified using a dot(**.**) and all files are ignored instead of only the files whose name begin with a dot. Closes #9273 (#9273 \) - • Restore "errors / warnings by module" section to report output (with *-ry*). Closes #9145 (#9145 \) - • **trailing-comma-tuple** should now be correctly emitted when it was disabled globally but enabled via local message control, after removal of an over-optimisation. Refs #9608. (#9608 \) - • Add *--prefer-stubs=yes* option to opt-in to the astroid 3.2 feature that prefers *.pyi* stubs over same-named *.py* files. This has the potential to reduce *no-member* errors but at the cost of more errors such as *not-an-iterable* from function bodies appearing as *...*. Defaults to *no*. Closes #9626 Closes #9623 (#9626 \) ### Internal Changes - • Update astroid version to 3.2.1. This solves some reports of **RecursionError** and also makes the *prefer .pyi stubs* feature in astroid 3.2.0 *opt-in* with the aforementioned **--prefer-stubs=y** option. Refs #9139 (#9139 \) ### What's new in Pylint 3.2.0? Release date: 2024-05-14 ### New Features - • Understand *six.PY2* and *six.PY3* for conditional imports. Closes #3501 (#3501 \) - • A new *github* reporter has been added. This reporter returns the output of *pylint* in a format that Github can use to automatically annotate code. Use it with *pylint --output-format=github* on your Github Workflows. Closes #9443. (#9443 \) ### New Checks - • Add check **possibly-used-before-assignment** when relying on names after an **if/else** switch when one branch failed to define the name, raise, or return. Closes #1727 (#1727 \) - • Checks for generators that use contextmanagers that don't handle cleanup properly. Is meant to raise visibility on the case that a generator is not fully exhausted and the contextmanager is not cleaned up properly. A contextmanager must yield a non-constant value and not handle cleanup for GeneratorExit. The using generator must attempt to use the yielded context value *with x() as y* and not just *with x()*. Closes #2832 (#2832 \) ### False Negatives Fixed - • If and Try nodes are now checked for useless return statements as well. Closes #9449. (#9449 \) - • Fix false negative for **property-with-parameters** in the case of parameters which are **positional-only**, **keyword-only**, **variadic positional** or **variadic keyword**. Closes #9584 (#9584 \) ### False Positives Fixed pylint now understands the **@overload** decorator return values better. Closes #4696 (#4696 \) Refs #9606 (#9606 \) ### Performance Improvements - • Ignored modules are now not checked at all, instead of being checked and then ignored. This should speed up the analysis of large codebases which have ignored modules. Closes #9442 (#9442 \) (#9442 \) - • ImportChecker's logic has been modified to avoid context files when possible. This makes it possible to cache module searches on astroid and reduce execution times. Refs #9310. (#9310 \) - • An internal check for **trailing-comma-tuple** being enabled for a file or not is now done once per file instead of once for each token. Refs #9608. (#9608 \) ### What's New in Pylint 3.1 - **Release** 3\.1 - **Date** 2024-02-25 ### Summary -- Release highlights Two new checks -- **use-yield-from**, **deprecated-attribute** -- and a smattering of bug fixes. ### What's new in Pylint 3.1.1? Release date: 2024-05-13 ### False Positives Fixed - • Treat *attrs.define* and *attrs.frozen* as dataclass decorators in *too-few-public-methods* check. Closes #9345 (#9345 \) - • Fix a false positive with **singledispatchmethod-function** when a method is decorated with both **functools.singledispatchmethod** and **staticmethod**. Closes #9531 (#9531 \) - • Fix a false positive for **consider-using-dict-items** when iterating using **keys()** and then deleting an item using the key as a lookup. Closes #9554 (#9554 \) ### What's new in Pylint 3.1.0? Release date: 2024-02-25 ### New Features - • Skip **consider-using-join** check for non-empty separators if an **suggest-join-with-non-empty-separator** option is set to **no**. Closes #8701 (#8701 \) - • Discover **.pyi** files when linting. These can be ignored with the **ignore-patterns** setting. Closes #9097 (#9097 \) - • Check **TypeAlias** and **TypeVar** (PEP 695) nodes for **invalid-name**. Refs #9196 (#9196 \) - • Support for resolving external toml files named pylintrc.toml and .pylintrc.toml. Closes #9228 (#9228 \) - • Check for *.clear*, *.discard*, *.pop* and *remove* methods being called on a set while it is being iterated over. Closes #9334 (#9334 \) ### New Checks - • New message *use-yield-from* added to the refactoring checker. This message is emitted when yielding from a loop can be replaced by *yield from*. Closes #9229. (#9229 \) - • Added a **deprecated-attribute** message to check deprecated attributes in the stdlib. Closes #8855 (#8855 \) ### False Positives Fixed - • Fixed false positive for **inherit-non-class** for generic Protocols. Closes #9106 (#9106 \) - • Exempt **TypedDict** from **typing\_extensions** from **too-many-ancestor** checks. Refs #9167 (#9167 \) ### False Negatives Fixed - • Extend broad-exception-raised / W0719 \<#broad-exception-raised\> and broad-exception-caught / W0718 \<#broad-exception-caught\> to except\*. Closes #8827 (#8827 \) - • Fix a false-negative for unnecessary if blocks using a different than expected ordering of arguments. Closes #8947. (#8947 \) ### Other Bug Fixes - • Improve the message provided for wrong-import-order / C0411 \<#wrong-import-order\> check. Instead of the import statement ("import x"), the message now specifies the import that is out of order and which imports should come after it. As reported in the issue, this is particularly helpful if there are multiple imports on a single line that do not follow the PEP8 convention. The message will report imports as follows: For "import X", it will report "(standard/third party/first party/local) import X" For "import X.Y" and "from X import Y", it will report "(standard/third party/first party/local) import X.Y" The import category is specified to provide explanation as to why pylint has issued the message and guidance to the developer on how to fix the problem. Closes #8808 (#8808 \) ### Other Changes - • Print how many files were checked in verbose mode. Closes #8935 (#8935 \) - • Fix a crash when an enum class which is also decorated with a **dataclasses.dataclass** decorator is defined. Closes #9100 (#9100 \) ### Internal Changes - • Update astroid version to 3.1.0. Refs #9457 (#9457 \) ### What's New in Pylint 3.0 - **Release** 3\.0.0 - **Date** 2023-10-02 ### Summary -- Release highlights Pylint now support python 3.12 officially. This long anticipated major version also provides some important usability and performance improvements, along with enacting necessary breaking changes and long-announced deprecations. The documentation of each message with an example is very close too. The required **astroid** version is now 3.0.0. See the astroid changelog \ for additional fixes, features, and performance improvements applicable to pylint. Our code is now fully typed. The **invalid-name** message no longer checks for a minimum length of 3 characters by default. Dependencies like wrapt or setuptools were removed. A new **json2** reporter has been added. It features an enriched output that is easier to parse and provides more info, here's a sample output. ``` { "messages": [ { "type": "convention", "symbol": "line-too-long", "message": "Line too long (1/2)", "messageId": "C0301", "confidence": "HIGH", "module": "0123", "obj": "", "line": 1, "column": 0, "endLine": 1, "endColumn": 4, "path": "0123", "absolutePath": "0123" } ], "statistics": { "messageTypeCount": { "fatal": 0, "error": 0, "warning": 0, "refactor": 0, "convention": 1, "info": 0 }, "modulesLinted": 1, "score": 5.0 } } ``` ### What's new in Pylint 3.0.4? Release date: 2024-02-23 ### False Positives Fixed - • **used-before-assignment** is no longer emitted when using a name in a loop and depending on an earlier name assignment in an **except** block paired with **else: continue**. Closes #6804 (#6804 \) - • Avoid false positives for **no-member** involving function attributes supplied by decorators. Closes #9246 (#9246 \) - • Fixed false positive nested-min-max / W3301 \<#nested-min-max\> for nested lists. Closes #9307 (#9307 \) - • Fix false positive for **used-before-assignment** in a **finally** block when assignments took place in both the **try** block and each exception handler. Closes #9451 (#9451 \) ### Other Bug Fixes - • Catch incorrect ValueError **"generator already executing"** for Python 3.12.0 - 3.12.2. This is fixed upstream in Python 3.12.3. Closes #9138 (#9138 \) ### What's new in Pylint 3.0.3? Release date: 2023-12-11 ### False Positives Fixed - • Fixed false positive for **unnecessary-lambda** when the call has keyword arguments but not the lambda. Closes #9148 (#9148 \) - • Fixed incorrect suggestion for shallow copy in unnecessary-comprehension / R1721 \<#unnecessary-comprehension\> Example of the suggestion: #pylint: disable=:ref:*missing-module-docstring* a = \[1, 2, 3\] b = \[x for x in a\] b\[0\] = 0 print(a) # \[1, 2, 3\] After changing b = \[x for x in a\] to b = a based on the suggestion, the script now prints \[0, 2, 3\]. The correct suggestion should be use list(a) to preserve the original behavior. Closes #9172 (#9172 \) - • Fix false positives for **undefined-variable** and **unused-argument** for classes and functions using Python 3.12 generic type syntax. Closes #9193 (#9193 \) - • Fixed **pointless-string-statement** false positive for docstrings on Python 3.12 type aliases. Closes #9268 (#9268 \) - • Fix false positive for **invalid-exception-operation** when concatenating tuples of exception types. Closes #9288 (#9288 \) ### Other Bug Fixes - • Fix a bug where pylint was unable to walk recursively through a directory if the directory has an *\_\_init\_\_.py* file. Closes #9210 (#9210 \) ### What's new in Pylint 3.0.2? Release date: 2023-10-22 ### False Positives Fixed - • Fix **used-before-assignment** false positive for generic type syntax (PEP 695, Python 3.12). Closes #9110 (#9110 \) ### Other Bug Fixes - • Escape special symbols and newlines in messages. Closes #7874 (#7874 \) - • Fixes suggestion for **nested-min-max** for expressions with additive operators, list and dict comprehensions. Closes #8524 (#8524 \) - • Fixes ignoring conditional imports with **ignore-imports=y**. Closes #8914 (#8914 \) - • Emit **inconsistent-quotes** for f-strings with 3.12 interpreter only if targeting pre-3.12 versions. Closes #9113 (#9113 \) ### What's new in Pylint 3.0.1? Release date: 2023-10-05 ### False Positives Fixed - • Fixed false positive for **inherit-non-class** for generic Protocols. Closes #9106 (#9106 \) ### Other Changes - • Fix a crash when an enum class which is also decorated with a **dataclasses.dataclass** decorator is defined. Closes #9100 (#9100 \) ### What's new in Pylint 3.0.0? Release date: 2023-10-02 ### Breaking Changes - • Enabling or disabling individual messages will now take effect even if an **--enable=all** or **disable=all** follows in the same configuration file (or on the command line). This means for the following example, **fixme** messages will now be emitted: ``` pylint my_module --enable=fixme --disable=all ``` To regain the prior behavior, remove the superfluous earlier option. Closes #3696 (#3696 \) - • Remove support for launching pylint with Python 3.7. Code that supports Python 3.7 can still be linted with the **--py-version=3.7** setting. Refs #6306 (#6306 \) - • Disables placed in a **try** block now apply to the **except** block. Previously, they only happened to do so in the presence of an **else** clause. Refs #7767 (#7767 \) - • *pyreverse* now uses a new default color palette that is more colorblind friendly. The color scheme is taken from Paul Tol's Notes \. If you prefer other colors, you can use the *--color-palette* option to specify custom colors. Closes #8251 (#8251 \) - • Everything related to the **\_\_implements\_\_** construct was removed. It was based on PEP245 that was proposed in 2001 and rejected in 2006. The capability from pyreverse to take **\_\_implements\_\_** into account when generating diagrams was also removed. Refs #8404 (#8404 \) - • **pyreverse**: Support for the **.vcg** output format (Visualization of Compiler Graphs) has been dropped. Closes #8416 (#8416 \) - • The warning when the now useless old pylint cache directory (pylint.d) was found was removed. The cache dir is documented in the FAQ \. Refs #8462 (#8462 \) - • Following a deprecation period, **pylint.config.PYLINTRC** was removed. Use the **pylint.config.find\_default\_config\_files** generator instead. Closes #8862 (#8862 \) ### Changes requiring user actions - • The **invalid-name** message no longer checks for a minimum length of 3 characters by default. (This was an unadvertised commingling of concerns between casing and name length, and users regularly reported this to be surprising.) If checking for a minimum length is still desired, it can be regained in two ways: - • If you are content with a **disallowed-name** message (instead of **invalid-name**), then simply add the option **bad-names-rgxs="^..?$"**, which will fail 1-2 character-long names. (Ensure you enable **disallowed-name**.) - • If you would prefer an **invalid-name** message to be emitted, or would prefer finer-grained control over the circumstances in which messages are emitted (classes vs. methods, etc.), then avail yourself of the regex options described here \. (In particular, take note of the commented out options in the "example configuration" given at the bottom of the section.) The prior regexes can be found in the pull request \ that removed the length requirements. Closes #2018 (#2018 \) - • The compare to empty string checker (**pylint.extensions.emptystring**) and the compare to zero checker (**pylint.extensions.compare-to-zero**) have been removed and their checks are now part of the implicit booleaness checker: - • **compare-to-zero** was renamed **use-implicit-booleaness-not-comparison-to-zero** and **compare-to-empty-string** was renamed **use-implicit-booleaness-not-comparison-to-string** and they now need to be enabled explicitly. - • The **pylint.extensions.emptystring** and **pylint.extensions.compare-to-zero** extensions no longer exist and need to be removed from the **load-plugins** option. - • Messages related to implicit booleaness were made more explicit and actionable. This permits to make their likeness explicit and will provide better performance as they share most of their conditions to be raised. Closes #6871 (#6871 \) - • epylint was removed. It now lives at: \. Refs #7737 (#7737 \) - • The **overgeneral-exceptions** option now only takes fully qualified names into account (**builtins.Exception** not **Exception**). If you overrode this option, you need to use the fully qualified name now. There's still a warning, but it will be removed in 3.1.0. Refs #8411 (#8411 \) - • Following a deprecation period, it's no longer possible to use **MASTER** or **master** as configuration section in **setup.cfg** or **tox.ini**. It's bad practice to not start a section title with the tool name. Please use **pylint.main** instead. Refs #8465 (#8465 \) - • Package stats are now printed when running Pyreverse and a **--verbose** flag was added to get the original output with parsed modules. You might need to activate the verbose option if you want to keep the old output. Closes #8973 (#8973 \) ### New Features - • A new **json2** reporter has been added. It features a more enriched output that is easier to parse and provides more info. Compared to **json** the only changes are that messages are now under the **"messages"** key and that **"message-id"** now follows the camelCase convention and is renamed to **"messageId"**. The new reporter also reports the "score" of the modules you linted as defined by the **evaluation** option and provides statistics about the modules you linted. We encourage users to use the new reporter as the **json** reporter will no longer be maintained. Closes #4741 (#4741 \) - • In Pyreverse package dependency diagrams, show when a module imports another only for type-checking. Closes #8112 (#8112 \) - • Add new option (**--show-stdlib**, **-L**) to **pyreverse**. This is similar to the behavior of **--show-builtin** in that standard library modules are now not included by default, and this option will include them. Closes #8181 (#8181 \) - • Add Pyreverse option to exclude standalone nodes from diagrams with *--no-standalone*. Closes #8476 (#8476 \) ### New Checks - • Added **DataclassChecker** module and **invalid-field-call** checker to check for invalid dataclasses.field() usage. Refs #5159 (#5159 \) - • Add **return-in-finally** to emit a message if a return statement was found in a finally clause. Closes #8260 (#8260 \) - • Add a new message **kwarg-superseded-by-positional-arg** to warn when a function is called with a keyword argument which shares a name with a positional-only parameter and the function contains a keyword variadic parameter dictionary. It may be surprising behaviour when the keyword argument is added to the keyword variadic parameter dictionary. Closes #8558 (#8558 \) ### Extensions - • Add new **prefer-typing-namedtuple** message to the **CodeStyleChecker** to suggest rewriting calls to **collections.namedtuple** as classes inheriting from **typing.NamedTuple** on Python 3.6+. Requires **load-plugins=pylint.extensions.code\_style** and **enable=prefer-typing-namedtuple** to be raised. Closes #8660 (#8660 \) ### False Positives Fixed - • Extend concept of "function ambiguity" in **safe\_infer()** from differing number of function arguments to differing set of argument names. Solves false positives in **tensorflow**. Closes #3613 (#3613 \) - • Fix *unused-argument* false positive when *\_\_new\_\_* does not use all the arguments of *\_\_init\_\_*. Closes #3670 (#3670 \) - • Fix a false positive for **invalid-name** when a type-annotated class variable in an **enum.Enum** class has no assigned value. Refs #7402 (#7402 \) - • Fix **unused-import** false positive for usage of **six.with\_metaclass**. Closes #7506 (#7506 \) - • Fix false negatives and false positives for **too-many-try-statements**, **too-complex**, and **too-many-branches** by correctly counting statements under a **try**. Refs #7767 (#7767 \) - • When checking for unbalanced dict unpacking in for-loops, Pylint will now test whether the length of each value to be unpacked matches the number of unpacking targets. Previously, Pylint would test the number of values for the loop iteration, which would produce a false unbalanced-dict-unpacking / W0644 \<#unbalanced-dict-unpacking\> warning. Closes #8156 (#8156 \) - • Fix false positive for **used-before-assignment** when usage and assignment are guarded by the same test in different statements. Closes #8167 (#8167 \) - • Adds **asyncSetUp** to the default **defining-attr-methods** list to silence **attribute-defined-outside-init** warning when using **unittest.IsolatedAsyncioTestCase**. Refs #8403 (#8403 \) - • *logging-not-lazy* is not longer emitted for explicitly concatenated string arguments. Closes #8410 (#8410 \) - • Fix false positive for isinstance-second-argument-not-valid-type / W1116 \<#isinstance-second-argument-not-valid-type\> when union types contains None. Closes #8424 (#8424 \) - • **invalid-name** now allows for integers in **typealias** names: - now valid: **Good2Name**, **GoodName2**. - still invalid: **\_1BadName**. Closes #8485 (#8485 \) - • No longer consider **Union** as type annotation as type alias for naming checks. Closes #8487 (#8487 \) - • **unnecessary-lambda** no longer warns on lambdas which use its parameters in their body (other than the final arguments), e.g. **lambda foo: (bar if foo else baz)(foo)**. Closes #8496 (#8496 \) - • Fixed *unused-import* so that it observes the *dummy-variables-rgx* option. Closes #8500 (#8500 \) - • *Union* typed variables without assignment are no longer treated as *TypeAlias*. Closes #8540 (#8540 \) - • Allow parenthesized implicitly concatenated strings when *check-str-concat-over-line-jumps* is enabled. Closes #8552. (#8552 \) - • Fix false positive for **positional-only-arguments-expected** when a function contains both a positional-only parameter that has a default value, and **\*\*kwargs**. Closes #8555 (#8555 \) - • Fix false positive for **keyword-arg-before-vararg** when a positional-only parameter with a default value precedes **\*args**. Closes #8570 (#8570 \) - • Fix false positive for **arguments-differ** when overriding *\_\_init\_subclass\_\_*. Closes #8919 (#8919 \) - • Fix a false positive for **no-value-for-parameter** when a staticmethod is called in a class body. Closes #9036 (#9036 \) ### False Negatives Fixed - • Emit **used-before-assignment** when calling module-level functions before definition. Closes #1144 (#1144 \) - • Apply **infer\_kwarg\_from\_call()** to more checks These mostly solve false negatives for various checks, save for one false positive for **use-maxsplit-arg**. Closes #7761 (#7761 \) - • *TypeAlias* variables defined in functions are now checked for *invalid-name* errors. Closes #8536 (#8536 \) - • Fix false negative for **no-value-for-parameter** when a function, whose signature contains both a positional-only parameter **name** and also **\*kwargs**, is called with a keyword-argument for **name**. Closes #8559 (#8559 \) - • Fix a false negative for **too-many-arguments** by considering positional-only and keyword-only parameters. Closes #8667 (#8667 \) - • Emit **assignment-from-no-return** for calls to builtin methods like **dict.update()**. Calls to **list.sort()** now raise **assignment-from-no-return** rather than **assignment-from-none** for consistency. Closes #8714 Closes #8810 (#8714 \) - • **consider-using-augmented-assign** is now applied to dicts and lists as well. Closes #8959. (#8959 \) ### Other Bug Fixes - • Support **duplicate-code** message when parallelizing with **--jobs**. Closes #374 (#374 \) - • Support **cyclic-import** message when parallelizing with **--jobs**. Closes #4171 (#4171 \) - • **--jobs** can now be used with **--load-plugins**. This had regressed in astroid 2.5.0. Closes #4874 (#4874 \) - • docparams extension considers type comments as type documentation. Closes #6287 (#6287 \) - • When parsing comma-separated lists of regular expressions in the config, ignore commas that are inside braces since those indicate quantifiers, not delineation between expressions. Closes #7229 (#7229 \) - • The **ignored-modules** option will now be correctly taken into account for **no-name-in-module**. Closes #7578 (#7578 \) - • **sys.argv** is now always correctly considered as impossible to infer (instead of using the actual values given to pylint). Closes #7710 (#7710 \) - • Avoid duplicative warnings for unqualified exception names in the **overgeneral-exceptions** setting when running with **--jobs**. Closes #7774 (#7774 \) - • Don't show class fields more than once in Pyreverse diagrams. Closes #8189 (#8189 \) - • Fix **used-before-assignment** false negative when TYPE\_CHECKING imports are used in multiple scopes. Closes #8198 (#8198 \) - • **--clear-cache-post-run** now also clears LRU caches for pylint utilities holding references to AST nodes. Closes #8361 (#8361 \) - • Fix a crash when **TYPE\_CHECKING** is used without importing it. Closes #8434 (#8434 \) - • Fix a **used-before-assignment** false positive when imports are made under the **TYPE\_CHECKING** else if branch. Closes #8437 (#8437 \) - • Fix a regression of **preferred-modules** where a partial match was used instead of the required full match. Closes #8453 (#8453 \) - • Fix a crash in pyreverse when "/" characters are used in the output filename e.g pyreverse -o png -p name/ path/to/project. Closes #8504 (#8504 \) - • Don't show arrows more than once in Pyreverse diagrams. Closes #8522 (#8522 \) - • Improve output of **consider-using-generator** message for **min()** calls with **default** keyword. Closes #8563 (#8563 \) - • Fixed a crash when generating a configuration file: **tomlkit.exceptions.TOMLKitError: Can't add a table to a dotted key** caused by tomlkit **v0.11.8**. Closes #8632 (#8632 \) - • Fix a line break error in Pyreverse dot output. Closes #8671 (#8671 \) - • Fix a false positive for **method-hidden** when using **cached\_property** decorator. Closes #8753 (#8753 \) - • Dunder methods defined in lambda do not trigger **unnecessary-dunder-call** anymore, if they cannot be replaced by the non-dunder call. Closes #8769 (#8769 \) - • Don't show duplicate type annotations in Pyreverse diagrams. Closes #8888 (#8888 \) - • Fixing inconsistent hashing issue in *BaseChecker* causing some reports not being exported. Closes #9001 (#9001 \) - • Don't add *Optional* to *\|* annotations with *None* in Pyreverse diagrams. Closes #9014 (#9014 \) - • Pyreverse doesn't show multiple class association arrows anymore, but only the strongest one. Refs #9045 (#9045 \) - • Prevented data loss in the linter stats for messages relating to the linter itself (e.g. **unknown-option-value**), fixing problems with score, fail-on, etc. Closes #9059 (#9059 \) - • Fix crash in refactoring checker when unary operand used with variable in for loop. Closes #9074 (#9074 \) ### Other Changes - • Pylint now exposes its type annotations. Closes #5488 and #2079 (#5488 \) - • Search for **pyproject.toml** recursively in parent directories up to a project or file system root. Refs #7163, Closes #3289 (#7163 \) - • All code related to the optparse config parsing has been removed. Refs #8405 (#8405 \) - • Pylint now supports python 3.12. Refs #8718 (#8718 \) - • Add a CITATION.cff file to the root of the repository containing the necessary metadata to cite Pylint. Closes #8760 (#8760 \) - • Renamed the "unneeded-not / C0113 \<#unneeded-not\>" error into "unnecessary\_negation" to be clearer. Closes #8789 (#8789 \) ### Internal Changes - • **get\_message\_definition** was removed from the base checker API. You can access message definitions through the **MessageStore**. Refs #8401 (#8401 \) - • Everything related to the **\_\_implements\_\_** construct was removed. It was based on PEP245 that was proposed in 2001 and rejected in 2006. All the classes inheriting **Interface** in **pylint.interfaces** were removed. **Checker** should only inherit **BaseChecker** or any of the other checker types from **pylint.checkers**. **Reporter** should only inherit **BaseReporter**. Refs #8404 (#8404 \) - • **modname** and **msg\_store** are now required to be given in **FileState**. **collect\_block\_lines** has also been removed. **Pylinter.current\_name** cannot be null anymore. Refs #8407 (#8407 \) - • **Reporter.set\_output** was removed in favor of **reporter.out = stream**. Refs #8408 (#8408 \) - • A number of old utility functions and classes have been removed: **MapReduceMixin**: To make a checker reduce map data simply implement **get\_map\_data** and **reduce\_map\_data**. **is\_inside\_lambda**: Use **utils.get\_node\_first\_ancestor\_of\_type(x, nodes.Lambda)** **check\_messages**: Use **utils.only\_required\_for\_messages** **is\_class\_subscriptable\_pep585\_with\_postponed\_evaluation\_enabled**: Use **is\_postponed\_evaluation\_enabled(node)** and **is\_node\_in\_type\_annotation\_context(node)** **get\_python\_path**: assumption that there's always an \_\_init\_\_.py is not true since python 3.3 and is causing problems, particularly with PEP 420. Use **discover\_package\_path** and pass source root(s). **fix\_import\_path**: Use **augmented\_sys\_path** and pass additional **sys.path** entries as an argument obtained from **discover\_package\_path**. **get\_global\_option**: Use **checker.linter.config** to get all global options. Related private objects have been removed as well. Refs #8409 (#8409 \) - • **colorize\_ansi** now only accepts a **MessageStyle** object. Refs #8412 (#8412 \) - • Following a deprecation period, **Pylinter.check** now only works with sequences of strings, not strings. Refs #8463 (#8463 \) - • Following a deprecation period, **ColorizedTextReporter** only accepts **ColorMappingDict**. Refs #8464 (#8464 \) - • Following a deprecation period, **MessageTest**'s **end\_line** and **end\_col\_offset** must be accurate in functional tests (for python 3.8 or above on cpython, and for python 3.9 or superior on pypy). Refs #8466 (#8466 \) - • Following a deprecation period, the **do\_exit** argument of the **Run** class (and of the **\_Run** class in testutils) were removed. Refs #8472 (#8472 \) - • Following a deprecation period, the **py\_version** argument of the **MessageDefinition.may\_be\_emitted** function is now required. The most likely solution is to use 'linter.config.py\_version' if you need to keep using this function, or to use 'MessageDefinition.is\_message\_enabled' instead. Refs #8473 (#8473 \) - • Following a deprecation period, the **OutputLine** class now requires the right number of argument all the time. The functional output can be regenerated automatically to achieve that easily. Refs #8474 (#8474 \) - • Following a deprecation period, **is\_typing\_guard**, **is\_node\_in\_typing\_guarded\_import\_block** and **is\_node\_in\_guarded\_import\_block** from **pylint.utils** were removed: use a combination of **is\_sys\_guard** and **in\_type\_checking\_block** instead. Refs #8475 (#8475 \) - • Following a deprecation period, the **location** argument of the **Message** class must now be a **MessageLocationTuple**. Refs #8477 (#8477 \) - • Following a deprecation period, the **check\_single\_file** function of the **Pylinter** is replaced by **Pylinter.check\_single\_file\_item**. Refs #8478 (#8478 \) ### Performance Improvements - • **pylint** runs (at least) ~5% faster after improvements to **astroid** that make better use of the inference cache. Refs pylint-dev/astroid#529 (#529 \) - • - • Optimize **is\_trailing\_comma()**. - • Cache **class\_is\_abstract()**. Refs #1954 (#1954 \) - • Exit immediately if all messages are disabled. Closes #8715 (#8715 \) ### 2.x From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### What's New in Pylint 2.17 - **Release** 2\.17 - **Date** 2023-03-08 ### Summary -- Release highlights 2\.17 is a small release that is the first to support python 3.11 officially with the addition of TryStar nodes. There's still two new default checks: **bad-chained-comparison** and **implicit-flag-alias**, one of them already fixed a previously undetected bug in sentry. Thanks to the community effort our documentation is almost complete, and every messages should have a proper documentation now. A big thank you to everyone who participated ! The next release is going to be **3.0.0**, bring breaking changes and enact long announced deprecations. There's going to be frequent beta releases, before the official releases, everyone is welcome to try the betas so we find problems before the actual release. ### What's new in Pylint 2.17.7? Release date: 2023-09-30 ### False Positives Fixed - • Fix a regression in pylint 2.17.6 / astroid 2.15.7 causing various messages for code involving **TypeVar**. Closes #9069 (#9069 \) ### Other Bug Fixes - • Fix crash in refactoring checker when unary operand used with variable in for loop. Closes #9074 (#9074 \) ### What's new in Pylint 2.17.6? Release date: 2023-09-24 ### Other Bug Fixes - • When parsing comma-separated lists of regular expressions in the config, ignore commas that are inside braces since those indicate quantifiers, not delineation between expressions. Closes #7229 (#7229 \) - • **sys.argv** is now always correctly considered as impossible to infer (instead of using the actual values given to pylint). Closes #7710 (#7710 \) - • Don't show class fields more than once in Pyreverse diagrams. Closes #8189 (#8189 \) - • Don't show arrows more than once in Pyreverse diagrams. Closes #8522 (#8522 \) - • Don't show duplicate type annotations in Pyreverse diagrams. Closes #8888 (#8888 \) - • Don't add *Optional* to *\|* annotations with *None* in Pyreverse diagrams. Closes #9014 (#9014 \) ### What's new in Pylint 2.17.5? Release date: 2023-07-26 ### False Positives Fixed - • Fix a false positive for **unused-variable** when there is an import in a **if TYPE\_CHECKING:** block and **allow-global-unused-variables** is set to **no** in the configuration. Closes #8696 (#8696 \) - • Fix false positives generated when supplying arguments as **\*\*kwargs** to IO calls like open(). Closes #8719 (#8719 \) - • Fix a false positive where pylint was ignoring method calls annotated as **NoReturn** during the **inconsistent-return-statements** check. Closes #8747 (#8747 \) - • Exempt parents with only type annotations from the **invalid-enum-extension** message. Closes #8830 (#8830 \) ### Other Bug Fixes - • Fixed crash when a call to **super()** was placed after an operator (e.g. **not**). Closes #8554 (#8554 \) - • Fix crash for **modified-while-iterating** checker when deleting members of a dict returned from a call. Closes #8598 (#8598 \) - • Fix crash in **invalid-metaclass** check when a metaclass had duplicate bases. Closes #8698 (#8698 \) - • Avoid **consider-using-f-string** on modulos with brackets in template. Closes #8720. (#8720 \) - • Fix a crash when **\_\_all\_\_** exists but cannot be inferred. Closes #8740 (#8740 \) - • Fix crash when a variable is assigned to a class attribute of identical name. Closes #8754 (#8754 \) - • Fixed a crash when calling **copy.copy()** without arguments. Closes #8774 (#8774 \) ### Other Changes - • Fix a crash when a **nonlocal** is defined at module-level. Closes #8735 (#8735 \) ### What's new in Pylint 2.17.4? Release date: 2023-05-06 ### False Positives Fixed - • Fix a false positive for **bad-dunder-name** when there is a user-defined **\_\_index\_\_** method. Closes #8613 (#8613 \) ### Other Bug Fixes - • **pyreverse**: added escaping of vertical bar character in annotation labels produced by DOT printer to ensure it is not treated as field separator of record-based nodes. Closes #8603 (#8603 \) - • Fixed a crash when generating a configuration file: **tomlkit.exceptions.TOMLKitError: Can't add a table to a dotted key** caused by tomlkit **v0.11.8**. Closes #8632 (#8632 \) ### What's new in Pylint 2.17.3? Release date: 2023-04-24 ### False Positives Fixed - • Fix *unused-argument* false positive when *\_\_new\_\_* does not use all the arguments of *\_\_init\_\_*. Closes #3670 (#3670 \) - • Fix **unused-import** false positive for usage of **six.with\_metaclass**. Closes #7506 (#7506 \) - • *logging-not-lazy* is not longer emitted for explicitly concatenated string arguments. Closes #8410 (#8410 \) - • Fix false positive for isinstance-second-argument-not-valid-type / W1116 \<#isinstance-second-argument-not-valid-type\> when union types contains None. Closes #8424 (#8424 \) - • Fixed *unused-import* so that it observes the *dummy-variables-rgx* option. Closes #8500 (#8500 \) - • *Union* typed variables without assignment are no longer treated as *TypeAlias*. Closes #8540 (#8540 \) - • Fix false positive for **positional-only-arguments-expected** when a function contains both a positional-only parameter that has a default value, and **\*\*kwargs**. Closes #8555 (#8555 \) - • Fix false positive for **keyword-arg-before-vararg** when a positional-only parameter with a default value precedes **\*args**. Closes #8570 (#8570 \) ### Other Bug Fixes - • Improve output of **consider-using-generator** message for **min()** calls with **default** keyword. Closes #8563 (#8563 \) ### What's new in Pylint 2.17.2? Release date: 2023-04-03 ### False Positives Fixed - • **invalid-name** now allows for integers in **typealias** names: - now valid: **Good2Name**, **GoodName2**. - still invalid: **\_1BadName**. Closes #8485 (#8485 \) - • No longer consider **Union** as type annotation as type alias for naming checks. Closes #8487 (#8487 \) - • **unnecessary-lambda** no longer warns on lambdas which use its parameters in their body (other than the final arguments), e.g. **lambda foo: (bar if foo else baz)(foo)**. Closes #8496 (#8496 \) ### Other Bug Fixes - • Fix a crash in pyreverse when "/" characters are used in the output filename e.g pyreverse -o png -p name/ path/to/project. Closes #8504 (#8504 \) ### What's new in Pylint 2.17.1? Release date: 2023-03-22 ### False Positives Fixed - • Adds **asyncSetUp** to the default **defining-attr-methods** list to silence **attribute-defined-outside-init** warning when using **unittest.IsolatedAsyncioTestCase**. Refs #8403 (#8403 \) ### Other Bug Fixes - • **--clear-cache-post-run** now also clears LRU caches for pylint utilities holding references to AST nodes. Closes #8361 (#8361 \) - • Fix a crash when **TYPE\_CHECKING** is used without importing it. Closes #8434 (#8434 \) - • Fix a regression of **preferred-modules** where a partial match was used instead of the required full match. Closes #8453 (#8453 \) ### Internal Changes - • The following utilities are deprecated in favor of the more robust **in\_type\_checking\_block** and will be removed in pylint 3.0: - • **is\_node\_in\_guarded\_import\_block** - • **is\_node\_in\_typing\_guarded\_import\_block** - • **is\_typing\_guard** **is\_sys\_guard** is still available, which was part of **is\_node\_in\_guarded\_import\_block**. Refs #8433 (#8433 \) ### What's new in Pylint 2.17.0? Release date: 2023-03-08 ### New Features - • *pyreverse* now supports custom color palettes with the *--color-palette* option. Closes #6738 (#6738 \) - • Add **invalid-name** check for **TypeAlias** names. Closes #7081. (#7081 \) - • Accept values of the form **\.\** for the **exclude-protected** list. Closes #7343 (#7343 \) - • Add *--version* option to *pyreverse*. Refs #7851 (#7851 \) - • Adds new functionality with preferred-modules configuration to detect submodules. Refs #7957 (#7957 \) - • Support implicit namespace packages (PEP 420). Closes #8154 (#8154 \) - • Add globbing pattern support for **--source-roots**. Closes #8290 (#8290 \) - • Support globbing pattern when defining which file/directory/module to lint. Closes #8310 (#8310 \) - • pylint now supports **TryStar** nodes from Python 3.11 and should be fully compatible with Python 3.11. Closes #8387 (#8387 \) ### New Checks - • Add a **bad-chained-comparison** check that emits a warning when there is a chained comparison where one expression is semantically incompatible with the other. Closes #6559 (#6559 \) - • Adds an **implicit-flag-alias** check that emits a warning when a class derived from **enum.IntFlag** assigns distinct integer values that share common bit positions. Refs #8102 (#8102 \) ### False Positives Fixed - • Fix various false positives for functions that return directly from structural pattern matching cases. Closes #5288 (#5288 \) - • Fix false positive for **used-before-assignment** when **typing.TYPE\_CHECKING** is used with if/elif/else blocks. Closes #7574 (#7574 \) - • Fix false positive for isinstance-second-argument-not-valid-type / W1116 \<#isinstance-second-argument-not-valid-type\> with union types. Closes #8205 (#8205 \) - • Fix false positive for **used-before-assignment** for named expressions appearing after the first element in a list, tuple, or set. Closes #8252 (#8252 \) - • Fix false positive for **wrong-spelling-in-comment** with class names in a python 2 type comment. Closes #8370 (#8370 \) ### False Negatives Fixed - • Fix a false negative for missing-parentheses-for-call-in-test / W0126 \<#missing-parentheses-for-call-in-test\>' when inference failed for the internal of the call as we did not need that information to raise correctly. Refs #8185 (#8185 \) - • Fix false negative for inconsistent-returns with while-loops. Closes #8280 (#8280 \) ### Other Bug Fixes - • Fix **used-before-assignment** false positive when the walrus operator is used with a ternary operator in dictionary key/value initialization. Closes #8125 (#8125 \) - • Fix **no-name-in-module** false positive raised when a package defines a variable with the same name as one of its submodules. Closes #8148 (#8148 \) - • Fix a crash happening for python interpreter \< 3.9 following a failed typing update. Closes #8161 (#8161 \) - • Fix **nested-min-max** suggestion message to indicate it's possible to splat iterable objects. Closes #8168 (#8168 \) - • Fix a crash happening when a class attribute was negated in the start argument of an enumerate. Closes #8207 (#8207 \) - • Prevent emitting **invalid-name** for the line on which a **global** statement is declared. Closes #8307 (#8307 \) ### Other Changes - • Update explanation for **global-variable-not-assigned** and add confidence. Closes #5073 (#5073 \) - • The governance model and the path to become a maintainer have been documented as part of our effort to guarantee that the software supply chain in which pylint is included is secure. Refs #8329 (#8329 \) ### What's New in Pylint 2.16 - **Release** 2\.16 - **Date** 2023-02-01 ### Summary -- Release highlights In 2.16.0 we added aggregation and composition understanding in **pyreverse**, and a way to clear the cache in between run in server mode (originally for the VS Code integration). Apart from the bug fixes there's also a lot of new checks, and new extensions that have been asked for for a long time that were implemented. If you want to benefit from all the new checks load the following plugins: ``` pylint.extensions.dict_init_mutate, pylint.extensions.dunder, pylint.extensions.typing, pylint.extensions.magic_value, ``` We still welcome any community effort to help review, integrate, and add good/bad examples to the doc for \<\\>\`\_. This should be doable without any **pylint** or **astroid** knowledge, so this is the perfect entrypoint if you want to contribute to **pylint** or open source without any experience with our code! Last but not least @clavedeluna and @nickdrozd became triagers, welcome to the team ! ### What's new in Pylint 2.16.4? Release date: 2023-03-06 ### False Positives Fixed - • Fix false positive for isinstance-second-argument-not-valid-type / W1116 \<#isinstance-second-argument-not-valid-type\> with union types. Closes #8205 (#8205 \) ### What's new in Pylint 2.16.3? Release date: 2023-03-03 ### False Positives Fixed - • Fix false positive for **wrong-spelling-in-comment** with class names in a python 2 type comment. Closes #8370 (#8370 \) ### Other Bug Fixes - • Prevent emitting **invalid-name** for the line on which a **global** statement is declared. Closes #8307 (#8307 \) ### What's new in Pylint 2.16.2? Release date: 2023-02-13 ### New Features - • Add *--version* option to *pyreverse*. Refs #7851 (#7851 \) ### False Positives Fixed - • Fix false positive for **used-before-assignment** when **typing.TYPE\_CHECKING** is used with if/elif/else blocks. Closes #7574 (#7574 \) - • Fix false positive for **used-before-assignment** for named expressions appearing after the first element in a list, tuple, or set. Closes #8252 (#8252 \) ### Other Bug Fixes - • Fix **used-before-assignment** false positive when the walrus operator is used with a ternary operator in dictionary key/value initialization. Closes #8125 (#8125 \) - • Fix **no-name-in-module** false positive raised when a package defines a variable with the same name as one of its submodules. Closes #8148 (#8148 \) - • Fix **nested-min-max** suggestion message to indicate it's possible to splat iterable objects. Closes #8168 (#8168 \) - • Fix a crash happening when a class attribute was negated in the start argument of an enumerate. Closes #8207 (#8207 \) ### What's new in Pylint 2.16.1? Release date: 2023-02-02 ### Other Bug Fixes - • Fix a crash happening for python interpreter \< 3.9 following a failed typing update. Closes #8161 (#8161 \) ### What's new in Pylint 2.16.0? Release date: 2023-02-01 ### Changes requiring user actions - • The **accept-no-raise-doc** option related to **missing-raises-doc** will now be correctly taken into account all the time. Pylint will no longer raise missing-raises-doc / W9006 \<#missing-raises-doc\> (W9006) when no exceptions are documented and accept-no-raise-doc is true (issue #7208). If you were expecting missing-raises-doc / W9006 \<#missing-raises-doc\> errors to be raised in that case, you will now have to add **accept-no-raise-doc=no** in your configuration to keep the same behavior. Closes #7208 (#7208 \) ### New Features - • Added the **no-header** output format. If enabled with **--output-format=no-header**, it will not include the module name in the output. Closes #5362 (#5362 \) - • Added configuration option **clear-cache-post-run** to support server-like usage. Use this flag if you expect the linted files to be altered between runs. Refs #5401 (#5401 \) - • Add **--allow-reexport-from-package** option to configure the **useless-import-alias** check not to emit a warning if a name is reexported from a package. Closes #6006 (#6006 \) - • Update **pyreverse** to differentiate between aggregations and compositions. **pyreverse** checks if it's an Instance or a Call of an object via method parameters (via type hints) to decide if it's a composition or an aggregation. Refs #6543 (#6543 \) ### New Checks - • Adds a **pointless-exception-statement** check that emits a warning when an Exception is created and not assigned, raised or returned. Refs #3110 (#3110 \) - • Add a **shadowed-import** message for aliased imports. Closes #4836 (#4836 \) - • Add new check called **unbalanced-dict-unpacking** to check for unbalanced dict unpacking in assignment and for loops. Closes #5797 (#5797 \) - • Add new checker **positional-only-arguments-expected** to check for cases when positional-only arguments have been passed as keyword arguments. Closes #6489 (#6489 \) - • Added **singledispatch-method** which informs that **@singledispatch** should decorate functions and not class/instance methods. Added **singledispatchmethod-function** which informs that **@singledispatchmethod** should decorate class/instance methods and not functions. Closes #6917 (#6917 \) - • Rename **broad-except** to **broad-exception-caught** and add new checker **broad-exception-raised** which will warn if general exceptions **BaseException** or **Exception** are raised. Closes #7494 (#7494 \) - • Added **nested-min-max** which flags **min(1, min(2, 3))** to simplify to **min(1, 2, 3)**. Closes #7546 (#7546 \) - • Extended **use-dict-literal** to also warn about call to **dict()** when passing keyword arguments. Closes #7690 (#7690 \) - • Add **named-expr-without-context** check to emit a warning if a named expression is used outside a context like **if**, **for**, **while**, or a comprehension. Refs #7760 (#7760 \) - • Add **invalid-slice-step** check to warn about a slice step value of **0** for common builtin sequences. Refs #7762 (#7762 \) - • Add **consider-refactoring-into-while-condition** check to recommend refactoring when a while loop is defined with a constant condition with an immediate **if** statement to check for **break** condition as a first statement. Closes #8015 (#8015 \) ### Extensions - • Add new extension checker **dict-init-mutate** that flags mutating a dictionary immediately after the dictionary was created. Closes #2876 (#2876 \) - • Added **bad-dunder-name** extension check, which flags bad or misspelled dunder methods. You can use the **good-dunder-names** option to allow specific dunder names. Closes #3038 (#3038 \) - • Added **consider-using-augmented-assign** check for **CodeStyle** extension which flags **x = x + 1** to simplify to **x += 1**. This check is disabled by default. To use it, load the code style extension with **load-plugins=pylint.extensions.code\_style** and add **consider-using-augmented-assign** in the **enable** option. Closes #3391 (#3391 \) - • Add **magic-number** plugin checker for comparison with constants instead of named constants or enums. You can use it with **--load-plugins=pylint.extensions.magic\_value**. Closes #7281 (#7281 \) - • Add **redundant-typehint-argument** message for *typing* plugin for duplicate assign typehints. Enable the plugin to enable the message with: **--load-plugins=pylint.extensions.typing**. Closes #7636 (#7636 \) ### False Positives Fixed - • Fix false positive for **unused-variable** and **unused-import** when a name is only used in a string literal type annotation. Closes #3299 (#3299 \) - • Document a known false positive for **useless-suppression** when disabling **line-too-long** in a module with only comments and no code. Closes #3368 (#3368 \) - • **trailing-whitespaces** is no longer reported within strings. Closes #3822 (#3822 \) - • Fix false positive for **global-variable-not-assigned** when a global variable is re-assigned via an **ImportFrom** node. Closes #4809 (#4809 \) - • Fix false positive for **use-maxsplit-arg** with custom split method. Closes #4857 (#4857 \) - • Fix **logging-fstring-interpolation** false positive raised when logging and f-string with **%s** formatting. Closes #4984 (#4984 \) - • Fix false-positive for **used-before-assignment** in pattern matching with a guard. Closes #5327 (#5327 \) - • Fix **use-sequence-for-iteration** when unpacking a set with **\***. Closes #5788 (#5788 \) - • Fix **deprecated-method** false positive when alias for method is similar to name of deprecated method. Closes #5886 (#5886 \) - • Fix false positive **assigning-non-slot** when a class attribute is re-assigned. Closes #6001 (#6001 \) - • Fix false positive for **too-many-function-args** when a function call is assigned to a class attribute inside the class where the function is defined. Closes #6592 (#6592 \) - • Fixes false positive **abstract-method** on Protocol classes. Closes #7209 (#7209 \) - • Pylint now understands the **kw\_only** keyword argument for **dataclass**. Closes #7290, closes #6550, closes #5857 (#7290 \) - • Fix false positive for **undefined-loop-variable** in **for-else** loops that use a function having a return type annotation of **NoReturn** or **Never**. Closes #7311 (#7311 \) - • Fix **used-before-assignment** for functions/classes defined in type checking guard. Closes #7368 (#7368 \) - • Fix false positive for **unhashable-member** when subclassing **dict** and using the subclass as a dictionary key. Closes #7501 (#7501 \) - • Fix the message for **unnecessary-dunder-call** for **\_\_aiter\_\_** and **\_\_aneext\_\_**. Also only emit the warning when **py-version** \>= 3.10. Closes #7529 (#7529 \) - • Fix **used-before-assignment** false positive when else branch calls **sys.exit** or similar terminating functions. Closes #7563 (#7563 \) - • Fix a false positive for **used-before-assignment** for imports guarded by **typing.TYPE\_CHECKING** later used in variable annotations. Closes #7609 (#7609 \) - • Fix a false positive for **simplify-boolean-expression** when multiple values are inferred for a constant. Closes #7626 (#7626 \) - • **unnecessary-list-index-lookup** will not be wrongly emitted if **enumerate** is called with **start**. Closes #7682 (#7682 \) - • Don't warn about **stop-iteration-return** when using **next()** over **itertools.cycle**. Closes #7765 (#7765 \) - • Fixes **used-before-assignment** false positive when the walrus operator is used in a ternary operator. Closes #7779 (#7779 \) - • Fix **missing-param-doc** false positive when function parameter has an escaped underscore. Closes #7827 (#7827 \) - • Fixes **method-cache-max-size-none** false positive for methods inheriting from **Enum**. Closes #7857 (#7857 \) - • **multiple-statements** no longer triggers for function stubs using inlined **...**. Closes #7860 (#7860 \) - • Fix a false positive for **used-before-assignment** when a name guarded by **if TYPE\_CHECKING:** is used as a type annotation in a function body and later re-imported in the same scope. Closes #7882 (#7882 \) - • Prevent **used-before-assignment** when imports guarded by **if** **TYPE\_CHECKING** are guarded again when used. Closes #7979 (#7979 \) - • Fixes false positive for **try-except-raise** with multiple exceptions in one except statement if exception are in different namespace. Closes #8051 (#8051 \) - • Fix **invalid-name** errors for **typing\_extension.TypeVar**. Refs #8089 (#8089 \) - • Fix **no-kwoa** false positive for context managers. Closes #8100 (#8100 \) - • Fix a false positive for **redefined-variable-type** when **async** methods are present. Closes #8120 (#8120 \) ### False Negatives Fixed - • Code following a call to **quit**, **exit**, **sys.exit** or **os.\_exit** will be marked as *unreachable*. Refs #519 (#519 \) - • Emit **used-before-assignment** when function arguments are redefined inside an inner function and accessed there before assignment. Closes #2374 (#2374 \) - • Fix a false negative for **unused-import** when one module used an import in a type annotation that was also used in another module. Closes #4150 (#4150 \) - • Flag **superfluous-parens** if parentheses are used during string concatenation. Closes #4792 (#4792 \) - • Emit **used-before-assignment** when relying on names only defined under conditions always testing false. Closes #4913 (#4913 \) - • **consider-using-join** can now be emitted for non-empty string separators. Closes #6639 (#6639 \) - • Emit **used-before-assignment** for further imports guarded by **TYPE\_CHECKING** Previously, this message was only emitted for imports guarded directly under **TYPE\_CHECKING**, not guarded two if-branches deep, nor when **TYPE\_CHECKING** was imported from **typing** under an alias. Closes #7539 (#7539 \) - • Fix a false negative for **unused-import** when a constant inside **typing.Annotated** was treated as a reference to an import. Closes #7547 (#7547 \) - • **consider-using-any-or-all** message will now be raised in cases when boolean is initialized, reassigned during loop, and immediately returned. Closes #7699 (#7699 \) - • Extend **invalid-slice-index** to emit an warning for invalid slice indices used with string and byte sequences, and range objects. Refs #7762 (#7762 \) - • Fixes **unnecessary-list-index-lookup** false negative when **enumerate** is called with **iterable** as a kwarg. Closes #7770 (#7770 \) - • **no-else-return** or **no-else-raise** will be emitted if **except** block always returns or raises. Closes #7788 (#7788 \) - • Fix **dangerous-default-value** false negative when **\*** is used. Closes #7818 (#7818 \) - • **consider-using-with** now triggers for **pathlib.Path.open**. Closes #7964 (#7964 \) ### Other Bug Fixes - • Fix bug in detecting **unused-variable** when iterating on variable. Closes #3044 (#3044 \) - • Fix bug in scanning of names inside arguments to **typing.Literal**. See \ for details. Refs #3299 (#3299 \) - • Update **disallowed-name** check to flag module-level variables. Closes #3701 (#3701 \) - • Pylint will no longer deadlock if a parallel job is killed but fail immediately instead. Closes #3899 (#3899 \) - • Fix ignored files being linted when passed on stdin. Closes #4354 (#4354 \) - • Fix **no-member** false negative when augmented assign is done manually, without **+=**. Closes #4562 (#4562 \) - • Any assertion on a populated tuple will now receive a **assert-on-tuple** warning. Closes #4655 (#4655 \) - • **missing-return-doc**, **missing-raises-doc** and **missing-yields-doc** now respect the **no-docstring-rgx** option. Closes #4743 (#4743 \) - • Update **reimported** help message for clarity. Closes #4836 (#4836 \) - • **consider-iterating-dictionary** will no longer be raised if bitwise operations are used. Closes #5478 (#5478 \) - • Using custom braces in **msg-template** will now work properly. Closes #5636 (#5636 \) - • Pylint will now filter duplicates given to it before linting. The output should be the same whether a file is given/discovered multiple times or not. Closes #6242, #4053 (#6242 \) - • Remove **\_\_index\_\_** dunder method call from **unnecessary-dunder-call** check. Closes #6795 (#6795 \) - • Fixed handling of **--** as separator between positional arguments and flags. This was not actually fixed in 2.14.5. Closes #7003, Refs #7096 (#7003 \) - • Don't crash on **OSError** in config file discovery. Closes #7169 (#7169 \) - • Messages sent to reporter are now copied so a reporter cannot modify the message sent to other reporters. Closes #7214 (#7214 \) - • Fixed a case where custom plugins specified by command line could silently fail. Specifically, if a plugin relies on the **init-hook** option changing **sys.path** before it can be imported, this will now emit a **bad-plugin-value** message. Before this change, it would silently fail to register the plugin for use, but would load any configuration, which could have unintended effects. Fixes part of #7264. (#7264 \) - • Update **modified\_iterating** checker to fix a crash with **for** loops on empty list. Closes #7380 (#7380 \) - • Update wording for **arguments-differ** and **arguments-renamed** to clarify overriding object. Closes #7390 (#7390 \) - • **disable-next** is now correctly scoped to only the succeeding line. Closes #7401 (#7401 \) - • Fixed a crash in the **unhashable-member** checker when using a **lambda** as a dict key. Closes #7453 (#7453 \) - • Add **mailcap** to deprecated modules list. Closes #7457 (#7457 \) - • Fix a crash in the **modified-iterating-dict** checker involving instance attributes. Closes #7461 (#7461 \) - • **invalid-class-object** does not crash anymore when **\_\_class\_\_** is assigned alongside another variable. Closes #7467 (#7467 \) - • **--help-msg** now accepts a comma-separated list of message IDs again. Closes #7471 (#7471 \) - • Allow specifying non-builtin exceptions in the **overgeneral-exception** option using an exception's qualified name. Closes #7495 (#7495 \) - • Report **no-self-argument** rather than **no-method-argument** for methods with variadic arguments. Closes #7507 (#7507 \) - • Fixed an issue where **syntax-error** couldn't be raised on files with invalid encodings. Closes #7522 (#7522 \) - • Fix false positive for **redefined-outer-name** when aliasing **typing** e.g. as **t** and guarding imports under **t.TYPE\_CHECKING**. Closes #7524 (#7524 \) - • Fixed a crash of the **modified\_iterating** checker when iterating on a set defined as a class attribute. Closes #7528 (#7528 \) - • Use **py-version** to determine if a message should be emitted for messages defined with **max-version** or **min-version**. Closes #7569 (#7569 \) - • Improve **bad-thread-instantiation** check to warn if **target** is not passed in as a keyword argument or as a second argument. Closes #7570 (#7570 \) - • Fixes edge case of custom method named **next** raised an astroid error. Closes #7610 (#7610 \) - • Fixed a multi-processing crash that prevents using any more than 1 thread on MacOS. The returned module objects and errors that were cached by the linter plugin loader cannot be reliably pickled. This means that **dill** would throw an error when attempting to serialise the linter object for multi-processing use. Closes #7635. (#7635 \) - • Fix crash that happened when parsing files with unexpected encoding starting with 'utf' like **utf13**. Closes #7661 (#7661 \) - • Fix a crash when a child class with an **\_\_init\_\_** method inherits from a parent class with an **\_\_init\_\_** class attribute. Closes #7742 (#7742 \) - • Fix **valid-metaclass-classmethod-first-arg** default config value from "cls" to "mcs" which would cause both a false-positive and false-negative. Closes #7782 (#7782 \) - • Fixes a crash in the **unnecessary\_list\_index\_lookup** check when using **enumerate** with **start** and a class attribute. Closes #7821 (#7821 \) - • Fixes a crash in **stop-iteration-return** when the **next** builtin is called without arguments. Closes #7828 (#7828 \) - • When pylint exit due to bad arguments being provided the exit code will now be the expected **32**. Refs #7931 (#7931 \) - • Fixes a **ModuleNotFound** exception when running pylint on a Django project with the **pylint\_django** plugin enabled. Closes #7938 (#7938 \) - • Fixed a crash when inferring a value and using its qname on a slice that was being incorrectly called. Closes #8067 (#8067 \) - • Use better regex to check for private attributes. Refs #8081 (#8081 \) - • Fix issue with new typing Union syntax in runtime context for Python 3.10+. Closes #8119 (#8119 \) ### Other Changes - • Pylint now provides basic support for Python 3.11. Closes #5920 (#5920 \) - • Update message for **abstract-method** to include child class name. Closes #7124 (#7124 \) - • Update Pyreverse's dot and plantuml printers to detect when class methods are abstract and show them with italic font. For the dot printer update the label to use html-like syntax. Closes #7346 (#7346 \) - • The **docparams** extension now considers typing in Numpy style docstrings as "documentation" for the **missing-param-doc** message. Refs #7398 (#7398 \) - • Relevant **DeprecationWarnings** are now raised with **stacklevel=2**, so they have the callsite attached in the message. Closes #7463 (#7463 \) - • Add a **minimal** option to **pylint-config** and its toml generator. Closes #7485 (#7485 \) - • Add method name to the error messages of **no-method-argument** and **no-self-argument**. Closes #7507 (#7507 \) - • Prevent leaving the pip install cache in the Docker image. Refs #7544 (#7544 \) - • Add a keyword-only **compare\_constants** argument to **safe\_infer**. Refs #7626 (#7626 \) - • Add **default\_enabled** option to optional message dict. Provides an option to disable a checker message by default. To use a disabled message, the user must enable it explicitly by adding the message to the **enable** option. Refs #7629 (#7629 \) - • Sort **--generated-rcfile** output. Refs #7655 (#7655 \) - • epylint is now deprecated and will be removed in pylint 3.0.0. All emacs and flymake related files were removed and their support will now happen in an external repository : \. Closes #7737 (#7737 \) - • Adds test for existing preferred-modules configuration functionality. Refs #7957 (#7957 \) ### Internal Changes - • Add and fix regression tests for plugin loading. This shores up the tests that cover the loading of custom plugins as affected by any changes made to the **sys.path** during execution of an **init-hook**. Given the existing contract of allowing plugins to be loaded by fiddling with the path in this way, this is now the last bit of work needed to close Github issue #7264. Closes #7264 (#7264 \) ### What's New in Pylint 2.15 - **Release** 2\.15 - **Date** 2022-08-26 ### Summary -- Release highlights In pylint 2.15.0, we added a new check **missing-timeout** to warn of default timeout values that could cause a program to be hanging indefinitely. We improved **pylint**'s handling of namespace packages. More packages should be linted without resorting to using the **--recursive=y** option. We still welcome any community effort to help review, integrate, and add good/bad examples to the doc for \<\\>\`\_. This should be doable without any **pylint** or **astroid** knowledge, so this is the perfect entrypoint if you want to contribute to **pylint** or open source without any experience with our code! Internally, we changed the way we generate the release notes, thanks to DudeNr33. There will be no more conflict resolution to do in the changelog, and every contributor rejoice. Marc Byrne became a maintainer, welcome to the team ! ### What's new in Pylint 2.15.10? Release date: 2023-01-09 ### False Positives Fixed - • Fix **use-sequence-for-iteration** when unpacking a set with **\***. Closes #5788 (#5788 \) - • Fix false positive **assigning-non-slot** when a class attribute is re-assigned. Closes #6001 (#6001 \) - • Fixes **used-before-assignment** false positive when the walrus operator is used in a ternary operator. Closes #7779 (#7779 \) - • Prevent **used-before-assignment** when imports guarded by **if** **TYPE\_CHECKING** are guarded again when used. Closes #7979 (#7979 \) ### Other Bug Fixes - • Using custom braces in **msg-template** will now work properly. Closes #5636 (#5636 \) ### What's new in Pylint 2.15.9? Release date: 2022-12-17 ### False Positives Fixed - • Fix false-positive for **used-before-assignment** in pattern matching with a guard. Closes #5327 (#5327 \) ### Other Bug Fixes - • Pylint will no longer deadlock if a parallel job is killed but fail immediately instead. Closes #3899 (#3899 \) - • When pylint exit due to bad arguments being provided the exit code will now be the expected **32**. Refs #7931 (#7931 \) - • Fixes a **ModuleNotFound** exception when running pylint on a Django project with the **pylint\_django** plugin enabled. Closes #7938 (#7938 \) ### What's new in Pylint 2.15.8? Release date: 2022-12-05 ### False Positives Fixed - • Document a known false positive for **useless-suppression** when disabling **line-too-long** in a module with only comments and no code. Closes #3368 (#3368 \) - • Fix **logging-fstring-interpolation** false positive raised when logging and f-string with **%s** formatting. Closes #4984 (#4984 \) - • Fixes false positive **abstract-method** on Protocol classes. Closes #7209 (#7209 \) - • Fix **missing-param-doc** false positive when function parameter has an escaped underscore. Closes #7827 (#7827 \) - • **multiple-statements** no longer triggers for function stubs using inlined **...**. Closes #7860 (#7860 \) ### What's new in Pylint 2.15.7? Release date: 2022-11-27 ### False Positives Fixed - • Fix **deprecated-method** false positive when alias for method is similar to name of deprecated method. Closes #5886 (#5886 \) - • Fix a false positive for **used-before-assignment** for imports guarded by **typing.TYPE\_CHECKING** later used in variable annotations. Closes #7609 (#7609 \) ### Other Bug Fixes - • Pylint will now filter duplicates given to it before linting. The output should be the same whether a file is given/discovered multiple times or not. Closes #6242, #4053 (#6242 \) - • Fixes a crash in **stop-iteration-return** when the **next** builtin is called without arguments. Closes #7828 (#7828 \) ### What's new in Pylint 2.15.6? Release date: 2022-11-19 ### False Positives Fixed - • Fix false positive for **unhashable-member** when subclassing **dict** and using the subclass as a dictionary key. Closes #7501 (#7501 \) - • **unnecessary-list-index-lookup** will not be wrongly emitted if **enumerate** is called with **start**. Closes #7682 (#7682 \) - • Don't warn about **stop-iteration-return** when using **next()** over **itertools.cycle**. Closes #7765 (#7765 \) ### Other Bug Fixes - • Messages sent to reporter are now copied so a reporter cannot modify the message sent to other reporters. Closes #7214 (#7214 \) - • Fixes edge case of custom method named **next** raised an astroid error. Closes #7610 (#7610 \) - • Fix crash that happened when parsing files with unexpected encoding starting with 'utf' like **utf13**. Closes #7661 (#7661 \) - • Fix a crash when a child class with an **\_\_init\_\_** method inherits from a parent class with an **\_\_init\_\_** class attribute. Closes #7742 (#7742 \) ### What's new in Pylint 2.15.5? Release date: 2022-10-21 ### False Positives Fixed - • Fix a false positive for **simplify-boolean-expression** when multiple values are inferred for a constant. Closes #7626 (#7626 \) ### Other Bug Fixes - • Remove **\_\_index\_\_** dunder method call from **unnecessary-dunder-call** check. Closes #6795 (#6795 \) - • Fixed a multi-processing crash that prevents using any more than 1 thread on MacOS. The returned module objects and errors that were cached by the linter plugin loader cannot be reliably pickled. This means that **dill** would throw an error when attempting to serialise the linter object for multi-processing use. Closes #7635. (#7635 \) ### Other Changes - • Add a keyword-only **compare\_constants** argument to **safe\_infer**. Refs #7626 (#7626 \) - • Sort **--generated-rcfile** output. Refs #7655 (#7655 \) ### What's new in Pylint 2.15.4? Release date: 2022-10-10 ### False Positives Fixed - • Fix the message for **unnecessary-dunder-call** for **\_\_aiter\_\_** and **\_\_anext\_\_**. Also only emit the warning when **py-version** \>= 3.10. Closes #7529 (#7529 \) ### Other Bug Fixes - • Fix bug in detecting **unused-variable** when iterating on variable. Closes #3044 (#3044 \) - • Fixed handling of **--** as separator between positional arguments and flags. This was not actually fixed in 2.14.5. Closes #7003, Refs #7096 (#7003 \) - • Report **no-self-argument** rather than **no-method-argument** for methods with variadic arguments. Closes #7507 (#7507 \) - • Fixed an issue where **syntax-error** couldn't be raised on files with invalid encodings. Closes #7522 (#7522 \) - • Fix false positive for **redefined-outer-name** when aliasing **typing** e.g. as **t** and guarding imports under **t.TYPE\_CHECKING**. Closes #7524 (#7524 \) - • Fixed a crash of the **modified\_iterating** checker when iterating on a set defined as a class attribute. Closes #7528 (#7528 \) - • Fix bug in scanning of names inside arguments to **typing.Literal**. See \ for details. Refs #3299 (#3299 \) ### Other Changes - • Add method name to the error messages of **no-method-argument** and **no-self-argument**. Closes #7507 (#7507 \) ### What's new in Pylint 2.15.3? Release date: 2022-09-19 - • Fixed a crash in the **unhashable-member** checker when using a **lambda** as a dict key. Closes #7453 (#7453 \) - • Fix a crash in the **modified-iterating-dict** checker involving instance attributes. Closes #7461 (#7461 \) - • **invalid-class-object** does not crash anymore when **\_\_class\_\_** is assigned alongside another variable. Closes #7467 (#7467 \) - • Fix false positive for **global-variable-not-assigned** when a global variable is re-assigned via an **ImportFrom** node. Closes #4809 (#4809 \) - • Fix false positive for **undefined-loop-variable** in **for-else** loops that use a function having a return type annotation of **NoReturn** or **Never**. Closes #7311 (#7311 \) - • **--help-msg** now accepts a comma-separated list of message IDs again. Closes #7471 (#7471 \) ### What's new in Pylint 2.15.2? Release date: 2022-09-07 - • Fixed a case where custom plugins specified by command line could silently fail. Specifically, if a plugin relies on the **init-hook** option changing **sys.path** before it can be imported, this will now emit a **bad-plugin-value** message. Before this change, it would silently fail to register the plugin for use, but would load any configuration, which could have unintended effects. Fixes part of #7264. (#7264 \) - • Fix **used-before-assignment** for functions/classes defined in type checking guard. Closes #7368 (#7368 \) - • Update **modified\_iterating** checker to fix a crash with **for** loops on empty list. Closes #7380 (#7380 \) - • The **docparams** extension now considers typing in Numpy style docstrings as "documentation" for the **missing-param-doc** message. Refs #7398 (#7398 \) - • Fix false positive for **unused-variable** and **unused-import** when a name is only used in a string literal type annotation. Closes #3299 (#3299 \) - • Fix false positive for **too-many-function-args** when a function call is assigned to a class attribute inside the class where the function is defined. Closes #6592 (#6592 \) - • Fix ignored files being linted when passed on stdin. Closes #4354 (#4354 \) - • **missing-return-doc**, **missing-raises-doc** and **missing-yields-doc** now respect the **no-docstring-rgx** option. Closes #4743 (#4743 \) - • Don't crash on **OSError** in config file discovery. Closes #7169 (#7169 \) - • **disable-next** is now correctly scoped to only the succeeding line. Closes #7401 (#7401 \) - • Update **modified\_iterating** checker to fix a crash with **for** loops on empty list. Closes #7380 (#7380 \) ### What's new in Pylint 2.15.1? Release date: 2022-09-06 This is a "github only release", it was mistakenly released as **2.16.0-dev** on pypi. Replaced by **2.15.2**. ### What's new in Pylint 2.15.0? ### New Checks - • Added new checker **missing-timeout** to warn of default timeout values that could cause a program to be hanging indefinitely. Refs #6780 (#6780 \) ### False Positives Fixed - • Don't report **super-init-not-called** for abstract **\_\_init\_\_** methods. Closes #3975 (#3975 \) - • Don't report **unsupported-binary-operation** on Python \<= 3.9 when using the **\|** operator with types, if one has a metaclass that overloads **\_\_or\_\_** or **\_\_ror\_\_** as appropriate. Closes #4951 (#4951 \) - • Don't report **no-value-for-parameter** for dataclasses fields annotated with **KW\_ONLY**. Closes #5767 (#5767 \) - • Fixed inference of **Enums** when they are imported under an alias. Closes #5776 (#5776 \) - • Prevent false positives when accessing **PurePath.parents** by index (not slice) on Python 3.10+. Closes #5832 (#5832 \) - • **unnecessary-list-index-lookup** is now more conservative to avoid potential false positives. Closes #6896 (#6896 \) - • Fix double emitting **trailing-whitespace** for multi-line docstrings. Closes #6936 (#6936 \) - • **import-error** now correctly checks for **contextlib.suppress** guards on import statements. Closes #7270 (#7270 \) - • Fix false positive for *no-self-argument*/*no-method-argument* when a staticmethod is applied to a function but uses a different name. Closes #7300 (#7300 \) - • Fix *undefined-loop-variable* with *break* and *continue* statements in *else* blocks. Refs #7311 (#7311 \) - • Improve default TypeVar name regex. Disallow names prefixed with **T**. E.g. use **AnyStrT** instead of **TAnyStr**. Refs #7322 (*#7322 \\`\_*) ### False Negatives Fixed - • Emit **used-before-assignment** when relying on a name that is reimported later in a function. Closes #4624 (#4624 \) - • Emit **used-before-assignment** for self-referencing named expressions (**:=**) lacking prior assignments. Closes #5653 (#5653 \) - • Emit **used-before-assignment** for self-referencing assignments under if conditions. Closes #6643 (#6643 \) - • Emit **modified-iterating-list** and analogous messages for dicts and sets when iterating literals, or when using the **del** keyword. Closes #6648 (#6648 \) - • Emit **used-before-assignment** when calling nested functions before assignment. Closes #6812 (#6812 \) - • Emit **nonlocal-without-binding** when a nonlocal name has been assigned at a later point in the same scope. Closes #6883 (#6883 \) - • Emit **using-constant-test** when testing the truth value of a variable or call result holding a generator. Closes #6909 (#6909 \) - • Rename **unhashable-dict-key** to **unhashable-member** and emit when creating sets and dicts, not just when accessing dicts. Closes #7034, Closes #7055 (#7034 \) ### Other Bug Fixes - • Fix a failure to lint packages with **\_\_init\_\_.py** contained in directories lacking **\_\_init\_\_.py**. Closes #1667 (#1667 \) - • Fixed a syntax-error / E0001 \<#syntax-error\> crash that was not handled properly when the declared encoding of a file was **utf-9**. Closes #3860 (#3860 \) - • Fix a crash in the **not-callable** check when there is ambiguity whether an instance is being incorrectly provided to **\_\_new\_\_()**. Closes #7109 (#7109 \) - • Fix crash when regex option raises a *re.error* exception. Closes #7202 (#7202 \) - • Fix *undefined-loop-variable* from walrus in comprehension test. Closes #7222 (#7222 \) - • Check for *\* before removing first item from *sys.path* in *modify\_sys\_path*. Closes #7231 (#7231 \) - • Fix sys.path pollution in parallel mode. Closes #7246 (#7246 \) - • Prevent *useless-parent-delegation* for delegating to a builtin written in C (e.g. *Exception.\_\_init\_\_*) with non-self arguments. Closes #7319 (#7319 \) ### Other Changes - • **bad-exception-context** has been renamed to **bad-exception-cause** as it is about the cause and not the context. Closes #3694 (#3694 \) - • The message for **literal-comparison** is now more explicit about the problem and the solution. Closes #5237 (#5237 \) - • **useless-super-delegation** has been renamed to **useless-parent-delegation** in order to be more generic. Closes #6953 (#6953 \) - • Pylint now uses **towncrier** for changelog generation. Refs #6974 (#6974 \) - • Update **astroid** to 2.12. Refs #7153 (#7153 \) - • Fix crash when a type-annotated *\_\_slots\_\_* with no value is declared. Closes #7280 (#7280 \) ### Internal Changes - • Fixed an issue where it was impossible to update functional tests output when the existing output was impossible to parse. Instead of raising an error we raise a warning message and let the functional test fail with a default value. Refs #6891 (#6891 \) - • **pylint.testutils.primer** is now a private API. Refs #6905 (#6905 \) - • We changed the way we handle the changelog internally by using towncrier. If you're a contributor you won't have to fix merge conflicts in the changelog anymore. Closes #6974 (#6974 \) - • Pylint is now using Scorecards to implement security recommendations from the OpenSSF \. This is done in order to secure our supply chains using a combination of automated tooling and best practices, most of which were already implemented before. Refs #7267 (#7267 \) ### What's New in Pylint 2.14 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights With 2.14 **pylint** only supports Python version 3.7.2 and above. We introduced several new checks among which **duplicate-value** for sets, **comparison-of-constants**, and checks related to lambdas. We removed **no-init** and made **no-self-use** optional as they were too opinionated. We also added an option to generate a toml configuration: **--generate-toml-config**. We migrated to **argparse** from **optparse** and refactored the configuration handling thanks to Daniël van Noord. On the user side it should change the output of the **--help** command, and some inconsistencies and bugs should disappear. The behavior between options set in a config file versus on the command line will be more consistent. For us, it will permit to maintain this part of the code easily in the future. As a result of the refactor there are a lot of internal deprecations. If you're a library maintainer that depends on pylint, please verify that you're ready for pylint 3.0 by activating deprecation warnings. We continued the integration of **pylint-error** and are now at 33%!. We still welcome any community effort to help review, integrate, and add good/bad examples \<\\>\`\_. This should be doable without any **pylint** or **astroid** knowledge, so this is the perfect entrypoint if you want to contribute to **pylint** or open source without any experience with our code! ### New checkers - • Added new checker **comparison-of-constants**. Closes #6076 - • Added new checker **typevar-name-mismatch**: TypeVar must be assigned to a variable with the same name as its name argument. Closes #5224 - • **invalid-enum-extension**: Used when a class tries to extend an inherited Enum class. Closes #5501 - • Added new checker **typevar-double-variance**: The "covariant" and "contravariant" keyword arguments cannot both be set to "True" in a TypeVar. Closes #5895 - • Add new check **unnecessary-dunder-call** for unnecessary dunder method calls. Closes #5936 - • **unnecessary-lambda-assignment**: Lambda expression assigned to a variable. Define a function using the "def" keyword instead. **unnecessary-direct-lambda-call**: Lambda expression called directly. Execute the expression inline instead. Closes #5976 - • **potential-index-error**: Emitted when the index of a list or tuple exceeds its length. This checker is currently quite conservative to avoid false positives. We welcome suggestions for improvements. Closes #578 - • Added new checker **unnecessary-list-index-lookup** for indexing into a list while iterating over **enumerate()**. Closes #4525 - • Added new message called **duplicate-value** which identifies duplicate values inside sets. Closes #5880 - • Added the **super-without-brackets** checker, raised when a super call is missing its brackets. Closes #4008 ### Removed checkers - • The **no-init** (W0232) warning has been removed. It's ok to not have an **\_\_init\_\_** in a class. Closes #2409 - • Removed the **assign-to-new-keyword** message as there are no new keywords in the supported Python versions any longer. Closes #4683 - • Moved **no-self-use** check to optional extension. You now need to explicitly enable this check using **load-plugins=pylint.extensions.no\_self\_use**. Closes #5502 ### Extensions - • **RedefinedLoopNameChecker** - • Added optional extension **redefined-loop-name** to emit messages when a loop variable is redefined in the loop body. Closes #5072 - • **DocStringStyleChecker** - • Re-enable checker **bad-docstring-quotes** for Python \<= 3.7. Closes #6087 - • **NoSelfUseChecker** - • Added **no-self-use** check, previously enabled by default. Closes #5502 ### Other Changes - • Started ignoring underscore as a local variable for **too-many-locals**. Closes #6488 - • Pylint can now be installed with an extra-require called **spelling** (**pip install pylint\[spelling\]**). This will add **pyenchant** to pylint's dependencies. You will still need to install the requirements for **pyenchant** (the **enchant** library and any dictionaries) yourself. You will also need to set the **spelling-dict** option. Refs #6462 - • Improved wording of the message of **deprecated-module** Closes #6169 - • **Pylint** now requires Python 3.7.2 or newer to run. Closes #4301 - • We made a greater effort to reraise failures stemming from the **astroid** library as **AstroidError**, with the effect that pylint emits **astroid-error** rather than merely **fatal**. Regardless, please report any such issues you encounter! - • We have improved our recognition of inline disable and enable comments. It is now possible to disable **bad-option-value** inline (as long as you disable it before the bad option value is raised, i.e. **disable=bad-option-value,bad-message** not **disable=bad-message,bad-option-value** ) as well as certain other previously unsupported messages. Closes #3312 - • The main checker name is now **main** instead of **master**. The configuration does not need to be updated as sections' name are optional. Closes #5467 - • Update **invalid-slots-object** message to show bad object rather than its inferred value. Closes #6101 - • Fixed a crash in the **not-an-iterable** checker involving multiple starred expressions inside a call. Closes #6372 - • Fixed a crash in the **unused-private-member** checker involving chained private attributes. Closes #6709 - • Disable spellchecking of mypy rule names in ignore directives. Closes #5929 - • **implicit-str-concat** will now be raised on calls like **open("myfile.txt" "a+b")** too. Closes #6441 - • Fix a failure to respect inline disables for **fixme** occurring on the last line of a module when pylint is launched with **--enable=fixme**. - • Removed the broken **generate-man** option. Closes #5283 Closes #1887 - • Fixed failure to enable **deprecated-module** after a **disable=all** by making **ImportsChecker** solely responsible for emitting **deprecated-module** instead of sharing responsibility with **StdlibChecker**. (This could have led to double messages.) - • Added the **generate-toml-config** option. Refs #5462 - • **bad-option-value** will be emitted whenever a configuration value or command line invocation includes an unknown message. Closes #4324 - • Added the **unrecognized-option** message. Raised if we encounter any unrecognized options. Closes #5259 - • Fix false negative for **bad-string-format-type** if the value to be formatted is passed in as a variable holding a constant. - • The concept of checker priority has been removed. - • The **cache-max-size-none** checker has been renamed to **method-cache-max-size-none**. Closes #5670 - • The **method-cache-max-size-none** checker will now also check **functools.cache**. Closes #5670 - • **BaseChecker** classes now require the **linter** argument to be passed. - • The **set\_config\_directly** decorator has been removed. - • Don't report **useless-super-delegation** for the **\_\_hash\_\_** method in classes that also override the **\_\_eq\_\_** method. Closes #3934 - • Fix falsely issuing **useless-suppression** on the **wrong-import-position** checker. Closes #5219 - • Fixed false positive **no-member** for Enums with self-defined members. Closes #5138 - • Fix false negative for **no-member** when attempting to assign an instance attribute to itself without any prior assignment. Closes #1555 - • Changed message type from **redefined-outer-name** to **redefined-loop-name** (optional extension) for redefinitions of outer loop variables by inner loops. Closes #5608 - • By default the similarity checker will now ignore imports and ignore function signatures when computing duplication. If you want to keep the previous behaviour set **ignore-imports** and **ignore-signatures** to **False**. - • Pylint now expands the user path (i.e. **~** to **home/yusef/**) and expands environment variables (i.e. **home/$USER/$project** to **home/yusef/pylint** for **USER=yusef** and **project=pylint**) for pyreverse's **output-directory**, **import-graph**, **ext-import-graph**, **int-import-graph** options, and the spell checker's **spelling-private-dict-file** option. Refs #6493 - • Don't emit **unsubscriptable-object** for string annotations. Pylint doesn't check if class is only generic in type stubs only. Closes #4369 and #6523 - • Fix pyreverse crash **RuntimeError: dictionary changed size during iteration** Refs #6612 - • Fix syntax for return type annotations in MermaidJS diagrams produced with **pyreverse**. Closes #6467 - • Fix type annotations of class and instance attributes using the alternative union syntax in **pyreverse** diagrams. - • Fix bug where it writes a plain text error message to stdout, invalidating output formats. Closes #6597 - • The refactoring checker now also raises 'consider-using-a-generator' messages for **max()**, **min()** and **sum()**. Refs #6595 - • Update ranges for **using-constant-test** and **missing-parentheses-for-call-in-test** error messages. - • Don't emit **no-member** inside type annotations with **from \_\_future\_\_ import annotations**. Closes #6594 - • Fix **unexpected-special-method-signature** false positive for **\_\_init\_subclass\_\_** methods with one or more arguments. Closes #6644 ### Deprecations - • The **ignore-mixin-members** option has been deprecated. You should now use the new **ignored-checks-for-mixins** option. Closes #5205 - • **interfaces.implements** has been deprecated and will be removed in 3.0. Please use standard inheritance patterns instead of **\_\_implements\_\_**. Refs #2287 - • All **Interface** classes in **pylint.interfaces** have been deprecated. You can subclass the respective normal classes to get the same behaviour. The **\_\_implements\_\_** functionality was based on a rejected PEP from 2001: \ Closes #2287 - • **MapReduceMixin** has been deprecated. **BaseChecker** now implements **get\_map\_data** and **reduce\_map\_data**. If a checker actually needs to reduce data it should define **get\_map\_data** as returning something different than **None** and let its **reduce\_map\_data** handle a list of the types returned by **get\_map\_data**. An example can be seen by looking at **pylint/checkers/similar.py**. - • The **config** attribute of **BaseChecker** has been deprecated. You can use **checker.linter.config** to access the global configuration object instead of a checker-specific object. Refs #5392 - • The **level** attribute of **BaseChecker** has been deprecated: everything is now displayed in **--help**, all the time. Refs #5392 - • The **set\_option** method of **BaseChecker** has been deprecated. You can use **checker.linter.set\_option** to set an option on the global configuration object instead of a checker-specific object. Refs #5392 - • The **options\_providers** attribute of **ArgumentsManager** has been deprecated. Refs #5392 - • Fix saving of persistent data files in environments where the user's cache directory and the linted file are on a different drive. Closes #6394 - • The **method-cache-max-size-none** checker will now also check **functools.cache**. - • The **config** attribute of **PyLinter** is now of the **argparse.Namespace** type instead of **optparse.Values**. Refs #5392 - • **UnsupportedAction** has been deprecated. Refs #5392 - • **OptionsManagerMixIn** has been deprecated. Refs #5392 - • **OptionParser** has been deprecated. Refs #5392 - • **Option** has been deprecated. Refs #5392 - • **OptionsProviderMixIn** has been deprecated. Refs #5392 - • **ConfigurationMixIn** has been deprecated. - • The **option\_groups** attribute of **PyLinter** has been deprecated. Refs #5392 - • **get\_global\_config** has been deprecated. You can now access all global options from **checker.linter.config**. Refs #5392 - • **OptionsManagerMixIn** has been replaced with **ArgumentsManager**. **ArgumentsManager** is considered private API and most methods that were public on **OptionsManagerMixIn** have now been deprecated and will be removed in a future release. Refs #5392 - • **OptionsProviderMixIn** has been replaced with **ArgumentsProvider**. **ArgumentsProvider** is considered private API and most methods that were public on **OptionsProviderMixIn** have now been deprecated and will be removed in a future release. Refs #5392 - • **pylint.pyreverse.ASTWalker** has been removed, as it was only used internally by a single child class. Refs #6712 - • **pyreverse**: Resolving and displaying implemented interfaces that are defined by the **\_\_implements\_\_** attribute has been deprecated and will be removed in 3.0. Refs #6713 - • **is\_class\_subscriptable\_pep585\_with\_postponed\_evaluation\_enabled** has been deprecated. Use **is\_postponed\_evaluation\_enabled(node) and is\_node\_in\_type\_annotation\_context(node)** instead. Refs #6536 ### Full changelog ### What's New in Pylint 2.14.5? Release date: 2022-07-17 - • Fixed a crash in the **undefined-loop-variable** check when **enumerate()** is used in a ternary expression. Closes #7131 - • Fixed handling of **--** as separator between positional arguments and flags. Closes #7003 - • Fixed the disabling of **fixme** and its interaction with **useless-suppression**. - • Allow lists of default values in parameter documentation for **Numpy** style. Closes #4035 ### What's New in Pylint 2.14.4? Release date: 2022-06-29 - • The **differing-param-doc** check was triggered by positional only arguments. Closes #6950 - • Fixed an issue where scanning *.* directory recursively with **--ignore-path=^path/to/dir** is not ignoring the *path/to/dir* directory. Closes #6964 - • Fixed regression that didn't allow quoted **init-hooks** in option files. Closes #7006 - • Fixed a false positive for **modified-iterating-dict** when updating an existing key. Closes #6179 - • Fixed an issue where many-core Windows machines (\>~60 logical processors) would hang when using the default jobs count. Closes #6965 - • Fixed an issue with the recognition of **setup.cfg** files. Only **.cfg** files that are exactly named **setup.cfg** require section names that start with **pylint.**. Closes #3630 - • Don't report **import-private-name** for relative imports. Closes #7078 ### What's New in Pylint 2.14.3? Release date: 2022-06-18 - • Fixed two false positives for **bad-super-call** for calls that refer to a non-direct parent. Closes #4922, Closes #2903 - • Fixed a false positive for **useless-super-delegation** for subclasses that specify the number of of parameters against a parent that uses a variadic argument. Closes #2270 - • Allow suppressing **undefined-loop-variable** and **undefined-variable** without raising **useless-suppression**. - • Fixed false positive for **undefined-variable** for **\_\_class\_\_** in inner methods. Closes #4032 ### What's New in Pylint 2.14.2? Release date: 2022-06-15 - • Fixed a false positive for **unused-variable** when a function returns an **argparse.Namespace** object. Closes #6895 - • Avoided raising an identical **undefined-loop-variable** message twice on the same line. - • Don't crash if **lint.run.\_query\_cpu()** is run within a Kubernetes Pod, that has only a fraction of a cpu core assigned. Just go with one process then. Closes #6902 - • Fixed a false positive in **consider-using-f-string** if the left side of a **%** is not a string. Closes #6689 - • Fixed a false positive in **unnecessary-list-index-lookup** and **unnecessary-dict-index-lookup** when the subscript is updated in the body of a nested loop. Closes #6818 - • Fixed an issue with multi-line **init-hook** options which did not record the line endings. Closes #6888 - • Fixed a false positive for **used-before-assignment** when a try block returns but an except handler defines a name via type annotation. - • **--errors-only** no longer enables previously disabled messages. It was acting as "emit *all* and only error messages" without being clearly documented that way. Closes #6811 ### What's New in Pylint 2.14.1? Release date: 2022-06-06 - • Avoid reporting **unnecessary-dict-index-lookup** or **unnecessary-list-index-lookup** when the index lookup is part of a destructuring assignment. Closes #6788 - • Fixed parsing of unrelated options in **tox.ini**. Closes #6800 - • Fixed a crash when linting **\_\_new\_\_()** methods that return a call expression. Closes #6805 - • Don't crash if we can't find the user's home directory. Closes #6802 - • Fixed false positives for **unused-import** when aliasing **typing** e.g. as **t** and guarding imports under **t.TYPE\_CHECKING**. Closes #3846 - • Fixed a false positive regression in 2.13 for **used-before-assignment** where it is safe to rely on a name defined only in an **except** block because the **else** block returned. Closes #6790 - • Fixed the use of abbreviations for some special options on the command line. Closes #6810 - • Fix a crash in the optional **pylint.extensions.private\_import** extension. Closes #6624 - • **bad-option-value** (E0012) is now a warning **unknown-option-value** (W0012). Deleted messages that do not exist anymore in pylint now raise **useless-option-value** (R0022) instead of **bad-option-value**. This allows to distinguish between genuine typos and configuration that could be cleaned up. Existing message disables for **bad-option-value** will still work on both new messages. Refs #6794 ### What's New in Pylint 2.14.0? Release date: 2022-06-01 - • The refactoring checker now also raises consider-using-generator / R1728 \<#consider-using-generator\>' messages for **max()**, **min()** and **sum()**. Refs #6595 - • We have improved our recognition of inline disable and enable comments. It is now possible to disable **bad-option-value** inline (as long as you disable it before the bad option value is raised, i.e. **disable=bad-option-value,bad-message** not **disable=bad-message,bad-option-value** ) as well as certain other previously unsupported messages. Closes #3312 - • Fixed a crash in the **unused-private-member** checker involving chained private attributes. Closes #6709 - • Added new checker **comparison-of-constants**. Closes #6076 - • **pylint.pyreverse.ASTWalker** has been removed, as it was only used internally by a single child class. Refs #6712 - • **pyreverse**: Resolving and displaying implemented interfaces that are defined by the **\_\_implements\_\_** attribute has been deprecated and will be removed in 3.0. Refs #6713 - • Fix syntax for return type annotations in MermaidJS diagrams produced with **pyreverse**. Closes #6467 - • Fix type annotations of class and instance attributes using the alternative union syntax in **pyreverse** diagrams. - • Fix **unexpected-special-method-signature** false positive for **\_\_init\_subclass\_\_** methods with one or more arguments. Closes #6644 - • Started ignoring underscore as a local variable for **too-many-locals**. Closes #6488 - • Improved wording of the message of **deprecated-module** Closes #6169 - • **Pylint** now requires Python 3.7.2 or newer to run. Closes #4301 - • **BaseChecker** classes now require the **linter** argument to be passed. - • Fix a failure to respect inline disables for **fixme** occurring on the last line of a module when pylint is launched with **--enable=fixme**. - • Update **invalid-slots-object** message to show bad object rather than its inferred value. Closes #6101 - • The main checker name is now **main** instead of **master**. The configuration does not need to be updated as sections' name are optional. Closes #5467 - • Don't report **useless-super-delegation** for the **\_\_hash\_\_** method in classes that also override the **\_\_eq\_\_** method. Closes #3934 - • Added new checker **typevar-name-mismatch**: TypeVar must be assigned to a variable with the same name as its name argument. Closes #5224 - • Pylint can now be installed with an extra-require called **spelling** (**pip install pylint\[spelling\]**). This will add **pyenchant** to pylint's dependencies. You will still need to install the requirements for **pyenchant** (the **enchant** library and any dictionaries) yourself. You will also need to set the **spelling-dict** option. Refs #6462 - • Removed the **assign-to-new-keyword** message as there are no new keywords in the supported Python versions any longer. Closes #4683 - • Fixed a crash in the **not-an-iterable** checker involving multiple starred expressions inside a call. Closes #6372 - • Fixed a crash in the **docparams** extension involving raising the result of a function. - • Fixed failure to enable **deprecated-module** after a **disable=all** by making **ImportsChecker** solely responsible for emitting **deprecated-module** instead of sharing responsibility with **StdlibChecker**. (This could have led to double messages.) - • The **no-init** (W0232) warning has been removed. It's ok to not have an **\_\_init\_\_** in a class. Closes #2409 - • The **config** attribute of **BaseChecker** has been deprecated. You can use **checker.linter.config** to access the global configuration object instead of a checker-specific object. Refs #5392 - • The **level** attribute of **BaseChecker** has been deprecated: everything is now displayed in **--help**, all the time. Refs #5392 - • The **options\_providers** attribute of **ArgumentsManager** has been deprecated. Refs #5392 - • The **option\_groups** attribute of **PyLinter** has been deprecated. Refs #5392 - • All **Interface** classes in **pylint.interfaces** have been deprecated. You can subclass the respective normal classes to get the same behaviour. The **\_\_implements\_\_** functionality was based on a rejected PEP from 2001: \ Closes #2287 - • The **set\_option** method of **BaseChecker** has been deprecated. You can use **checker.linter.set\_option** to set an option on the global configuration object instead of a checker-specific object. Refs #5392 - • **implicit-str-concat** will now be raised on calls like **open("myfile.txt" "a+b")** too. Closes #6441 - • The **config** attribute of **PyLinter** is now of the **argparse.Namespace** type instead of **optparse.Values**. Refs #5392 - • **MapReduceMixin** has been deprecated. **BaseChecker** now implements **get\_map\_data** and **reduce\_map\_data**. If a checker actually needs to reduce data it should define **get\_map\_data** as returning something different than **None** and let its **reduce\_map\_data** handle a list of the types returned by **get\_map\_data**. An example can be seen by looking at **pylint/checkers/similar.py**. - • **UnsupportedAction** has been deprecated. Refs #5392 - • **OptionsManagerMixIn** has been deprecated. Refs #5392 - • **OptionParser** has been deprecated. Refs #5392 - • **Option** has been deprecated. Refs #5392 - • **OptionsProviderMixIn** has been deprecated. Refs #5392 - • **ConfigurationMixIn** has been deprecated. Refs #5392 - • **get\_global\_config** has been deprecated. You can now access all global options from **checker.linter.config**. Refs #5392 - • **OptionsManagerMixIn** has been replaced with **ArgumentsManager**. **ArgumentsManager** is considered private API and most methods that were public on **OptionsManagerMixIn** have now been deprecated and will be removed in a future release. Refs #5392 - • **OptionsProviderMixIn** has been replaced with **ArgumentsProvider**. **ArgumentsProvider** is considered private API and most methods that were public on **OptionsProviderMixIn** have now been deprecated and will be removed in a future release. Refs #5392 - • **interfaces.implements** has been deprecated and will be removed in 3.0. Please use standard inheritance patterns instead of **\_\_implements\_\_**. Refs #2287 - • **invalid-enum-extension**: Used when a class tries to extend an inherited Enum class. Closes #5501 - • Added the **unrecognized-option** message. Raised if we encounter any unrecognized options. Closes #5259 - • Added new checker **typevar-double-variance**: The "covariant" and "contravariant" keyword arguments cannot both be set to "True" in a TypeVar. Closes #5895 - • Re-enable checker **bad-docstring-quotes** for Python \<= 3.7. Closes #6087 - • Removed the broken **generate-man** option. Closes #5283 Closes #1887 - • Fix false negative for **bad-string-format-type** if the value to be formatted is passed in as a variable holding a constant. - • Add new check **unnecessary-dunder-call** for unnecessary dunder method calls. Closes #5936 Closes #6074 - • The **cache-max-size-none** checker has been renamed to **method-cache-max-size-none**. Closes #5670 - • The **method-cache-max-size-none** checker will now also check **functools.cache**. Closes #5670 - • **unnecessary-lambda-assignment**: Lambda expression assigned to a variable. Define a function using the "def" keyword instead. **unnecessary-direct-lambda-call**: Lambda expression called directly. Execute the expression inline instead. Closes #5976 - • **potential-index-error**: Emitted when the index of a list or tuple exceeds its length. This checker is currently quite conservative to avoid false positives. We welcome suggestions for improvements. Closes #578 - • Added optional extension **redefined-loop-name** to emit messages when a loop variable is redefined in the loop body. Closes #5072 - • Changed message type from **redefined-outer-name** to **redefined-loop-name** (optional extension) for redefinitions of outer loop variables by inner loops. Closes #5608 - • The **ignore-mixin-members** option has been deprecated. You should now use the new **ignored-checks-for-mixins** option. Closes #5205 - • **bad-option-value** will be emitted whenever a configuration value or command line invocation includes an unknown message. Closes #4324 - • Avoid reporting **superfluous-parens** on expressions using the **is not** operator. Closes #5930 - • Added the **super-without-brackets** checker, raised when a super call is missing its brackets. Closes #4008 - • Added the **generate-toml-config** option. Refs #5462 - • Added new checker **unnecessary-list-index-lookup** for indexing into a list while iterating over **enumerate()**. Closes #4525 - • Fix falsely issuing **useless-suppression** on the **wrong-import-position** checker. Closes #5219 - • Fixed false positive **no-member** for Enums with self-defined members. Closes #5138 - • Fix false negative for **no-member** when attempting to assign an instance attribute to itself without any prior assignment. Closes #1555 - • The concept of checker priority has been removed. - • Add a new command line option **--minimal-messages-config** for **pytest**, which disables all irrelevant messages when running the functional tests. - • **duplicate-argument-name** now only raises once for each set of duplicated arguments. - • Fix bug where specifically enabling just **await-outside-async** was not possible. - • The **set\_config\_directly** decorator has been removed. - • Added new message called **duplicate-value** which identifies duplicate values inside sets. Closes #5880 - • Pylint now expands the user path (i.e. **~** to **home/yusef/**) and expands environment variables (i.e. **home/$USER/$project** to **home/yusef/pylint** for **USER=yusef** and **project=pylint**) for pyreverse's **output-directory**, **import-graph**, **ext-import-graph**, **int-import-graph** options, and the spell checker's **spelling-private-dict-file** option. Refs #6493 - • Created **NoSelfUseChecker** extension and moved the **no-self-use** check. You now need to explicitly enable this check using **load-plugins=pylint.extensions.no\_self\_use**. Closes #5502 - • Fix saving of persistent data files in environments where the user's cache directory and the linted file are on a different drive. Closes #6394 - • Don't emit **unsubscriptable-object** for string annotations. Pylint doesn't check if class is only generic in type stubs only. Closes #4369 and #6523 - • Fix pyreverse crash **RuntimeError: dictionary changed size during iteration** Refs #6612 - • Fix bug where it writes a plain text error message to stdout, invalidating output formats. Closes #6597 - • **is\_class\_subscriptable\_pep585\_with\_postponed\_evaluation\_enabled** has been deprecated. Use **is\_postponed\_evaluation\_enabled(node) and is\_node\_in\_type\_annotation\_context(node)** instead. Refs #6536 - • Update ranges for **using-constant-test** and **missing-parentheses-for-call-in-test** error messages. - • Don't emit **no-member** inside type annotations with **from \_\_future\_\_ import annotations**. Closes #6594 ### What's New in Pylint 2.13 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights In 2.13, we introduced a new check to deal with unicode security issues. On top of that a lot of work was done inside the unicode checker by @CarliJoy. We also introduced a new check when importing private name and for unnecessary ellipsis among other. We fixed long standing issues related to duplicate code that could not be disabled, line numbers that were not accurate some of the time, and added the ability to lint all files in a directory without specifying each one. One of the most anticipated issue from the repository. Thank you @matusvalo ! A lot of **undefined-variables** and **used-before-assignment** issues were resolved thanks to @jacobtylerwalls. We started integrating **pylint-error** the documentation created by @vald-phoenix a developer from Hlyniane, Ukraine. We hope he's doing well despite the current situation. The deployment is set up but there's still a lot to do so we welcome any community effort help to review, integrate, and add good/bad examples \. This should be doable without any pylint or astroid knowledge, so this is the perfect entrypoint if you want to contribute to pylint without investing any time learning the internals. This release is the last one to support interpreter below 3.7.2, 3.6 end of life was reached in december 2021. ### New checkers - • Added several checkers to deal with unicode security issues (see Trojan Sources \ and PEP 672 \ for details) that also concern the readability of the code. In detail the following checks were added: - • **bad-file-encoding** checks that the file is encoded in UTF-8 as suggested by PEP8 \. UTF-16 and UTF-32 are not supported by Python \ at the moment. If this ever changes **invalid-unicode-codec** checks that they aren't used, to allow for backwards compatibility. - • **bidirectional-unicode** checks for bidirectional unicode characters that could make code execution different than what the user expects. - • **invalid-character-backspace**, **invalid-character-carriage-return**, **invalid-character-sub**, **invalid-character-esc**, **invalid-character-zero-width-space** and **invalid-character-nul** to check for possibly harmful unescaped characters. Closes #5281 - • **unnecessary-ellipsis**: Emitted when the ellipsis constant is used unnecessarily. Closes #5460 - • Added new checker **typevar-name-missing-variance**. Emitted when a covariant or contravariant **TypeVar** does not end with **\_co** or **\_contra** respectively or when a **TypeVar** is not either but has a suffix. - • Add **modified-iterating-list**, **modified-iterating-dict**, and **modified-iterating-set**, emitted when items are added to or removed from respectively a list, dictionary or set being iterated through. Closes #5348 - • Add checker **redefined-slots-in-subclass**: Emitted when a slot is redefined in a subclass. Closes #5617 - • - **Rewrote Checker of non-ascii-name.** It now ensures \_\_all\_\_ Python names are ASCII and also properly checks the names of imports (**non-ascii-module-import**) as well as file names (**non-ascii-file-name**) and emits their respective new warnings. Non ASCII characters could be homoglyphs (look alike characters) and hard to enter on a non specialized keyboard. See Confusable Characters in PEP 672 \ - • Added **cache-max-size-none** checker with checks for the use of **functools.lru\_cache** on class methods with a **maxsize** of **None**. This is unrecommended as it creates memory leaks by never letting the instance get garbage collected. Closes #5670 Closes #6180 ### Removed checkers - • Removed the deprecated **check\_docs** extension. You can use the **docparams** checker to get the checks previously included in **check\_docs**. Closes #5322 ### Extensions - • New extension **import-private-name**: indicate imports of external private packages and objects (prefixed with **\_**). It can be loaded using **load-plugins=pylint.extensions.private\_import**. Closes #5463 - • Pyreverse - add output in mermaid-js format and html which is an mermaid js diagram with html boilerplate - • **TypingChecker** - • Added new check **broken-noreturn** to detect broken uses of **typing.NoReturn** if **py-version** is set to Python **3.7.1** or below. \ - • Added new check **broken-collections-callable** to detect broken uses of **collections.abc.Callable** if **py-version** is set to Python **3.9.1** or below. \ - • **DocstringParameterChecker** - • Fixed incorrect classification of Numpy-style docstring as Google-style docstring for docstrings with property setter documentation. Docstring classification is now based on the highest amount of matched sections instead of the order in which the docstring styles were tried. - • **DocStringStyleChecker** - • Disable checker **bad-docstring-quotes** for Python \<= 3.7, because in these versions the line numbers for decorated functions and classes are not reliable which interferes with the checker. Closes #3077 ### Other Changes - • Include **testing\_pylintrc** in source and wheel distributions. Closes #6028 - • Fix false positive for **unused-import** when disabling both **used-before-assignment** and **undefined-variable**. Closes #6089 - • Fix false positive for **unnecessary-ellipsis** when using an ellipsis as a default argument. Closes #5973 - • Add missing dunder methods to **unexpected-special-method-signature** check. - • No longer emit **no-member** in for loops that reference **self** if the binary operation that started the for loop uses a **self** that is encapsulated in tuples or lists. Refs pylint-dev/astroid#1360 Closes #4826 - • Fix matching **--notes** options that end in a non-word character. Closes #5840 - • The line numbering for messages related to function arguments is now more accurate. This can require some message disables to be relocated to updated positions. - • - **using-f-string-in-unsupported-version and using-final-decorator-in-unsupported-version msgids** were renamed from **W1601** and **W1602** to **W2601** and **W2602**. Disables using these msgids will break. This is done in order to restore consistency with the already existing msgids for **apply-builtin** and **basestring-builtin** from the now deleted python 3K+ checker. There is now a check that we're not using existing msgids or symbols from deleted checkers. Closes #5729 - • Add **--recursive** option to allow recursive discovery of all modules and packages in subtree. Running pylint with **--recursive=y** option will check all discovered **.py** files and packages found inside subtree of directory provided as parameter to pylint. Closes #352 - • Updated the position of messages for class and function definitions to no longer cover the complete definition. Only the **def** or **class** + the name of the class/function are covered. Closes #5466 - • Reinstated checks from the python3 checker that are still useful for python 3 (**eq-without-hash**). This is now in the **pylint.extensions.eq\_without\_hash** optional extension. Closes #5025 - • Fix false-negative for **assignment-from-none** checker with list.sort() method. Closes #5722 - • Fix **unused-private-member** false positive when accessing private methods through **property**. Closes #4756 - • Fixed crash from **arguments-differ** and **arguments-renamed** when methods were defined outside the top level of a class. Closes #5648 - • Better warning messages for useless else or elif when a function returns early. Closes #5614 - • Asterisks are no longer required in Sphinx and Google style parameter documentation for **missing-param-doc** and are parsed correctly. Closes #5815 Closes #5406 - • Fixed an **AstroidError** in 2.13.0 raised by the **\`duplicate-code\`** checker with **ignore-imports** or **ignore-signatures** enabled. Closes #6301 - • Use the **tomli** package instead of **toml** to parse **.toml** files. Closes #5885 - • Fixed false positive **consider-using-dict-comprehension** when creating a dict using a list of tuples where key AND value vary depending on the same condition. Closes #5588 - • When run in parallel mode **pylint** now pickles the data passed to subprocesses with the **dill** package. The **dill** package has therefore been added as a dependency. - • Fixed false positive for **global-variable-undefined** when **global** is used with a class name Closes #3088 - • Fixed crash on properties and inherited class methods when comparing them for equality against an empty dict. Closes #5646 - • By default, pylint does no longer take files starting with **.#** into account. Those are considered Emacs file locks \. This behavior can be reverted by redefining the **ignore-patterns** option. Closes #367 - • Fix **super-init-not-called** when parent or **self** is a **Protocol** Closes #4790 - • The issue template for crashes is now created for crashes which were previously not covered by this mechanism. Closes #5668 - • An astroid issue where symlinks were not being taken into account was fixed Closes #1470 Closes #3499 Closes #4302 Closes #4798 Closes #5081 - • Fix false negative for **undefined-variable** and related variable messages when the same undefined variable is used as a type annotation and is accessed multiple times, or is used as a default argument to a function. Closes #5399 - • Emit **used-before-assignment** instead of **undefined-variable** when attempting to access unused type annotations. Closes #5713 - • Fixed an issue where **ungrouped-imports** could not be disabled without raising **useless-suppression**. Refs #2366 - • Fixed a crash on **\_\_init\_\_** nodes when the attribute was previously uninferable due to a cache limit size. This limit can be hit when the inheritance pattern of a class (and therefore of the **\_\_init\_\_** attribute) is very large. Closes #5679 - • Fixed extremely long processing of long lines with comma's. Closes #5483 - • Fix false positive **super-init-not-called** for classes that inherit their **init** from a parent. Closes #4941 - • Fix false positives for **used-before-assignment** from using named expressions in a ternary operator test and using that expression as a call argument. Closes #5177, #5212 - • Fixed crash with recursion error for inference of class attributes that referenced the class itself. Closes #5408 Refs pylint-dev/astroid#1392 - • Fixed false positive for **unused-argument** when a method overridden in a subclass does nothing with the value of a keyword-only argument. Closes #5771 Refs pylint-dev/astroid#1382 - • Optimize parsing of long lines when **missing-final-newline** is enabled. Closes #5724 - • Fix false positive for **used-before-assignment** from a class definition nested under a function subclassing a class defined outside the function. Closes #4590 - • Fix **unnecessary\_dict\_index\_lookup** false positive when deleting a dictionary's entry. Closes #4716 - • Fix false positive for **used-before-assignment** when an except handler shares a name with a test in a filtered comprehension. Closes #5817 - • Fix a crash in **unused-private-member** checker when analyzing code using **type(self)** in bound methods. Closes #5569 - • Fix crash in **unnecessary-dict-index-lookup** checker if the output of **items()** is assigned to a 1-tuple. Closes #5504 - • Fixed crash with slots assignments and annotated assignments. Closes #5479 - • Fixed a crash in **unspecified-encoding** checker when providing **None** to the **mode** argument of an **open()** call. Closes #5731 - • Fixed a crash involving a **NewType** named with an f-string. Closes #5770 Refs pylint-dev/astroid#1400 - • Improved **bad-open-mode** message when providing **None** to the **mode** argument of an **open()** call. Closes #5733 - • Fix false negative for **consider-iterating-dictionary** during membership checks encapsulated in iterables or **not in** checks Closes #5323 - • Allow disabling **duplicate-code** with a disable comment when running through pylint. Closes #214 - • Fix false positive for **undefined-variable** when **namedtuple** class attributes are used as return annotations. Closes #5568 - • Added confidence level **CONTROL\_FLOW** for warnings relying on assumptions about control flow. - • **used-before-assignment** now considers that assignments in a try block may not have occurred when the except or finally blocks are executed. Closes #85, #2615 - • Fixed false negative for **used-before-assignment** when a conditional or context manager intervened before the try statement that suggested it might fail. Closes #4045 - • Fixed false negative for **used-before-assignment** in finally blocks if an except handler did not define the assignment that might have failed in the try block. - • Fix a false positive for **assigning-non-slot** when the slotted class defined **\_\_setattr\_\_**. Closes #3793 - • Fixed a false positive for **invalid-class-object** when the object being assigned to the **\_\_class\_\_** attribute is uninferable. - • Added a **testutil** extra require to the packaging, as **gitpython** should not be a dependency all the time but is still required to use the primer helper code in **pylint.testutil**. You can install it with **pip install pylint\[testutil\]**. Closes #5486 - • Fixed a false positive for **used-before-assignment** when a named expression appears as the first value in a container. Closes #5112 - • Fixed false positive for **used-before-assignment** with self-referential type annotation in conditional statements within class methods. Closes #5499 - • **used-before-assignment** now assumes that assignments in except blocks may not have occurred and warns accordingly. Closes #4761 - • When evaluating statements after an except block, **used-before-assignment** assumes that assignments in the except blocks took place if the corresponding try block contained a return statement. Closes #5500 - • Fixed a false negative for **used-before-assignment** when some but not all except handlers defined a name relied upon after an except block when the corresponding try block contained a return statement. Closes #5524 - • When evaluating statements in the **else** clause of a loop, **used-before-assignment** assumes that assignments in the except blocks took place if the except handlers constituted the only ways for the loop to finish without breaking early. Closes #5683 - • **used-before-assignment** now checks names in try blocks. - • Fixed false positive with **used-before-assignment** for assignment expressions in lambda statements. Closes #5360, #3877 - • Improve **invalid-name** check for **TypeVar** names. The accepted pattern can be customized with **--typevar-rgx**. Closes #3401 - • Fixed a false positive (affecting unreleased development) for **used-before-assignment** involving homonyms between filtered comprehensions and assignments in except blocks. Closes #5586 - • Fixed crash on list comprehensions that used **type** as inner variable name. Closes #5461 - • Fixed crash in **use-maxsplit-arg** checker when providing the **sep** argument to **str.split()** by keyword. Closes #5737 - • Fix false positive for **unused-variable** for a comprehension variable matching an outer scope type annotation. Closes #5326 - • Fix false negative for **undefined-variable** for a variable used multiple times in a comprehension matching an unused outer scope type annotation. Closes #5654 - • Require Python **3.6.2** to run pylint. Closes #5065 - • Fixed crash on uninferable decorators on Python 3.6 and 3.7 - • Emit **redefined-outer-name** when a nested except handler shadows an outer one. Closes #4434 Closes #5370 - • **encoding** can now be supplied as a positional argument to calls that open files without triggering **unspecified-encoding**. Closes #5638 - • Fatal errors now emit a score of 0.0 regardless of whether the linted module contained any statements Closes #5451 - • **fatal** was added to the variables permitted in score evaluation expressions. - • The default score evaluation now uses a floor of 0. Closes #2399 - • Fix **comparison-with-callable** false positive for callables that raise, such as typing constants. Closes #5557 - • When invoking **pylint**, **epylint**, **symilar** or **pyreverse** by importing them in a python file you can now pass an **argv** keyword besides patching **sys.argv**. Closes #5320 - • The **PyLinter** class will now be initialized with a **TextReporter** as its reporter if none is provided. - • Fix false positive **not-callable** with attributes that alias **NamedTuple** Fixes part of #1730 - • The **testutils** for unittests now accept **end\_lineno** and **end\_column**. Tests without these will trigger a **DeprecationWarning**. - • **arguments-differ** will no longer complain about method redefinitions with extra parameters that have default values. Closes #1556, #5338 - • Disables for **deprecated-module** and similar warnings for stdlib features deprecated in newer versions of Python no longer raise **useless-suppression** when linting with older Python interpreters where those features are not yet deprecated. - • Importing the deprecated stdlib module **xml.etree.cElementTree** now emits **deprecated\_module**. Closes #5862 - • Importing the deprecated stdlib module **distutils** now emits **deprecated\_module** on Python 3.10+. - • Fixed false positive **unexpected-keyword-arg** for decorators. Closes #258 - • **missing-raises-doc** will now check the class hierarchy of the raised exceptions ``` def my_function(): """My function. Raises: Exception: if something fails """ raise ValueError ``` Closes #4955 - • Fixed false positive for **unused-variable** when a **nonlocal** name is assigned as part of a multi-name assignment. Closes #3781 - • Fix false positive - Allow unpacking of **self** in a subclass of **typing.NamedTuple**. Closes #5312 - • Fixed false negative **unpacking-non-sequence** when value is an empty list. Closes #5707 - • Fixed false positive for **global-variable-not-assigned** when the **del** statement is used Closes #5333 - • Fix type hints in class diagrams generated by pyreverse for class methods and methods returning None. - • Output better error message if unsupported file formats are used with **pyreverse**. Closes #5950 - • Fixed false positive for **unused-argument** when a **nonlocal** name is used in a nested function that is returned without being called by its parent. Closes #5187 - • Avoid emitting **raising-bad-type** when there is inference ambiguity on the variable being raised. Closes #2793 - • Fix false positive for **superfluous-parens** for patterns like "return (a or b) in iterable". Closes #5803 - • Fix a crash in the **unsupported-membership-test** checker when assigning multiple constants to class attributes including **\_\_iter\_\_** via unpacking. Closes #6366 - • Fix false positive for **used-before-assignment** for assignments taking place via nonlocal declarations after an earlier type annotation. Closes #5394 - • Fixed a false positive for **unused-variable** when a builtin specified in **--additional-builtins** is given a type annotation. Closes #6388 - • Fix false positive for nonexistent-operator / E0107 \<#nonexistent-operator\>' when repeated '-' are separated (e.g. by parens). Closes #5769 - • Fix a false positive for **undefined-loop-variable** when the **else** of a **for** loop raises or returns. Closes #5971 - • Only raise **not-callable** when all the inferred values of a property are not callable. Closes #5931 - • Fix false positive for **unused-variable** for classes inside functions and where a metaclass is provided via a call. Closes #4020 - • Avoid reporting **superfluous-parens** on expressions using the **is not** operator. Closes #5930 - • Fix a false positive for **undefined-loop-variable** for a variable used in a lambda inside the first of multiple loops. Closes #6419 - • Fix false positive for **unsubscriptable-object** in Python 3.8 and below for statements guarded by **if TYPE\_CHECKING**. Closes #3979 - • Fix a crash when accessing **\_\_code\_\_** and assigning it to a variable. Closes #6539 - • Fix a crash when linting a file that passes an integer **mode=** to **open** Closes #6414 - • Fix false positives for **no-name-in-module** and **import-error** for **numpy.distutils** and **pydantic**. Closes #6497 - • Fix **IndexError** crash in **uninferable\_final\_decorators** method. Refs #6531 - • Fix a crash in **unnecessary-dict-index-lookup** when subscripting an attribute. Closes #6557 - • Fix a false positive for **undefined-loop-variable** when using **enumerate()**. Closes #6593 ### Full changelog ### What's New in Pylint 2.13.9? Release date: 2022-05-13 - • Respect ignore configuration options with **--recursive=y**. Closes #6471 - • Fix false positives for **no-name-in-module** and **import-error** for **numpy.distutils** and **pydantic**. Closes #6497 - • Fix **IndexError** crash in **uninferable\_final\_decorators** method. Refs #6531 - • Fix a crash in **unnecessary-dict-index-lookup** when subscripting an attribute. Closes #6557 - • Fix a crash when accessing **\_\_code\_\_** and assigning it to a variable. Closes #6539 - • Fix a false positive for **undefined-loop-variable** when using **enumerate()**. Closes #6593 ### What's New in Pylint 2.13.8? Release date: 2022-05-02 - • Fix a false positive for **undefined-loop-variable** for a variable used in a lambda inside the first of multiple loops. Closes #6419 - • Fix a crash when linting a file that passes an integer **mode=** to **open** Closes #6414 - • Avoid reporting **superfluous-parens** on expressions using the **is not** operator. Closes #5930 - • Fix a false positive for **undefined-loop-variable** when the **else** of a **for** loop raises or returns. Closes #5971 - • Fix false positive for **unused-variable** for classes inside functions and where a metaclass is provided via a call. Closes #4020 - • Fix false positive for **unsubscriptable-object** in Python 3.8 and below for statements guarded by **if TYPE\_CHECKING**. Closes #3979 ### What's New in Pylint 2.13.7? Release date: 2022-04-20 - • Fix a crash caused by using the new config from 2.14.0 in 2.13.x code. Closes #6408 ### What's New in Pylint 2.13.6? Release date: 2022-04-20 - • Fix a crash in the **unsupported-membership-test** checker when assigning multiple constants to class attributes including **\_\_iter\_\_** via unpacking. Closes #6366 - • Asterisks are no longer required in Sphinx and Google style parameter documentation for **missing-param-doc** and are parsed correctly. Closes #5815 Closes #5406 - • Fixed a false positive for **unused-variable** when a builtin specified in **--additional-builtins** is given a type annotation. Closes #6388 - • Fixed an **AstroidError** in 2.13.0 raised by the **duplicate-code** checker with **ignore-imports** or **ignore-signatures** enabled. Closes #6301 ### What's New in Pylint 2.13.5? Release date: 2022-04-06 - • Fix false positive regression in 2.13.0 for **used-before-assignment** for homonyms between variable assignments in try/except blocks and variables in subscripts in comprehensions. Closes #6069 Closes #6136 - • **lru-cache-decorating-method** has been renamed to **cache-max-size-none** and will only be emitted when **maxsize** is **None**. Closes #6180 - • Fix false positive for **unused-import** when disabling both **used-before-assignment** and **undefined-variable**. Closes #6089 - • Narrow the scope of the **unnecessary-ellipsis** checker to: \* functions & classes which contain both a docstring and an ellipsis. \* A body which contains an ellipsis **nodes.Expr** node & at least one other statement. - • Fix false positive for **used-before-assignment** for assignments taking place via nonlocal declarations after an earlier type annotation. Closes #5394 - • Fix crash for **redefined-slots-in-subclass** when the type of the slot is not a const or a string. Closes #6100 - • Only raise **not-callable** when all the inferred values of a property are not callable. Closes #5931 - • Fix a false negative for **subclassed-final-class** when a set of other messages were disabled. ### What's New in Pylint 2.13.4? Release date: 2022-03-31 - • Fix false positive regression in 2.13.0 for **used-before-assignment** for homonyms between variable assignments in try/except blocks and variables in a comprehension's filter. Closes #6035 - • Include **testing\_pylintrc** in source and wheel distributions. Closes #6028 - • Fix crash in **super-init-not-called** checker when using **ctypes.Union**. Closes #6027 - • Fix crash for **unnecessary-ellipsis** checker when an ellipsis is used inside of a container or a lambda expression. Closes #6036 Closes #6037 Closes #6048 ### What's New in Pylint 2.13.3? Release date: 2022-03-29 - • Fix false positive for **unnecessary-ellipsis** when using an ellipsis as a default argument. Closes #5973 - • Fix crash involving unbalanced tuple unpacking. Closes #5998 - • Fix false positive for nonexistent-operator / E0107 \<#nonexistent-operator\>' when repeated '-' are separated (e.g. by parens). Closes #5769 ### What's New in Pylint 2.13.2? Release date: 2022-03-27 - • Fix crash when subclassing a **namedtuple**. Closes #5982 - • Fix false positive for **superfluous-parens** for patterns like "return (a or b) in iterable". Closes #5803 - • Fix a false negative regression in 2.13.0 where **protected-access** was not raised on functions. Closes #5989 - • Better error messages in case of crash if pylint can't write the issue template. Refs #5987 ### What's New in Pylint 2.13.1? Release date: 2022-03-26 - • Fix a regression in 2.13.0 where **used-before-assignment** was emitted for the usage of a nonlocal in a try block. Closes #5965 - • Avoid emitting **raising-bad-type** when there is inference ambiguity on the variable being raised. Closes #2793 - • Loosen TypeVar default name pattern a bit to allow names with multiple uppercase characters. E.g. **HVACModeT** or **IPAddressT**. Closes #5981 - • Fixed false positive for **unused-argument** when a **nonlocal** name is used in a nested function that is returned without being called by its parent. Closes #5187 - • Fix program crash for **modified\_iterating-list/set/dict** when the list/dict/set being iterated through is a function call. Closes #5969 - • Don't emit **broken-noreturn** and **broken-collections-callable** errors inside **if TYPE\_CHECKING** blocks. ### What's New in Pylint 2.13.0? Release date: 2022-03-24 - • Add missing dunder methods to **unexpected-special-method-signature** check. - • No longer emit **no-member** in for loops that reference **self** if the binary operation that started the for loop uses a **self** that is encapsulated in tuples or lists. Refs pylint-dev/astroid#1360 Closes #4826 - • Output better error message if unsupported file formats are used with **pyreverse**. Closes #5950 - • Fix pyreverse diagrams type hinting for classmethods and staticmethods. - • Fix pyreverse diagrams type hinting for methods returning None. - • Fix matching **--notes** options that end in a non-word character. Closes #5840 - • Updated the position of messages for class and function definitions to no longer cover the complete definition. Only the **def** or **class** + the name of the class/function are covered. Closes #5466 - • - **using-f-string-in-unsupported-version and using-final-decorator-in-unsupported-version msgids** were renamed from **W1601** and **W1602** to **W2601** and **W2602**. Disabling using these msgids will break. This is done in order to restore consistency with the already existing msgids for **apply-builtin** and **basestring-builtin** from the now deleted python 3K+ checker. There is now a check that we're not using existing msgids or symbols from deleted checkers. Closes #5729 - • The line numbering for messages related to function arguments is now more accurate. This can require some message disables to be relocated to updated positions. - • Add **--recursive** option to allow recursive discovery of all modules and packages in subtree. Running pylint with **--recursive=y** option will check all discovered **.py** files and packages found inside subtree of directory provided as parameter to pylint. Closes #352 - • Add **modified-iterating-list**, **modified-iterating-dict** and **modified-iterating-set**, emitted when items are added to or removed from respectively a list, dictionary or set being iterated through. Closes #5348 - • Fix false-negative for **assignment-from-none** checker using list.sort() method. Closes #5722 - • New extension **import-private-name**: indicate imports of external private packages and objects (prefixed with **\_**). It can be loaded using **load-plugins=pylint.extensions.private\_import**. Closes #5463 - • Fixed crash from **arguments-differ** and **arguments-renamed** when methods were defined outside the top level of a class. Closes #5648 - • Removed the deprecated **check\_docs** extension. You can use the **docparams** checker to get the checks previously included in **check\_docs**. Closes #5322 - • Added a **testutil** extra require to the packaging, as **gitpython** should not be a dependency all the time but is still required to use the primer helper code in **pylint.testutil**. You can install it with **pip install pylint\[testutil\]**. Closes #5486 - • Reinstated checks from the python3 checker that are still useful for python 3 (**eq-without-hash**). This is now in the **pylint.extensions.eq\_without\_hash** optional extension. Closes #5025 - • Fixed an issue where **ungrouped-imports** could not be disabled without raising **useless-suppression**. Refs #2366 - • Added several checkers to deal with unicode security issues (see Trojan Sources \ and PEP 672 \ for details) that also concern the readability of the code. In detail the following checks were added: - • **bad-file-encoding** checks that the file is encoded in UTF-8 as suggested by PEP8 \. UTF-16 and UTF-32 are not supported by Python \ at the moment. If this ever changes **invalid-unicode-codec** checks that they aren't used, to allow for backwards compatibility. - • **bidirectional-unicode** checks for bidirectional unicode characters that could make code execution different than what the user expects. - • **invalid-character-backspace**, **invalid-character-carriage-return**, **invalid-character-sub**, **invalid-character-esc**, **invalid-character-zero-width-space** and **invalid-character-nul** to check for possibly harmful unescaped characters. Closes #5281 - • Use the **tomli** package instead of **toml** to parse **.toml** files. Closes #5885 - • Fix false positive - Allow unpacking of **self** in a subclass of **typing.NamedTuple**. Closes #5312 - • Fixed false negative **unpacking-non-sequence** when value is an empty list. Closes #5707 - • Better warning messages for useless else or elif when a function returns early. Closes #5614 - • Fixed false positive **consider-using-dict-comprehension** when creating a dict using a list of tuples where key AND value vary depending on the same condition. Closes #5588 - • Fixed false positive for **global-variable-undefined** when **global** is used with a class name Closes #3088 - • Fixed false positive for **unused-variable** when a **nonlocal** name is assigned as part of a multi-name assignment. Closes #3781 - • Fixed a crash in **unspecified-encoding** checker when providing **None** to the **mode** argument of an **open()** call. Closes #5731 - • Fixed a crash involving a **NewType** named with an f-string. Closes #5770 Ref pylint-dev/astroid#1400 - • Improved **bad-open-mode** message when providing **None** to the **mode** argument of an **open()** call. Closes #5733 - • Added **lru-cache-decorating-method** checker with checks for the use of **functools.lru\_cache** on class methods. This is unrecommended as it creates memory leaks by never letting the instance getting garbage collected. Closes #5670 - • Fixed crash with recursion error for inference of class attributes that referenced the class itself. Closes #5408 Ref pylint-dev/astroid#1392 - • Fixed false positive for **unused-argument** when a method overridden in a subclass does nothing with the value of a keyword-only argument. Closes #5771 Ref pylint-dev/astroid#1382 - • The issue template for crashes is now created for crashes which were previously not covered by this mechanism. Closes #5668 - • - **Rewrote checker for non-ascii-name.** It now ensures \_\_all\_\_ Python names are ASCII and also properly checks the names of imports (**non-ascii-module-import**) as well as file names (**non-ascii-file-name**) and emits their respective new warnings. Non ASCII characters could be homoglyphs (look alike characters) and hard to enter on a non specialized keyboard. See Confusable Characters in PEP 672 \ - • When run in parallel mode **pylint** now pickles the data passed to subprocesses with the **dill** package. The **dill** package has therefore been added as a dependency. - • An astroid issue where symlinks were not being taken into account was fixed Closes #1470 Closes #3499 Closes #4302 Closes #4798 Closes #5081 - • Fix a crash in **unused-private-member** checker when analyzing code using **type(self)** in bound methods. Closes #5569 - • Optimize parsing of long lines when **missing-final-newline** is enabled. Closes #5724 - • Fix false positives for **used-before-assignment** from using named expressions in a ternary operator test and using that expression as a call argument. Closes #5177, #5212 - • Fix false positive for **undefined-variable** when **namedtuple** class attributes are used as return annotations. Closes #5568 - • Fix false negative for **undefined-variable** and related variable messages when the same undefined variable is used as a type annotation and is accessed multiple times, or is used as a default argument to a function. Closes #5399 - • Pyreverse - add output in mermaidjs format - • Emit **used-before-assignment** instead of **undefined-variable** when attempting to access unused type annotations. Closes #5713 - • Added confidence level **CONTROL\_FLOW** for warnings relying on assumptions about control flow. - • **used-before-assignment** now considers that assignments in a try block may not have occurred when the except or finally blocks are executed. Closes #85, #2615 - • Fixed false negative for **used-before-assignment** when a conditional or context manager intervened before the try statement that suggested it might fail. Closes #4045 - • Fixed false negative for **used-before-assignment** in finally blocks if an except handler did not define the assignment that might have failed in the try block. - • Fixed extremely long processing of long lines with comma's. Closes #5483 - • Fixed crash on properties and inherited class methods when comparing them for equality against an empty dict. Closes #5646 - • Fixed a false positive for **assigning-non-slot** when the slotted class defined **\_\_setattr\_\_**. Closes #3793 - • Fixed a false positive for **invalid-class-object** when the object being assigned to the **\_\_class\_\_** attribute is uninferable. - • Fixed false positive for **used-before-assignment** with self-referential type annotation in conditional statements within class methods. Closes #5499 - • Add checker **redefined-slots-in-subclass**: Emitted when a slot is redefined in a subclass. Closes #5617 - • Fixed false positive for **global-variable-not-assigned** when the **del** statement is used Closes #5333 - • By default, pylint does no longer take files starting with **.#** into account. Those are considered **Emacs file locks**. See \. This behavior can be reverted by redefining the **ignore-patterns** option. Closes #367 - • Fixed a false positive for **used-before-assignment** when a named expression appears as the first value in a container. Closes #5112 - • **used-before-assignment** now assumes that assignments in except blocks may not have occurred and warns accordingly. Closes #4761 - • When evaluating statements after an except block, **used-before-assignment** assumes that assignments in the except blocks took place if the corresponding try block contained a return statement. Closes #5500 - • Fixed a false negative for **used-before-assignment** when some but not all except handlers defined a name relied upon after an except block when the corresponding try block contained a return statement. Closes #5524 - • When evaluating statements in the **else** clause of a loop, **used-before-assignment** assumes that assignments in the except blocks took place if the except handlers constituted the only ways for the loop to finish without breaking early. Closes #5683 - • **used-before-assignment** now checks names in try blocks. - • Fixed false positive with **used-before-assignment** for assignment expressions in lambda statements. Closes #5360, #3877 - • Fixed a false positive (affecting unreleased development) for **used-before-assignment** involving homonyms between filtered comprehensions and assignments in except blocks. Closes #5586 - • Fixed crash with slots assignments and annotated assignments. Closes #5479 - • Fixed crash on list comprehensions that used **type** as inner variable name. Closes #5461 - • Fixed crash in **use-maxsplit-arg** checker when providing the **sep** argument to **str.split()** by keyword. Closes #5737 - • Fix false positive for **unused-variable** for a comprehension variable matching an outer scope type annotation. Closes #5326 - • Fix false negative for **undefined-variable** for a variable used multiple times in a comprehension matching an unused outer scope type annotation. Closes #5654 - • Some files in **pylint.testutils** were deprecated. In the future imports should be done from the **pylint.testutils.functional** namespace directly. - • Fixed false positives for **no-value-for-parameter** with variadic positional arguments. Closes #5416 - • **safe\_infer** no longer makes an inference when given two function definitions with differing numbers of arguments. Closes #3675 - • Fix **comparison-with-callable** false positive for callables that raise, such as typing constants. Closes #5557 - • Fixed a crash on **\_\_init\_\_** nodes when the attribute was previously uninferable due to a cache limit size. This limit can be hit when the inheritance pattern of a class (and therefore of the **\_\_init\_\_** attribute) is very large. Closes #5679 - • Fix false positive for **used-before-assignment** from a class definition nested under a function subclassing a class defined outside the function. Closes #4590 - • Fix **unnecessary\_dict\_index\_lookup** false positive when deleting a dictionary's entry. Closes #4716 - • Fix false positive for **used-before-assignment** when an except handler shares a name with a test in a filtered comprehension. Closes #5817 - • Fix crash in **unnecessary-dict-index-lookup** checker if the output of **items()** is assigned to a 1-tuple. Closes #5504 - • When invoking **pylint**, **epylint**, **symilar** or **pyreverse** by importing them in a python file you can now pass an **argv** keyword besides patching **sys.argv**. Closes #5320 - • The **PyLinter** class will now be initialized with a **TextReporter** as its reporter if none is provided. - • Fix **super-init-not-called** when parent or **self** is a **Protocol** Closes #4790 - • Fix false positive **not-callable** with attributes that alias **NamedTuple** Fixes part of #1730 - • Emit **redefined-outer-name** when a nested except handler shadows an outer one. Closes #4434 Closes #5370 - • Fix false positive **super-init-not-called** for classes that inherit their **init** from a parent. Closes #4941 - • **encoding** can now be supplied as a positional argument to calls that open files without triggering **unspecified-encoding**. Closes #5638 - • Fatal errors now emit a score of 0.0 regardless of whether the linted module contained any statements Closes #5451 - • **fatal** was added to the variables permitted in score evaluation expressions. - • The default score evaluation now uses a floor of 0. Closes #2399 - • Fix false negative for **consider-iterating-dictionary** during membership checks encapsulated in iterables or **not in** checks Closes #5323 - • Fixed crash on uninferable decorators on Python 3.6 and 3.7 - • Add checker **unnecessary-ellipsis**: Emitted when the ellipsis constant is used unnecessarily. Closes #5460 - • Disable checker **bad-docstring-quotes** for Python \<= 3.7, because in these versions the line numbers for decorated functions and classes are not reliable which interferes with the checker. Closes #3077 - • Fixed incorrect classification of Numpy-style docstring as Google-style docstring for docstrings with property setter documentation. Docstring classification is now based on the highest amount of matched sections instead of the order in which the docstring styles were tried. - • Fixed detection of **arguments-differ** when superclass static methods lacked a **@staticmethod** decorator. Closes #5371 - • **TypingChecker** - • Added new check **broken-noreturn** to detect broken uses of **typing.NoReturn** if **py-version** is set to Python **3.7.1** or below. \ - • Added new check **broken-collections-callable** to detect broken uses of **collections.abc.Callable** if **py-version** is set to Python **3.9.1** or below. \ - • The **testutils** for unittests now accept **end\_lineno** and **end\_column**. Tests without these will trigger a **DeprecationWarning**. - • **arguments-differ** will no longer complain about method redefinitions with extra parameters that have default values. Closes #1556, #5338 - • Fixed false positive **unexpected-keyword-arg** for decorators. Closes #258 - • Importing the deprecated stdlib module **xml.etree.cElementTree** now emits **deprecated\_module**. Closes #5862 - • Disables for **deprecated-module** and similar warnings for stdlib features deprecated in newer versions of Python no longer raise **useless-suppression** when linting with older Python interpreters where those features are not yet deprecated. - • Importing the deprecated stdlib module **distutils** now emits **deprecated\_module** on Python 3.10+. - • **missing-raises-doc** will now check the class hierarchy of the raised exceptions ``` def my_function(): """My function. Raises: Exception: if something fails """ raise ValueError ``` Closes #4955 - • Disable spellchecking of mypy rule names in ignore directives. Closes #5929 - • Allow disabling **duplicate-code** with a disable comment when running through pylint. Closes #214 - • Improve **invalid-name** check for **TypeVar** names. The accepted pattern can be customized with **--typevar-rgx**. Closes #3401 - • Added new checker **typevar-name-missing-variance**. Emitted when a covariant or contravariant **TypeVar** does not end with **\_co** or **\_contra** respectively or when a **TypeVar** is not either but has a suffix. - • Allow usage of mccabe 0.7.x release Closes #5878 - • Fix **unused-private-member** false positive when accessing private methods through **property**. Closes #4756 ### What's New in Pylint 2.12 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights In 2.12, we introduced a new option **py-version** that permits to analyse code for a python version that may differ from your current python interpreter. This does not affect all checkers but permits, for example, to check for python 3.5 code smells (using f-string's) while using pylint with python 3.6. The minimum version to run pylint is now 3.6.2, while the last working version for python 3.6.0 and 3.6.1 was pylint 2.9.3. On top of fixing a lot of false positives and bugs, we also added new default checks, like **use-implicit-booleaness-not-comparison**, **overridden-final-method**, and **useless-with-lock**. There's also better check for TOML configurations. Lastly, in addition to the information we already had about start line and start column, we introduced new information about the end line and end column of messages. This will permit to have more precise visual clue in IDE like in pylint for vs-code. The default will stay the same to not break compatibility but it can be retrieved by adding **end\_line** and **end\_column** to the **--msg-template** option. For better result stick to python 3.8+. The checker for Yoda conditions is now an extension, you might want to enable it if you were relying on this check. There's also a new extension checker, **consider-using-any-or-all** that detects for loops that could be replaced by any or all, entirely contributed by @areveny, welcome to the team ! ### New checkers - • Added **missing-any-param-doc** triggered when a function has neither parameter nor parameter type documentation. Undocumented parameters are now being properly identified. A warning might start to appear unexpectedly if **missing-param-doc** and **missing-type-doc** were disabled, as a new message **missing-any-param-doc** will be emitted instead. Closes #3799 ### typing.final - • Added **overridden-final-method**: Emitted when a method which is annotated with **typing.final** is overridden - • Added **subclassed-final-class**: Emitted when a class which is annotated with **typing.final** is subclassed Closes #3197 - • Created new **UnsupportedVersionChecker** checker class that includes checks for features not supported by all versions indicated by a **py-version**. - • Added **using-f-string-in-unsupported-version** checker. Issued when **py-version** is set to a version that does not support f-strings (\< 3.6) - • Added new checker **use-implicit-booleaness-not-comparison**: Emitted when collection literal comparison is being used to check for emptiness. Closes #4774 - • Added **using-final-decorator-in-unsupported-version** checker. Issued when **py-version** is set to a version that does not support typing.final (\< 3.8) - • Added new checker **useless-with-lock** to find incorrect usage of with statement and threading module locks. Emitted when **with threading.Lock():** is used instead of **with lock\_instance:**. Closes #5208 - • A new **bad-configuration-section** checker was added that will emit for misplaced option in pylint's top level namespace for toml configuration. Top-level dictionaries or option defined in the wrong section will still silently not be taken into account, which is tracked in a follow-up issue. Follow-up in #5259 - • **MessageTest** of the unittest **testutil** now requires the **confidence** attribute to match the expected value. If none is provided it is set to **UNDEFINED**. - • **add\_message** of the unittest **testutil** now actually handles the **col\_offset** parameter and allows it to be checked against actual output in a test. ### Extensions - • Added an optional extension **consider-using-any-or-all**: Emitted when a **for** loop only produces a boolean and could be replaced by **any** or **all** using a generator. Also suggests a suitable any/all statement if it is concise. Closes #5008 - • Moved **misplaced-comparison-constant** to its own extension **comparison\_placement**. This checker was opinionated and now no longer a default. It can be reactived by adding **pylint.extensions.comparison\_placement** to **load-plugins** in your config. Closes #1064 ### Other Changes - • Fix **install graphiz** message which isn't needed for puml output format. - • **pylint** no longer crashes when checking assignment expressions within if-statements Closes #5178 - • Added configuration option **exclude-too-few-public-methods** to allow excluding classes from the **min-public-methods** checker. Closes #3370 - • Fix **accept-no-yields-doc** and **accept-no-return-doc** not allowing missing **yield** or **return** documentation when a docstring is partially correct Closes #5223 - • Fix **simplify-boolean-expression** when condition can be inferred as False. Closes #5200 - • Fix exception when pyreverse parses **property function** of a class. - • Improve and flatten **unused-wildcard-import** message Closes #3859 - • In length checker, **len-as-condition** has been renamed as **use-implicit-booleaness-not-len** in order to be consistent with **use-implicit-booleaness-not-comparison**. - • Fixed **protected-access** for accessing of attributes and methods of inner classes Closes #3066 - • Update **literal-comparison\`** checker to ignore tuple literals Closes #3031 - • The functional **testutils** now accept **end\_lineno** and **end\_column**. Expected output files without these will trigger a **DeprecationWarning**. Expected output files can be easily updated with the **python tests/test\_functional.py --update-functional-output** command. - • The functional **testutils** now correctly check the distinction between **HIGH** and **UNDEFINED** confidence. Expected output files without defined **confidence** levels will now trigger a **DeprecationWarning**. Expected output files can be easily updated with the **python tests/test\_functional.py --update-functional-output** command. - • The functional test runner now supports the option **min\_pyver\_end\_position** to control on which python versions the **end\_lineno** and **end\_column** attributes should be checked. The default value is 3.8. - • **undefined-variable** now correctly flags variables which only receive a type annotations and never get assigned a value Closes #5140 - • **undefined-variable** now correctly considers the line numbering and order of classes used in metaclass declarations Closes #4031 - • **used-before-assignment** now correctly considers references to classes as type annotation or default values in first-level methods Closes #3771 - • **undefined-variable** and **unused-variable** now correctly trigger for assignment expressions in functions defaults Refs #3688 - • **self-cls-assignment** now also considers tuple assignment - • **undefined-variable** now correctly triggers for assignment expressions in if ... else statements This includes a basic form of control flow inference for if ... else statements using constant boolean values Closes #3688 - • Fix crash for **unused-private-member** when checking private members on **\_\_class\_\_** Closes #5261 - • Fix double emitting of **not-callable** on inferable **properties** Closes #4426 - • Support configuring mixin class pattern via **mixin-class-rgx** - • Normalize the input to the **ignore-paths** option to allow both Posix and Windows paths Closes #5194 - • **missing-param-doc** now correctly parses asterisks for variable length and keyword parameters Closes #3733 - • **missing-param-doc** now correctly handles Numpy parameter documentation without explicit typing Closes #5222 - • The **--jobs** parameter now falls back to 1 if the host operating system does not have functioning shared semaphore implementation. Closes #5216 - • Crashes when a list is encountered in a toml configuration do not happen anymore. Closes #4580 - • Fix crash for **protected-access** on (outer) class traversal - • Fix **useless-super-delegation** false positive when default keyword argument is a variable. - • Make yn validator case insensitive, to allow for **True** and **False** in config files. - • The last version compatible with python '3.6.0' and '3.6.1' is pylint '2.9.3'. We did not realize that when adding incompatible typing at the time, and all versions since are broken for this interpreter. 2.12.0 meta-information will permit to download pylint on those interpreters but the installation will fail and tell you to install '2.9.3' instead. pylint 2.12.1 will require python \>= 3.6.2. Closes #5171 Follow-up in #5065 - • Added the **--enable-all-extensions** command line option. It will load all available extensions which can be listed by running **--list-extensions** - • It is now recommended to do **pylint** development on **Python** 3.8 or higher. This allows using the latest **ast** parser. - • All standard jobs in the **pylint** CI now run on **Python** 3.8 by default. We still support python 3.6 and 3.7 and run tests for those interpreters. - • Fix crash on **open()** calls when the **mode** argument is not a simple string. Fixes part of #5321 - • Add ability to add **end\_line** and **end\_column** to the **--msg-template** option. With the standard **TextReporter** this will add the line and column number of the end of a node to the output of Pylint. If these numbers are unknown, they are represented by an empty string. - • Introduced primer tests and a configuration tests framework. The helper classes available in **pylint/testutil/** are still unstable and might be modified in the near future. Closes #4412 #5287 - • Add **endLine** and **endColumn** keys to output of **JSONReporter**. Closes #5380 - • Fix false negative for **consider-iterating-dictionary** during membership checks encapsulated in iterables or **not in** checks Closes #5323 ### Full changelog ### What's New in Pylint 2.12.2? Release date: 2021-11-25 - • Fixed a false positive for **unused-import** where everything was not analyzed properly inside typing guards. - • Fixed a false-positive regression for **used-before-assignment** for typed variables in the body of class methods that reference the same class Closes #5342 - • Specified that the **ignore-paths** option considers "" to represent a windows directory delimiter instead of a regular expression escape character. - • Fixed a crash with the **ignore-paths** option when invoking the option via the command line. Closes #5437 - • Fixed handling of Sphinx-style parameter docstrings with asterisks. These should be escaped with by prepending a "". Closes #5406 - • Add **endLine** and **endColumn** keys to output of **JSONReporter**. Closes #5380 - • Fixed handling of Google-style parameter specifications where descriptions are on the line following the parameter name. These were generating false positives for **missing-param-doc**. Closes #5452 - • Fix false negative for **consider-iterating-dictionary** during membership checks encapsulated in iterables or **not in** checks Closes #5323 - • **unused-import** now check all ancestors for typing guards Closes #5316 ### What's New in Pylint 2.12.1? Release date: 2021-11-25 - • Require Python **3.6.2** to run pylint. Closes #5065 ### What's New in Pylint 2.12.0? Release date: 2021-11-24 - • Upgrade astroid to 2.9.0 Closes #4982 - • Add ability to add **end\_line** and **end\_column** to the **--msg-template** option. With the standard **TextReporter** this will add the line and column number of the end of a node to the output of Pylint. If these numbers are unknown, they are represented by an empty string. - • Introduced primer tests and a configuration tests framework. The helper classes available in **pylint/testutil/** are still unstable and might be modified in the near future. Closes #4412 #5287 - • Fix **install graphiz** message which isn't needed for puml output format. - • **MessageTest** of the unittest **testutil** now requires the **confidence** attribute to match the expected value. If none is provided it is set to **UNDEFINED**. - • **add\_message** of the unittest **testutil** now actually handles the **col\_offset** parameter and allows it to be checked against actual output in a test. - • Fix a crash in the **check\_elif** extensions where an undetected if in a comprehension with an if statement within an f-string resulted in an out of range error. The checker no longer relies on counting if statements anymore and uses known if statements locations instead. It should not crash on badly parsed if statements anymore. - • Fix **simplify-boolean-expression** when condition can be inferred as False. Closes #5200 - • Fix exception when pyreverse parses **property function** of a class. - • The functional **testutils** now accept **end\_lineno** and **end\_column**. Expected output files without these will trigger a **DeprecationWarning**. Expected output files can be easily updated with the **python tests/test\_functional.py --update-functional-output** command. - • The functional **testutils** now correctly check the distinction between **HIGH** and **UNDEFINED** confidence. Expected output files without defined **confidence** levels will now trigger a **DeprecationWarning**. Expected output files can be easily updated with the **python tests/test\_functional.py --update-functional-output** command. - • The functional test runner now supports the option **min\_pyver\_end\_position** to control on which python versions the **end\_lineno** and **end\_column** attributes should be checked. The default value is 3.8. - • Fix **accept-no-yields-doc** and **accept-no-return-doc** not allowing missing **yield** or **return** documentation when a docstring is partially correct Closes #5223 - • Add an optional extension **consider-using-any-or-all** : Emitted when a **for** loop only produces a boolean and could be replaced by **any** or **all** using a generator. Also suggests a suitable any or all statement. Closes #5008 - • Properly identify parameters with no documentation and add new message called **missing-any-param-doc** Closes #3799 - • Add checkers **overridden-final-method** & **subclassed-final-class** Closes #3197 - • Fixed **protected-access** for accessing of attributes and methods of inner classes Closes #3066 - • Added support for **ModuleNotFoundError** (**import-error** and **no-name-in-module**). **ModuleNotFoundError** inherits from **ImportError** and was added in Python **3.6** - • **undefined-variable** now correctly flags variables which only receive a type annotations and never get assigned a value Closes #5140 - • **undefined-variable** now correctly considers the line numbering and order of classes used in metaclass declarations Closes #4031 - • **used-before-assignment** now correctly considers references to classes as type annotation or default values in first-level methods Closes #3771 - • **undefined-variable** and **unused-variable** now correctly trigger for assignment expressions in functions defaults Refs #3688 - • **undefined-variable** now correctly triggers for assignment expressions in if ... else statements This includes a basic form of control flow inference for if ... else statements using constant boolean values Closes #3688 - • Added the **--enable-all-extensions** command line option. It will load all available extensions which can be listed by running **--list-extensions** - • Fix bug with importing namespace packages with relative imports Closes #2967 and #5131 - • Improve and flatten **unused-wildcard-import** message Closes #3859 - • In length checker, **len-as-condition** has been renamed as **use-implicit-booleaness-not-len** in order to be consistent with **use-implicit-booleaness-not-comparison**. - • Created new **UnsupportedVersionChecker** checker class that includes checks for features not supported by all versions indicated by a **py-version**. - • Added **using-f-string-in-unsupported-version** checker. Issued when **py-version** is set to a version that does not support f-strings (\< 3.6) - • Fix **useless-super-delegation** false positive when default keyword argument is a variable. - • Properly emit **duplicate-key** when Enum members are duplicate dictionary keys Closes #5150 - • Use **py-version** setting for alternative union syntax check (PEP 604), instead of the Python interpreter version. - • Subclasses of **dict** are regarded as reversible by the **bad-reversed-sequence** checker (Python 3.8 onwards). Closes #4981 - • Support configuring mixin class pattern via **mixin-class-rgx** - • Added new checker **use-implicit-booleaness-not-comparison**: Emitted when collection literal comparison is being used to check for emptiness. Closes #4774 - • **missing-param-doc** now correctly parses asterisks for variable length and keyword parameters Closes #3733 - • **missing-param-doc** now correctly handles Numpy parameter documentation without explicit typing Closes #5222 - • **pylint** no longer crashes when checking assignment expressions within if-statements Closes #5178 - • Update **literal-comparison\`** checker to ignore tuple literals Closes #3031 - • Normalize the input to the **ignore-paths** option to allow both Posix and Windows paths Closes #5194 - • Fix double emitting of **not-callable** on inferable **properties** Closes #4426 - • **self-cls-assignment** now also considers tuple assignment - • Fix **missing-function-docstring** not being able to check **\_\_init\_\_** and other magic methods even if the **no-docstring-rgx** setting was set to do so - • Added **using-final-decorator-in-unsupported-version** checker. Issued when **py-version** is set to a version that does not support **typing.final** (\< 3.8) - • Added configuration option **exclude-too-few-public-methods** to allow excluding classes from the **min-public-methods** checker. Closes #3370 - • The **--jobs** parameter now fallbacks to 1 if the host operating system does not have functioning shared semaphore implementation. Closes #5216 - • Fix crash for **unused-private-member** when checking private members on **\_\_class\_\_** Closes #5261 - • Crashes when a list is encountered in a toml configuration do not happen anymore. Closes #4580 - • Moved **misplaced-comparison-constant** to its own extension **comparison\_placement**. This checker was opinionated and now no longer a default. It can be reactived by adding **pylint.extensions.comparison\_placement** to **load-plugins** in your config. Closes #1064 - • A new **bad-configuration-section** checker was added that will emit for misplaced option in pylint's top level namespace for toml configuration. Top-level dictionaries or option defined in the wrong section will still silently not be taken into account, which is tracked in a follow-up issue. Follow-up in #5259 - • Fix crash for **protected-access** on (outer) class traversal - • Added new checker **useless-with-lock** to find incorrect usage of with statement and threading module locks. Emitted when **with threading.Lock():** is used instead of **with lock\_instance:**. Closes #5208 - • Make yn validator case insensitive, to allow for **True** and **False** in config files. - • Fix crash on **open()** calls when the **mode** argument is not a simple string. Fixes part of #5321 - • Inheriting from a class that implements **\_\_class\_getitem\_\_** no longer raises **inherit-non-class**. - • Pyreverse - Add the project root directory to sys.path Closes #2479 - • Don't emit **consider-using-f-string** if **py-version** is set to Python \< **3.6**. **f-strings** were added in Python **3.6** Closes #5019 - • Fix regression for **unspecified-encoding** with **pathlib.Path.read\_text()** Closes #5029 - • Don't emit **consider-using-f-string** if the variables to be interpolated include a backslash - • Fixed false positive for **cell-var-from-loop** when variable is used as the default value for a keyword-only parameter. Closes #5012 - • Fix false-positive **undefined-variable** with **Lambda**, **IfExp**, and assignment expression. - • Fix false-positive **useless-suppression** for **wrong-import-order** Closes #2366 - • Fixed **toml** dependency issue Closes #5066 - • Fix false-positive **useless-suppression** for **line-too-long** Closes #4212 - • Fixed **invalid-name** not checking parameters of overwritten base **object** methods Closes #3614 - • Fixed crash in **consider-using-f-string** if **format** is not called Closes #5058 - • Fix crash with **AssignAttr** in **if TYPE\_CHECKING** blocks. Closes #5111 - • Improve node information for **invalid-name** on function argument. - • Prevent return type checkers being called on functions with ellipses as body Closes #4736 - • Add **is\_sys\_guard** and **is\_typing\_guard** helper functions from astroid to **pylint.checkers.utils**. - • Fix regression on ClassDef inference Closes #5030 Closes #5036 - • Fix regression on Compare node inference Closes #5048 - • Fix false-positive **isinstance-second-argument-not-valid-type** with **typing.Callable**. Closes #3507 Closes #5087 - • It is now recommended to do **pylint** development on **Python** 3.8 or higher. This allows using the latest **ast** parser. - • All standard jobs in the **pylint** CI now run on **Python** 3.8 by default. We still support python 3.6 and 3.7 and run tests for those interpreters. - • **TypingChecker** - • Fix false-negative for **deprecated-typing-alias** and **consider-using-alias** with **typing.Type** + **typing.Callable**. ### What's New in Pylint 2.11 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights In 2.11, we added a new default checker to advise using f-string as it's the most efficient way of formatting strings right now. You can use pyupgrade \, ruff \ or flynt \ to migrate your old **%** and **format()** automatically. We added a new extension **SetMembershipChecker** that will advise the use of set for membership test, as it's more performant than lists or tuples. The **CodeStyleChecker** also got some love, check it out if you're not already using it. We fixed some long standing bugs, false positives, or false negatives and we added small quality of life options like **min-similarity-lines** that disable the duplication check when set to 0. Under the hood the code for both pylint and astroid is progressively more typed, which could be helpful to you if you're using them as libraries. In order for this new typing to make more sense and stay simple, we deprecated some functions or type that will be removed in the next major version. This is an ongoing effort. The future **possible-forgotten-f-prefix** check still had too much false positives, and is delayed again. Check the possible-forgotten-f-prefix \ issue if you want to provide knowledge or use case :) ### New checkers - • Added **consider-using-f-string**: Emitted when .format() or '%' is being used to format a string. Closes #3592 ### Removed checkers - • The python3 porting mode checker and its **py3k** option were removed. You can still find it in older pylint versions. ### Extensions - • Added new extension **SetMembershipChecker** with **use-set-for-membership** check: Emitted when using an in-place defined **list** or **tuple** to do a membership test. **sets** are better optimized for that. Closes #4776 ### CodeStyleChecker - • Added **consider-using-assignment-expr**: Emitted when an assignment is directly followed by an if statement and both can be combined by using an assignment expression **:=**. Requires Python 3.8 Closes #4862 ### Other Changes - • Added **py-version** config key (if **\[MAIN\]** section). Used for version dependent checks. Will default to whatever Python version pylint is executed with. - • The **invalid-name** message is now more detailed when using multiple naming style regexes. - • Fix false positive for **consider-using-with** if a context manager is assigned to a variable in different paths of control flow (e. g. if-else clause). Closes #4751 - • Fix false positive for **function-redefined** for simple type annotations Closes #4936 - • Fix false positive for **protected-access** if a protected member is used in type hints of function definitions - • Fix false positive **dict-iter-missing-items** for dictionaries only using tuples as keys Closes #3282 - • The **unspecified-encoding** checker now also checks calls to **pathlib.Path().read\_text()** and **pathlib.Path().write\_text()** Closes #4945 - • Fix false positive **superfluous-parens** for tuples created with inner tuples Closes #4907 - • Fix false positive **unused-private-member** for accessing attributes in a class using **cls** Closes #4849 - • Extended **consider-using-in** check to work for attribute access. - • Setting **min-similarity-lines** to 0 now makes the similarty checker stop checking for duplicate code Closes #4901 - • Fix a bug where pylint complained if the cache's parent directory does not exist Closes #4900 - • The **global-variable-not-assigned** checker now catches global variables that are never reassigned in a local scope and catches (reassigned) functions Closes #1375 Closes #330 - • The **consider-iterating-dictionary** checker now also considers membership checks Closes #4069 ### Full changelog ### What's New in Pylint 2.11.1? Release date: 2021-09-16 - • **unspecified-encoding** now checks the encoding of **pathlib.Path()** correctly Closes #5017 ### What's New in Pylint 2.11.0? Release date: 2021-09-16 - • The python3 porting mode checker and its **py3k** option were removed. You can still find it in older pylint versions. - • **raising-bad-type** is now properly emitted when raising a string - • Added new extension **SetMembershipChecker** with **use-set-for-membership** check: Emitted when using an in-place defined **list** or **tuple** to do a membership test. **sets** are better optimized for that. Closes #4776 - • Added **py-version** config key (if **\[MASTER\]** section). Used for version dependent checks. Will default to whatever Python version pylint is executed with. - • **CodeStyleChecker**: Added **consider-using-assignment-expr**: Emitted when an assignment is directly followed by an if statement and both can be combined by using an assignment expression **:=**. Requires Python 3.8 Closes #4862 - • Added **consider-using-f-string**: Emitted when .format() or '%' is being used to format a string. Closes #3592 - • Fix false positive for **consider-using-with** if a context manager is assigned to a variable in different paths of control flow (e. g. if-else clause). Closes #4751 - • https is now preferred in the documentation and \ correctly redirect to \ Closes #3802 - • Fix false positive for **function-redefined** for simple type annotations Closes #4936 - • Fix false positive for **protected-access** if a protected member is used in type hints of function definitions - • Fix false positive **dict-iter-missing-items** for dictionaries only using tuples as keys Closes #3282 - • The **unspecified-encoding** checker now also checks calls to **pathlib.Path().read\_text()** and **pathlib.Path().write\_text()** Closes #4945 - • Fix false positive **superfluous-parens** for tuples created with inner tuples Closes #4907 - • Fix false positive **unused-private-member** for accessing attributes in a class using **cls** Closes #4849 - • Fix false positive **unused-private-member** for private staticmethods accessed in classmethods. Closes #4849 - • Extended **consider-using-in** check to work for attribute access. - • Setting **min-similarity-lines** to 0 now makes the similarty checker stop checking for duplicate code Closes #4901 - • Fix a bug where pylint complained if the cache's parent directory does not exist Closes #4900 - • The **global-variable-not-assigned** checker now catches global variables that are never reassigned in a local scope and catches (reassigned) functions Closes #1375 Closes #330 - • Fix false positives for invalid-all-format / E0605 \<#invalid-all-format\> that are lists or tuples at runtime Closes #4711 - • Fix **no-self-use** and **docparams extension** for async functions and methods. - • Add documentation for **pyreverse** and **symilar** Closes #4616 - • Non symbolic messages with the wrong capitalisation now correctly trigger **use-symbolic-message-instead** Closes #5000 - • The **consider-iterating-dictionary** checker now also considers membership checks Closes #4069 - • The **invalid-name** message is now more detailed when using multiple naming style regexes. ### What's New In Pylint 2.10 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights In 2.10, we added several new default check, like **unspecified-encoding**, **forgotten-debug-statement** or **use-dict-literal**. There's also a few opinionated optional one. You can now forbid while loop or profess your exclusive love of ternary expressions publicly. We promise you hours of arguing fun with your whole team if you add those to your configuration. We've also fixed some long standing bugs, false positives, or missing options like **ignore-signature** that will now work on inner function's signatures. A new option to disable the next line, **disable-next**, has been added. It's also possible to export colored diagrams, and plantuml diagram using pyreverse. **PYLINT\_HOME** is now **XDG\_CACHE\_HOME** if not set. The performance of the similarity checker has been improved, as well as several small performance fixes. We're going to continue working on improving performance during 2.11. We're also going to finalize a new **possible-forgotten-f-prefix** check that had too much false positives at release time. Check the possible-forgotten-f-prefix \ issue if you want to provide knowledge or use case :) ### New checkers - • Added **unspecified-encoding**: Emitted when open() is called without specifying an encoding Closes #3826 - • Added **use-list-literal**: Emitted when **list()** is called with no arguments instead of using **\[\]** Closes #4365 - • Added **use-dict-literal**: Emitted when **dict()** is called with no arguments instead of using **{}** Closes #4365 - • Added **forgotten-debug-statement**: Emitted when **breakpoint**, **pdb.set\_trace** or **sys.breakpointhook** calls are found Closes #3692 - • Added **use-sequence-for-iteration**: Emitted when iterating over an in-place defined **set**. - • Added **format-string-without-interpolation** checker: Emitted when formatting is applied to a string without any variables to be replaced Closes #4042 - • Added **redundant-u-string-prefix** checker: Emitted when the u prefix is added to a string Closes #4102 ### Extensions - • **CodeStyleChecker** - • Limit **consider-using-tuple** to be emitted only for in-place defined **lists**. - • Emit **consider-using-tuple** even if list contains a **starred** expression. - • Added optional extension **consider-ternary-expression**: Emitted whenever a variable is assigned in both branches of an if/else block. Closes # 4366 - • Added optional extension **while-used**: Emitted whenever a **while** loop is used. Closes # 4367 ### Other Changes - • pyreverse now permit to produce colored generated diagram by using the **colorized** option. - • Pyreverse - add output in PlantUML format - • **consider-using-with** is no longer triggered if a context manager is returned from a function. - • pylint does not crash with a traceback anymore when a file is problematic. It creates a template text file for opening an issue on the bug tracker instead. The linting can go on for other non problematic files instead of being impossible. - • Pyreverse - Show class has-a relationships inferred from type-hints - • Performance of the Similarity checker has been improved. - • Added **time.clock** to deprecated functions/methods for python 3.3 - • Added **ignored-parents** option to the design checker to ignore specific classes from the **too-many-ancestors** check (R0901). - • Don't emit **no-member** error if guarded behind if statement. Refs #1162 Closes #1990 Closes #4168 - • Fix false positives for **superfluous-parens** with walrus operator, ternary operator and inside list comprehension. Closes #2818 Closes #3249 Closes #3608 Closes #4346 - • Refactor of **--list-msgs** & **--list-msgs-enabled**: both options now show whether messages are emittable with the current interpreter. Closes #4778 - • Fix false negative for **used-before-assignment** when the variable is assigned in an exception handler, but used outside of the handler. Closes #626 - • Added **disable-next** option: allows using *# pylint: disable-next=msgid* to disable a message for the following line Closes #1682 - • Fixed **cell-var-from-loop** checker: handle cell variables in comprehensions within functions, and function default argument expressions. Also handle basic variable shadowing. Closes #2846 Closes #3107 - • Fixed bug with **cell-var-from-loop** checker: it no longer has false negatives when both **unused-variable** and **used-before-assignment** are disabled. - • Class methods' signatures are now ignored the same way as functions' with similarities "ignore-signatures" option enabled Closes #4653 ### Full changelog ### What's New in Pylint 2.10.2? Release date: 2021-08-21 - • We now use platformdirs instead of appdirs since the latter is not maintained. Closes #4886 - • Fix a crash in the checker raising **shallow-copy-environ** when failing to infer on **copy.copy** Closes #4891 ### What's New in Pylint 2.10.1? Release date: 2021-08-20 - • pylint does not crash when PYLINT\_HOME does not exist. Closes #4883 ### What's New in Pylint 2.10.0? Release date: 2021-08-20 - • pyreverse: add option to produce colored output. Closes #4488 - • pyreverse: add output in PlantUML format. Closes #4498 - • **consider-using-with** is no longer triggered if a context manager is returned from a function. Closes #4748 - • pylint does not crash with a traceback anymore when a file is problematic. It creates a template text file for opening an issue on the bug tracker instead. The linting can go on for other non problematic files instead of being impossible. - • pyreverse: Show class has-a relationships inferred from the type-hint Closes #4744 - • Fixed a crash when importing beyond the top level package during **import-error** message creation Closes #4775 - • Added **ignored-parents** option to the design checker to ignore specific classes from the **too-many-ancestors** check (R0901). Fixes part of #3057 - • Added **unspecified-encoding**: Emitted when open() is called without specifying an encoding Closes #3826 - • Improved the Similarity checker performance. Fix issue with **--min-similarity-lines** used with **--jobs**. Closes #4120 Closes #4118 - • Don't emit **no-member** error if guarded behind if statement. Refs #1162 Closes #1990 Closes #4168 - • The default for **PYLINTHOME** is now the standard **XDG\_CACHE\_HOME**, and pylint now uses **appdirs**. Closes #3878 - • Added **use-list-literal**: Emitted when **list()** is called with no arguments instead of using **\[\]** Closes #4365 - • Added **use-dict-literal**: Emitted when **dict()** is called with no arguments instead of using **{}** Closes #4365 - • Added optional extension **consider-ternary-expression**: Emitted whenever a variable is assigned in both branches of an if/else block. Closes # 4366 - • Added optional extension **while-used**: Emitted whenever a **while** loop is used. Closes # 4367 - • Added **forgotten-debug-statement**: Emitted when **breakpoint**, **pdb.set\_trace** or **sys.breakpointhook** calls are found Closes #3692 - • Fix false-positive of **unused-private-member** when using nested functions in a class Closes #4673 - • Fix crash for **unused-private-member** that occurred with nested attributes. Closes #4755 - • Fix a false positive for **unused-private-member** with class names Closes #4681 - • Fix false positives for **superfluous-parens** with walrus operator, ternary operator and inside list comprehension. Closes #2818 Closes #3249 Closes #3608 Closes #4346 - • Added **format-string-without-interpolation** checker: Emitted when formatting is applied to a string without any variables to be replaced Closes #4042 - • Refactor of **--list-msgs** & **--list-msgs-enabled**: both options now show whether messages are emittable with the current interpreter. Closes #4778 - • Fix false negative for **used-before-assignment** when the variable is assigned in an exception handler, but used outside of the handler. Closes #626 - • Added **disable-next** option: allows using *# pylint: disable-next=msgid* to disable a message for the following line Closes #1682 - • Added **redundant-u-string-prefix** checker: Emitted when the u prefix is added to a string Closes #4102 - • Fixed **cell-var-from-loop** checker: handle cell variables in comprehensions within functions, and function default argument expressions. Also handle basic variable shadowing. Closes #2846 Closes #3107 - • Fixed bug with **cell-var-from-loop** checker: it no longer has false negatives when both **unused-variable** and **used-before-assignment** are disabled. - • Fix false positive for **invalid-all-format** if the list or tuple builtin functions are used Closes #4711 - • Config files can now contain environment variables Closes #3839 - • Fix false-positive **used-before-assignment** with an assignment expression in a **Return** node Closes #4828 - • Added **use-sequence-for-iteration**: Emitted when iterating over an in-place defined **set**. - • **CodeStyleChecker** - • Limit **consider-using-tuple** to be emitted only for in-place defined **lists**. - • Emit **consider-using-tuple** even if list contains a **starred** expression. - • Ignore decorators lines by similarities checker when ignore signatures flag enabled Closes #4839 - • Allow **true** and **false** values in **pylintrc** for better compatibility with **toml** config. - • Class methods' signatures are ignored the same way as functions' with similarities "ignore-signatures" option enabled Closes #4653 - • Improve performance when inferring **Call** nodes, by utilizing caching. - • Improve error message for invalid-metaclass / E1139 \<#invalid-metaclass\> when the node is an Instance. ### What's New In Pylint 2.9 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights Pylint is now compatible with python 3.10. A lot of new checks have been added, some non-opinionated performance warnings like **use-maxsplit-arg**, some consensual style warnings like **unnecessary-dict-index-lookup** or new deprecation checks. We're aiming to reduce pylint noise for first time users and making some new checks optional is a step in that direction. In order to do that we created an optional code style checker that can be loaded using **pylint.extensions.code\_style** with the **load-plugins** options. More than ever, if as a veteran you want the most checks you can possibly get, you should check the list of pylint extensions. \. ### New checkers - • **deprecated-decorator**: Emitted when deprecated decorator is used. - • **consider-using-dict-items**: Emitted when iterating over dictionary keys and then indexing the same dictionary with the key within loop body. - • **use-maxsplit-arg**: Emitted either when accessing only the first or last element of **str.split()**. - • An **ignore\_signatures** option has been added to the similarity checker. It will permits to reduce false positives when multiple functions have the same parameters. - • **unnecessary-dict-index-lookup**: Emitted when iterating over dictionary items (key-value pairs) and accessing the value by index lookup. - • **consider-using-from-import**: Emitted when a submodule/member of a package is imported and aliased with the same name. - • New checker **unused-private-member**: Emitted when a private member (i.e., starts with **\_\_**) of a class is defined but not used. - • New checker **invalid-class-object**: Emitted when a non-class is assigned to a **\_\_class\_\_** attribute. - • **invalid-all-format**: Emitted when **\_\_all\_\_** has an invalid format, i.e. isn't a **tuple** or **list**. - • New checker **await-outside-async**: Emitted when await is used outside an async function. - • Add new extension **CodeStyleChecker**. It includes checkers that can improve code consistency. As such they don't necessarily provide a performance benefit and are often times opinionated. - • **consider-using-tuple**: Emitted when an in-place defined list or set can be replaced by a tuple. - • **consider-using-namedtuple-or-dataclass**: Emitted when dictionary values can be replaced by namedtuples or dataclass instances. ### Other Changes - • Fix false-positive **consider-using-with** (R1732) if a ternary conditional is used together with **with** - • Fix false-positive **consider-using-with** (R1732) if **contextlib.ExitStack** takes care of calling the **\_\_exit\_\_** method - • Add type annotations to pyreverse dot files - • Pylint's tags are now the standard form **vX.Y.Z** and not **pylint-X.Y.Z** anymore. - • Fix false-positive **too-many-ancestors** when inheriting from builtin classes, especially from the **collections.abc** module - • The output messages for **arguments-differ** error message have been customized based on the different error cases. - • New option **--fail-on=\** to return non-zero exit codes regardless of **fail-under** value. - • A new error called **arguments-renamed** has been created, which identifies any changes at the parameter names of overridden functions. It aims to separate the functionality of **arguments-differ**. - • Fix incompatibility with Python 3.6.0 caused by **typing.Counter** and **typing.NoReturn** usage - • Allow comma-separated list in **output-format** and separate output files for each specified format. Each output file can be defined after a semicolon for example : **--output-format=json:myfile.json,colorized** - • The **using-constant-test** checker now detects constant tests consisting of list literals like **\[\]** and **\[1, 2, 3\]**. - • **ignore-paths** configuration directive has been added. Defined regex patterns are matched against file path. - • Added handling of floating point values when parsing configuration from pyproject.toml - • Fix false positive **useless-type-doc** on ignored argument using **pylint.extensions.docparams** when a function was typed using pep484 but not inside the docstring. - • Fix missing support for detecting deprecated aliases to existing functions/methods. functions/methods. - • Added various deprecated functions/methods for python 3.10, 3.7, 3.6 and 3.3 - • No longer emit **consider-using-with** for **ThreadPoolExecutor** and **ProcessPoolExecutor** as they have legitimate use cases without a **with** block. - • Fix crash if a callable returning a context manager was assigned to a list or dict item ### Full changelog ### What's New in Pylint 2.9.6? Release date: 2021-07-28 - • Fix a false positive **undefined-variable** when variable name in decoration matches function argument Closes #3791 ### What's New in Pylint 2.9.5? Release date: 2021-07-21 - • Fix a crash when there would be a 'TypeError object does not support item assignment' in the code we parse. Closes #4439 - • Fix crash if a callable returning a context manager was assigned to a list or dict item Closes #4732 - • Fix a crash when an AttributeInferenceError was not handled properly when failing to infer the real name of an import in astroid. Closes #4692 ### What's New in Pylint 2.9.4? Release date: 2021-07-20 - • Added **time.clock** to deprecated functions/methods for python 3.3 - • Fix bug in which --fail-on can return a zero exit code even when the specified issue is present Closes #4296 Closes #3363 - • Fix hard failure when handling missing attribute in a class with duplicated bases Closes #4687 - • Fix false-positive **consider-using-with** (R1732) if a ternary conditional is used together with **with** Closes #4676 - • Fix false-positive **deprecated-module** when relative import uses deprecated module name. Closes #4629 - • Fix false-positive **consider-using-with** (R1732) if **contextlib.ExitStack** takes care of calling the **\_\_exit\_\_** method Closes #4654 - • Fix a false positive for **unused-private-member** when mutating a private attribute with **cls** Closes #4657 - • Fix ignored empty functions by similarities checker with "ignore-signatures" option enabled Closes #4652 - • Fix false-positive of **use-maxsplit-arg** when index is incremented in a loop Closes #4664 - • Don't emit **cyclic-import** message if import is guarded by **typing.TYPE\_CHECKING**. Closes #3525 - • Fix false-positive **not-callable** with alternative **TypedDict** syntax Closes #4715 - • Clarify documentation for consider-using-from-import / R0402 \<#consider-using-from-import\> - • Don't emit **unreachable** warning for empty generator functions Closes #4698 - • Don't emit **import-error**, **no-name-in-module**, and **ungrouped-imports** for imports guarded by **sys.version\_info** or **typing.TYPE\_CHECKING**. Closes #3285 Closes #3382 - • Fix **invalid-overridden-method** with nested property Closes #4368 - • Fix false-positive of **unused-private-member** when using **\_\_new\_\_** in a class Closes #4668 - • No longer emit **consider-using-with** for **ThreadPoolExecutor** and **ProcessPoolExecutor** as they have legitimate use cases without a **with** block. Closes #4689 - • Fix crash when inferring variables assigned in match patterns Closes #4685 - • Fix a crash when a StopIteration was raised when inferring a faulty function in a context manager. Closes #4723 ### What's New in Pylint 2.9.3? Release date: 2021-07-01 - • Fix a crash that happened when analysing empty function with docstring in the **similarity** checker. Closes #4648 - • The **similarity** checker no longer add three trailing whitespaces for empty lines in its report. ### What's New in Pylint 2.9.2? Release date: 2021-07-01 - • Fix a crash that happened when analysing code using **type(self)** to access a class attribute in the **unused-private-member** checker. Closes #4638 - • Fix a false positive for **unused-private-member** when accessing a private variable with **self** Closes #4644 - • Fix false-positive of **unnecessary-dict-index-lookup** and **consider-using-dict-items** for reassigned dict index lookups Closes #4630 ### What's New in Pylint 2.9.1? Release date: 2021-06-30 - • Upgrade astroid to 2.6.2 Closes #4631 Closes #4633 ### What's New in Pylint 2.9.0? Release date: 2021-06-29 - • Python 3.10 is now supported. - • Add type annotations to pyreverse dot files Closes #1548 - • Fix missing support for detecting deprecated aliases to existing functions/methods. Closes #4618 - • astroid has been upgraded to 2.6.1 - • Added various deprecated functions/methods for python 3.10, 3.7, 3.6 and 3.3 - • Fix false positive **useless-type-doc** on ignored argument using **pylint.extensions.docparams** when a function was typed using pep484 but not inside the docstring. Closes #4117 Closes #4593 - • **setuptools\_scm** has been removed and replaced by **tbump** in order to not have hidden runtime dependencies to setuptools - • Fix a crash when a test function is decorated with **@pytest.fixture** and astroid can't infer the name of the decorator when using **open** without **with**. Closes #4612 - • Added **deprecated-decorator**: Emitted when deprecated decorator is used. Closes #4429 - • Added **ignore-paths** behaviour. Defined regex patterns are matched against full file path. Closes #2541 - • Fix false negative for **consider-using-with** if calls like **open()** were used outside of assignment expressions. - • The warning for **arguments-differ** now signals explicitly the difference it detected by naming the argument or arguments that changed and the type of change that occurred. - • Suppress **consider-using-with** inside context managers. Closes #4430 - • Added **--fail-on** option to return non-zero exit codes regardless of **--fail-under** value. - • numversion tuple contains integers again to fix multiple pylint's plugins that relied on it Closes #4420 - • Fix false-positive **too-many-ancestors** when inheriting from builtin classes, especially from the **collections.abc** module Closes #4166 Closes #4415 - • Stdlib deprecated modules check is moved to stdlib checker. New deprecated modules are added. - • Fix raising false-positive **no-member** on abstract properties - • Created new error message called **arguments-renamed** which identifies any changes at the parameter names of overridden functions. Closes #3536 - • New checker **consider-using-dict-items**. Emitted when iterating over dictionary keys and then indexing the same dictionary with the key within loop body. Closes #3389 - • Don't emit **import-error** if import guarded behind **if sys.version\_info \>= (x, x)** - • Fix incompatibility with Python 3.6.0 caused by **typing.Counter** and **typing.NoReturn** usage Closes #4412 - • New checker **use-maxsplit-arg**. Emitted either when accessing only the first or last element of **str.split()**. Closes #4440 - • Add ignore\_signatures to duplicate code checker Closes #3619 - • Fix documentation errors in "Block disables" paragraph of User Guide. - • New checker **unnecessary-dict-index-lookup**. Emitted when iterating over dictionary items (key-value pairs) and accessing the value by index lookup. Closes #4470 - • New checker\`\`consider-using-from-import\`\`. Emitted when a submodule/member of a package is imported and aliased with the same name. Closes #2309 - • Allow comma-separated list in **output-format** and separate output files for each specified format. Closes #1798 - • Make **using-constant-test** detect constant tests consisting of list literals like **\[\]** and **\[1, 2, 3\]**. - • Improved error message of **unnecessary-comprehension** checker by providing code suggestion. Closes #4499 - • New checker **unused-private-member**. Emitted when a private member (i.e., starts with **\_\_**) of a class is defined but not used. Closes #4483 - • Fix false negative of **consider-using-enumerate** when iterating over an attribute. Closes #3657 - • New checker **invalid-class-object**. Emitted when a non-class is assigned to a **\_\_class\_\_** attribute. Closes #585 - • Fix a crash when a plugin from the configuration could not be loaded and raise an error bad-plugin-value / E0013 \<#bad-plugin-value\>' instead Closes #4555 - • Added handling of floating point values when parsing configuration from pyproject.toml Closes #4518 - • **invalid-length-returned**, now also works when nothing at all is returned following an upgrade in astroid. - • **logging-format-interpolation** and **logging-not-lazy**, now works on logger class created from renamed logging import following an upgrade in astroid. - • Fix false-positive **no-member** with generic base class Closes pylint-dev/astroid#942 - • Fix **assigning-non-slot** false-positive with base that inherits from **typing.Generic** Closes #4509 Closes pylint-dev/astroid#999 - • New checker **invalid-all-format**. Emitted when **\_\_all\_\_** has an invalid format, i.e. isn't a **tuple** or **list**. - • Fix false positive **unused-variable** and **undefined-variable** with Pattern Matching in Python 3.10 - • New checker **await-outside-async**. Emitted when await is used outside an async function. - • Clarify documentation for **typing** extension. Closes #4545 - • Add new extension **CodeStyleChecker**. It includes checkers that can improve code consistency. As such they don't necessarily provide a performance benefit and are often times opinionated. - • New checker **consider-using-tuple**. Emitted when an in-place defined list or set can be replaced by a tuple. - • New checker **consider-using-namedtuple-or-dataclass**. Emitted when dictionary values can be replaced by namedtuples or dataclass instances. - • Fix error that occurred when using **slice** as subscript for dict. - • Reduce false-positives around inference of **.value** and **.name** properties on **Enum** subclasses, following an upgrade in astroid Closes #1932 Closes #2062 - • Fix issue with **cached\_property** that caused **invalid-overridden-method** error when overriding a **property**. Closes #4023 - • Fix **unused-import** false positive for imported modules referenced in attribute lookups in type comments. Closes #4603 ### What's New In Pylint 2.8 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights ### Breaking changes - • The 'doc' extra-require has been removed. *\_\_pkginfo\_\_\`* does not contain the package metadata anymore (except **numversion**, until 3.0). Meta-information are accessible with **\`python** **from importlib import metadata** **metadata.metadata('pylint')** **\`** Prefer that to an import from **\_\_pkginfo\_\_**. ### New checkers - • New refactoring message **consider-using-with**. This message is emitted if resource-allocating functions or methods of the standard library (like **open()** or **threading.Lock.acquire()**) that can be used as a context manager are called without a **with** block. - • Add **deprecated-argument** check for deprecated arguments. - • Add new extension **ConfusingConsecutiveElifChecker**. This optional checker emits a refactoring message (R5601 **confusing-consecutive-elif**) if if/elif statements with different indentation levels follow directly one after the other. - • Add **consider-using-min-max-builtin** check for if statement which could be replaced by Python builtin min or max. - • Add new extension **TypingChecker**. This optional checker can detect the use of deprecated typing aliases and can suggest the use of the alternative union syntax where possible. (For example, 'typing.Dict' can be replaced by 'dict', and 'typing.Unions' by '\|', etc.) Make sure to check the config options if you plan on using it! - • Add **deprecated-class** check for deprecated classes. ### Other Changes - • New option **--output=\** to output result to a file rather than printing to stdout. Closes #1070 - • Reduce usage of blacklist/whitelist terminology. Notably, **extension-pkg-allow-list** is an alternative to **extension-pkg-whitelist** and the message **blacklisted-name** is now emitted as **disallowed-name**. The previous names are accepted to maintain backward compatibility. - • The packaging is now done via setuptools exclusively. **doc**, **tests**, **man**, **elisp** and **Changelog** are not packaged anymore - reducing the size of the package by 75%. - • Updated **astroid** to 2.5.4 - • COPYING has been renamed to LICENSE for standardization. ### Full changelog ### What's New in Pylint 2.8.3? Release date: 2021-05-31 - • Astroid has been pinned to 2.5.6 for the 2.8 branch. Refs #4527 ### What's New in Pylint 2.8.2? Release date: 2021-04-26 - • Keep **\_\_pkginfo\_\_.numversion** a tuple to avoid breaking pylint-django. Closes #4405 - • scm\_setuptools has been added to the packaging. - • Pylint's tags are now the standard form **vX.Y.Z** and not **pylint-X.Y.Z** anymore. - • New warning message **deprecated-class**. This message is emitted if import or call deprecated class of the standard library (like **collections.Iterable** that will be removed in Python 3.10). Closes #4388 ### What's New in Pylint 2.8.1? Release date: 2021-04-25 - • Add numversion back (temporarily) in **\_\_pkginfo\_\_** because it broke Pylama and revert the unnecessary **pylint.version** breaking change. Closes #4399 ### What's New in Pylint 2.8.0? Release date: 2021-04-24 - • New refactoring message **consider-using-with**. This message is emitted if resource-allocating functions or methods of the standard library (like **open()** or **threading.Lock.acquire()**) that can be used as a context manager are called without a **with** block. Closes #3413 - • Resolve false positives on unused variables in decorator functions Closes #4252 - • Add new extension **ConfusingConsecutiveElifChecker**. This optional checker emits a refactoring message (R5601 **confusing-consecutive-elif**) if if/elif statements with different indentation levels follow directly one after the other. - • New option **--output=\** to output result to a file rather than printing to stdout. Closes #1070 - • Use a prescriptive message for **unidiomatic-typecheck** Closes #3891 - • Apply **const-naming-style** to module constants annotated with **typing.Final** - • The packaging is now done via setuptools exclusively. **doc**, **tests**, **man**, **elisp** and **Changelog** are not packaged anymore - reducing the size of the package by 75%. - • Debian packaging is now (officially) done in \. - • The 'doc' extra-require has been removed. - • **\_\_pkginfo\_\_** now only contain **\_\_version\_\_** (also accessible with **pylint.\_\_version\_\_**), other meta-information are still accessible with **from importlib import metadata;metadata.metadata('pylint')**. - • COPYING has been renamed to LICENSE for standardization. - • Fix false-positive **used-before-assignment** in function returns. Closes #4301 - • Updated **astroid** to 2.5.3 Closes #2822, #4206, #4284 - • Add **consider-using-min-max-builtin** check for if statement which could be replaced by Python builtin min or max Closes #3406 - • Don't auto-enable postponed evaluation of type annotations with Python 3.10 - • Update **astroid** to 2.5.4 - • Add new extension **TypingChecker**. This optional checker can detect the use of deprecated typing aliases and can suggest the use of the alternative union syntax where possible. (For example, 'typing.Dict' can be replaced by 'dict', and 'typing.Unions' by '\|', etc.) Make sure to check the config options if you plan on using it! - • Reactivates old counts in report mode. Closes #3819 - • During detection of **inconsistent-return-statements** consider that **assert False** is a return node. Closes #4019 - • Run will not fail if score exactly equals **config.fail\_under**. - • Functions that never returns may declare **NoReturn** as type hints, so that **inconsistent-return-statements** is not emitted. Closes #4122, #4188 - • Improved protected access checks to allow access inside class methods Closes #1159 - • Fix issue with PEP 585 syntax and the use of **collections.abc.Set** - • Fix issue that caused class variables annotated with **typing.ClassVar** to be identified as class constants. Now, class variables annotated with **typing.Final** are identified as such. Closes #4277 - • Continuous integration with read the doc has been added. Closes #3850 - • Don't show **DuplicateBasesError** for attribute access - • Fix crash when checking **setup.cfg** for pylint config when there are non-ascii characters in there Closes #4328 - • Allow code flanked in backticks to be skipped by spellchecker Closes #4319 - • Allow Python tool directives (for black, flake8, zimports, isort, mypy, bandit, pycharm) at beginning of comments to be skipped by spellchecker Closes #4320 - • Fix issue that caused Emacs pylint to fail when used with tramp - • Improve check for invalid PEP 585 syntax inside functions if postponed evaluation of type annotations is enabled - • Improve check for invalid PEP 585 syntax as default function arguments ### What's New In Pylint 2.7 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights - • Python 3.6+ is now required. - • No more duplicate messages when using multiple jobs. - • Handling of the new typing provided by mypy 0.8 - • Reduced the number of false positives in general - • Reduced the occurrence of genuinely large recursion that went above system limit (See #3836, for a fix for pandas) ### New checkers - • Add **nan-comparison** check for comparison of NaN values - • Add support to **ignored-argument-names** in DocstringParameterChecker and adds **useless-param-doc** and **useless-type-doc** messages. - • Add **empty-comment** check for empty comments. - • Add **simplifiable-condition** check for extraneous constants in conditionals using and/or. - • Add **condition-evals-to-constant** check for conditionals using and/or that evaluate to a constant. - • Add **consider-using-generator** check for the use of list comprehension inside **any** or **all** function. ### Other Changes - • Fix false positive for **builtin-not-iterating** when **zip** or **map** receives iterable - • Fix linter multiprocessing pool shutdown which triggered warnings when ran in parallels with other pytest plugins. - • Enums are now required to be named in UPPER\_CASE by **invalid-name**. - • Fix bug that lead to duplicate messages when using **--jobs 2** or more. - • Adds option **check-protected-access-in-special-methods** in the ClassChecker to activate/deactivate **protected-access** message emission for single underscore prefixed attribute in special methods. - • **inconsistent-return-statements** message is now emitted if one of **try/except** statement is not returning explicitly while the other do. - • Fix false positive message **useless-super-delegation** when default keyword argument is a dictionary. - • Fix vulnerable regular expressions in **pyreverse**. The ambiguities of vulnerable regular expressions are removed, making the repaired regular expressions safer and faster matching. - • **len-as-conditions** is now triggered only for classes that are inheriting directly from list, dict, or set and not implementing the **\_\_bool\_\_** function, or from generators like range or list/dict/set comprehension. This should reduce the false positive for other classes, like pandas's DataFrame or numpy's Array. - • Fixes duplicate code detection for --jobs=2+ - • New option **allowed-redefined-builtins** defines variable names allowed to shadow builtins. - • Improved protected access checks to allow access inside class methods ### Full changelog ### What's New in Pylint 2.7.4? Release date: 2021-03-30 - • Fix a problem with disabled msgid not being ignored Closes #4265 - • Fix issue with annotated class constants Closes #4264 ### What's New in Pylint 2.7.3? Release date: 2021-03-29 - • Introduce logic for checking deprecated attributes in DeprecationMixin. - • Reduce usage of blacklist/whitelist terminology. Notably, **extension-pkg-allow-list** is an alternative to **extension-pkg-whitelist** and the message **blacklisted-name** is now emitted as **disallowed-name**. The previous names are accepted to maintain backward compatibility. - • Move deprecated checker to **DeprecatedMixin** Closes #4086 - • Bump **astroid** version to **2.5.2** - • Fix false positive for **method-hidden** when using private attribute and method Closes #3936 - • **use-symbolic-message-instead** now also works on legacy messages like **C0111** (**missing-docstring**). - • Remove unwanted print to stdout from **\_emit\_no\_member** - • Introduce a command-line option to specify pyreverse output directory Closes #4159 - • Fix issue with Enums and **class-attribute-naming-style=snake\_case** Closes #4149 - • Add **allowed-redefined-builtins** option for fine tuning **redefined-builtin** check. Closes #3263 - • Fix issue when executing with **python -m pylint** Closes #4161 - • Exempt **typing.TypedDict** from **too-few-public-methods** check. Closes #4180 - • Fix false-positive **no-member** for typed annotations without default value. Closes #3167 - • Add **--class-const-naming-style** for Enum constants and class variables annotated with **typing.ClassVar** Closes #4181 - • Fix astroid.Inference error for undefined-variables with **len()\`** Closes #4215 - • Fix column index on FIXME warning messages Closes #4218 - • Improve handling of assignment expressions, better edge case handling Closes #3763, #4238 - • Improve check if class is subscriptable PEP585 - • Fix documentation and filename handling of --import-graph - • Fix false-positive for **unused-import** on class keyword arguments Closes #3202 - • Fix regression with plugins on PYTHONPATH if latter is cwd Closes #4252 ### What's New in Pylint 2.7.2? Release date: 2021-02-28 - • Fix False Positive on **Enum.\_\_members\_\_.items()**, **Enum.\_\_members\_\_.values**, and **Enum.\_\_members\_\_.keys** Closes #4123 - • Properly strip dangerous sys.path entries (not just the first one) Closes #3636 - • Workflow and packaging improvements ### What's New in Pylint 2.7.1? Release date: 2021-02-23 - • Expose **UnittestLinter** in pylint.testutils - • Don't check directories starting with '.' when using register\_plugins Closes #4119 ### What's New in Pylint 2.7.0? Release date: 2021-02-21 - • Introduce DeprecationMixin for reusable deprecation checks. Closes #4049 - • Fix false positive for **builtin-not-iterating** when **map** receives iterable Closes #4078 - • Python 3.6+ is now required. - • Fix false positive for **builtin-not-iterating** when **zip** receives iterable - • Add **nan-comparison** check for NaN comparisons - • Bug fix for empty-comment message line number. Closes #4009 - • Only emit **bad-reversed-sequence** on dictionaries if below py3.8 Closes #3940 - • Handle class decorators applied to function. Closes #3882 - • Add check for empty comments - • Fix minor documentation issue in contribute.rst - • Enums are now required to be named in UPPER\_CASE by **invalid-name**. Closes #3834 - • Add missing checks for deprecated functions. - • Postponed evaluation of annotations are now recognized by default if python version is above 3.10 Closes #3992 - • Fix column metadata for anomalous backslash lints - • Drop support for Python 3.5 - • Add support for pep585 with postponed evaluation Closes #3320 - • Check alternative union syntax - PEP 604 Closes #4065 - • Fix multiple false positives with assignment expressions Closes #3347, #3953, #3865, #3275 - • Fix TypedDict inherit-non-class false-positive Python 3.9+ Closes #1927 - • Fix issue with nested PEP 585 syntax - • Fix issue with nested PEP 604 syntax - • Fix a crash in **undefined-variable** caused by chained attributes in metaclass Closes #3742 - • Fix false positive for **not-async-context-manager** when **contextlib.asynccontextmanager** is used Closes #3862 - • Fix linter multiprocessing pool shutdown (triggered warnings when ran in parallels with other pytest plugins) Closes #3779 - • Fix a false-positive emission of **no-self-use** and **unused-argument** for methods of generic structural types (*Protocol\[T\]*) Closes #3885 - • Fix bug that lead to duplicate messages when using **--jobs 2** or more. Closes #3584 - • Adds option **check-protected-access-in-special-methods** in the ClassChecker to activate/deactivate **protected-access** message emission for single underscore prefixed attribute in special methods. Closes #3120 - • Fix vulnerable regular expressions in **pyreverse** Closes #3811 - • **inconsistent-return-statements** message is now emitted if one of **try/except** statement is not returning explicitly while the other do. Closes #3468 - • Fix **useless-super-delegation** false positive when default keyword argument is a dictionary. Closes #3773 - • Fix a crash when a specified config file does not exist - • Add support to **ignored-argument-names** in DocstringParameterChecker and adds **useless-param-doc** and **useless-type-doc** messages. Closes #3800 - • Enforce docparams consistently when docstring is not present Closes #2738 - • Fix **duplicate-code** false positive when lines only contain whitespace and non-alphanumeric characters (e.g. parentheses, bracket, comma, etc.) - • Improve lint message for **singleton-comparison** with bools - • Fix spell-checker crash on indented docstring lines that look like # comments Closes #3786 - • Fix AttributeError in checkers/refactoring.py - • Improve sphinx directives spelling filter - • Fix a bug with postponed evaluation when using aliases for annotations. Closes #3798 - • Fix minor documentation issues - • Improve the performance of the line length check. - • Removed incorrect deprecation of **inspect.getfullargspec** - • Fix **signature-differs** false positive for functions with variadics Closes #3737 - • Fix a crash in **consider-using-enumerate** when encountering **range()** without arguments Closes #3735 - • **len-as-conditions** is now triggered only for classes that are inheriting directly from list, dict, or set and not implementing the **\_\_bool\_\_** function, or from generators like range or list/dict/set comprehension. This should reduce the false positives for other classes, like pandas's DataFrame or numpy's Array. Closes #1879 - • Fixes duplicate-errors not working with -j2+ Closes #3314 - • **generated-members** now matches the qualified name of members Closes #2498 - • Add check for bool function to **len-as-condition** - • Add **simplifiable-condition** check for extraneous constants in conditionals using and/or. - • Add **condition-evals-to-constant** check for conditionals using and/or that evaluate to a constant. Closes #3407 - • Changed setup.py to work with distlib \ Closes #3555 - • New check: **consider-using-generator** This check warns when a comprehension is used inside an **any** or **all** function, since it is unnecessary and should be replaced by a generator instead. Using a generator would be less code and way faster. Closes #3165 - • Add Github Actions to replace Travis and AppVeyor in the future ### What's New In Pylint 2.6 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights - • **bad-continuation** and **bad-whitespace** have been removed. **black** or another formatter can help you with this better than Pylint - • Added support for isort 5 ### New checkers - • Add **super-with-arguments** check for flagging instances of Python 2 style super calls. - • Add **raise-missing-from** check for exceptions that should have a cause. ### Other Changes - • **bad-continuation** and **bad-whitespace** have been removed. **black** or another formatter can help you with this better than Pylint - • The **no-space-check** option has been removed, it's no longer possible to consider empty line like a **trailing-whitespace** by using clever options. - • **mixed-indentation** has been removed, it is no longer useful since TabError is included directly in python3 - • Fix superfluous-parens / C0325 \<#superfluous-parens\> false-positive for the walrus operator - • Add support for both isort 4 and isort 5. If you have pinned isort 4 in your project requirements, nothing changes. If you use isort 5, though, note that the **known-standard-library** option is not interpreted the same in isort 4 and isort 5 (see *the migration guide in isort documentation* (no longer available) for further details). For compatibility's sake for most pylint users, the **known-standard-library** option in pylint now maps to **extra-standard-library** in isort 5. If you really want what **known-standard-library** now means in isort 5, you must disable the **wrong-import-order** check in pylint and run isort manually with a proper isort configuration file. ### Full changelog ### What's New in Pylint 2.6.1? Release date: 2021-02-16 - • Astroid version has been set as \< 2.5 Closes #4093 ### What's New in Pylint 2.6.0? Release date: 2020-08-20 - • Fix various scope-related bugs in **undefined-variable** checker Closes #1082, #3434, #3461 - • bad-continuation and bad-whitespace have been removed, black or another formatter can help you with this better than Pylint Closes #246, #289, #638, #747, #1148, #1179, #1943, #2041, #2301, #2304, #2944, #3565 - • The no-space-check option has been removed. It's no longer possible to consider empty line like a **trailing-whitespace** by using clever options Closes #1368 - • **missing-kwoa** is no longer emitted when dealing with overload functions Closes #3655 - • mixed-indentation has been removed, it is no longer useful since TabError is included directly in python3 Closes #2984 #3573 - • Add **super-with-arguments** check for flagging instances of Python 2 style super calls. - • Add an faq detailing which messages to disable to avoid duplicates w/ other popular linters - • Fix superfluous-parens / C0325 \<#superfluous-parens\> false-positive for the walrus operator Closes #3383 - • Fix **fail-under** not accepting floats - • Fix a bug with **ignore-docstrings** ignoring all lines in a module - • Fix **pre-commit** config that could lead to undetected duplicate lines of code - • Fix a crash in parallel mode when the module's filepath is not set Closes #3564 - • Add **raise-missing-from** check for exceptions that should have a cause. - • Support both isort 4 and isort 5. If you have pinned isort 4 in your project requirements, nothing changes. If you use isort 5, though, note that the **known-standard-library** option is not interpreted the same in isort 4 and isort 5 (see the migration guide in isort documentation for further details). For compatibility's sake for most pylint users, the **known-standard-library** option in pylint now maps to **extra-standard-library** in isort 5. If you really want what **known-standard-library** now means in isort 5, you must disable the **wrong-import-order** check in pylint and run isort manually with a proper isort configuration file. Closes #3722 - • Fix a crash caused by not guarding against **InferenceError** when calling **infer\_call\_result** Closes #3690 - • Fix a crash in parallel mode when the module's filepath is not set Closes #3564 ### What's New In Pylint 2.5 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights ### New checkers - • A new check **isinstance-second-argument-not-valid-type** was added. This check is emitted whenever **pylint** finds a call to the **isinstance** function with a second argument that is not a type. Such code is likely unintended as it will cause a TypeError to be thrown at runtime error. - • A new check **assert-on-string-literal** was added. This check is emitted whenever **pylint** finds an assert statement with a string literal as its first argument. Such assert statements are probably unintended as they will always pass. - • A new check **f-string-without-interpolation** was added. This check is emitted whenever **pylint** detects the use of an f-string without having any interpolated values in it, which means that the f-string can be a normal string. - • Multiple checks for invalid return types of protocol functions were added: - • **invalid-bool-returned**: **\_\_bool\_\_** did not return a bool - • **invalid-index-returned**: **\_\_index\_\_** did not return an integer - • **invalid-repr-returned)**: **\_\_repr\_\_** did not return a string - • **invalid-str-returned)**: **\_\_str\_\_** did not return a string - • **invalid-bytes-returned)**: **\_\_bytes\_\_** did not return a string - • **invalid-hash-returned)**: **\_\_hash\_\_** did not return an integer - • **invalid-length-hint-returned)**: **\_\_length\_hint\_\_** did not return a non-negative integer - • **invalid-format-returned)**: **\_\_format\_\_** did not return a string - • **invalid-getnewargs-returned)**: **\_\_getnewargs\_\_** did not return a tuple - • **invalid-getnewargs-ex-returned)**: **\_\_getnewargs\_ex\_\_** did not return a tuple of the form (tuple, dict) - • A new check **inconsistent-quotes** was added. This check is emitted when quotes delimiters (**"** and **'**) are not used consistently throughout a module. It allows avoiding unnecessary escaping, allowing, for example, **"Don't error"** in a module in which single-quotes otherwise delimit strings so that the single quote in **Don't** doesn't need to be escaped. - • A new check **non-str-assignment-to-dunder-name** was added to ensure that only strings are assigned to **\_\_name\_\_** attributes. ### Other Changes - • Configuration can be read from a setup.cfg or pyproject.toml file in the current directory. A setup.cfg must prepend pylintrc section names with **pylint.**, for example **\[pylint.MESSAGES CONTROL\]**. A pyproject.toml file must prepend section names with **tool.pylint.**, for example **\[tool.pylint.'MESSAGES CONTROL'\]**. These files can also be passed in on the command line. - • Add new **good-names-rgx** and **bad-names-rgx** to enable permitting or disallowing of names via regular expressions To enable better handling of permitted/disallowed names, we added two new config options: good-names-rgxs: a comma- separated list of regexes, that if a name matches will be exempt from naming-checking. bad-names-rgxs: a comma- separated list of regexes, that if a name matches will be always marked as a disallowed name. - • Mutable **collections.\*** are now flagged as dangerous defaults. - • Add new **--fail-under** flag for setting the threshold for the score to fail overall tests. If the score is over the fail-under threshold, pylint will complete SystemExit with value 0 to indicate no errors. - • Added a new option **notes-rgx** to make fixme warnings more flexible. Now either **notes** or **notes-rgx** option can be used to detect fixme warnings. - • Non-ASCII characters are now allowed by **invalid-name**. - • **pylint** no longer emits **invalid-name** for non-constants found at module level. Pylint was considering all module level variables as constants, which is not what PEP 8 is actually mandating. - • A new check **non-ascii-name** was added to detect identifiers with non-ASCII characters. - • Overloaded typing functions no longer trigger **no-self-use**, **unused-argument**, **missing-docstring** and similar checks that assumed that overloaded functions are normal functions. - • **python -m pylint** can no longer be made to import files from the local directory. - • A new command **--list-extensions** was added. This command lists all extensions present in **pylint.extensions**. - • Various false positives have been fixed which you can read more about in the Changelog files. - • Multiple types of string formatting are allowed in logging functions. The **logging-fstring-interpolation** message has been brought back to allow multiple types of string formatting to be used. The type of formatting to use is chosen through enabling and disabling messages rather than through the logging-format-style option. The fstr value of the logging-format-style option is not valid. ### Full changelog ### What's New in Pylint 2.5.3? Release date: 2020-06-8 - • Fix a regression where disable comments that have checker names with numbers in them are not parsed correctly Closes #3666 - • **property-with-parameters** properly handles abstract properties Closes #3600 - • **continue-in-finally** no longer emitted on Python 3.8 where it's now valid Closes #3612 - • Fix a regression where messages with dash are not fully parsed Closes #3604 - • In a TOML configuration file, it's now possible to use rich (non-string) types, such as list, integer or boolean instead of strings. For example, one can now define a *list* of message identifiers to enable like this: ``` enable = [ "use-symbolic-message-instead", "useless-suppression", ] ``` Closes #3538 - • Fix a regression where the score was not reported with multiple jobs Closes #3547 - • Protect against **AttributeError** when checking **cell-var-from-loop** Closes #3646 ### What's New in Pylint 2.5.2? Release date: 2020-05-05 - • **pylint.Run** accepts **do\_exit** as a deprecated parameter Closes #3590 ### What's New in Pylint 2.5.1? Release date: 2020-05-05 - • Fix a crash in **method-hidden** lookup for unknown base classes Closes #3527 - • Revert pylint.Run's **exit** parameter to **do\_exit** This has been inadvertently changed several releases ago to **do\_exit**. Closes #3533 - • **no-value-for-parameter** variadic detection has improved for assign statements Closes #3563 - • Allow package files to be properly discovered with multiple jobs Closes #3524 - • Allow linting directories without **\_\_init\_\_.py** which was a regression in 2.5. Closes #3528 ### What's New in Pylint 2.5.0? Release date: 2020-04-27 - • Fix a false negative for **undefined-variable** when using class attribute in comprehension. Closes #3494 - • Fix a false positive for **undefined-variable** when using class attribute in decorator or as type hint. Closes #511 Closes #1976 - • Remove HTML quoting of messages in JSON output. Closes #2769 - • Adjust the **invalid-name** rule to work with non-ASCII identifiers and add the **non-ascii-name** rule. Closes #2725 - • Positional-only arguments are taken in account for **useless-super-delegation** - • **unidiomatic-typecheck** is no longer emitted for **in** and **not in** operators Closes #3337 - • Positional-only argument annotations are taken in account for **unused-import** Closes #3462 - • Add a command to list available extensions. - • Allow used variables to be properly consumed when different checks are enabled / disabled Closes #3445 - • Fix dangerous-default-value / W0102 \<#dangerous-default-value\> rule to account for keyword argument defaults Closes #3373 - • Fix a false positive of **self-assigning-variable** on tuple unpacking. Closes #3433 - • **no-self-use** is no longer emitted for typing stubs. Closes #3439 - • Fix a false positive for **undefined-variable** when **\_\_class\_\_** is used Closes #3090 - • Emit **invalid-name** for variables defined in loops at module level. Closes #2695 - • Add a check for cases where the second argument to **isinstance** is not a type. Closes #3308 - • Add 'notes-rgx' option, to be used for fixme check. Closes #2874 - • **function-redefined** exempts function redefined on a condition. Closes #2410 - • **typing.overload** functions are exempted from docstring checks Closes #3350 - • Emit **invalid-overridden-method** for improper async def overrides. Closes #3355 - • Do not allow **python -m pylint ...** to import user code **python -m pylint ...** adds the current working directory as the first element of **sys.path**. This opens up a potential security hole where **pylint** will import user level code as long as that code resides in modules having the same name as stdlib or pylint's own modules. Closes #3386 - • Add **dummy-variables-rgx** option for **\_redeclared-assigned-name** check. Closes #3341 - • Fixed graph creation for relative paths - • Add a check for asserts on string literals. Closes #3284 - • **not in** is considered iterating context for some of the Python 3 porting checkers. - • A new check **inconsistent-quotes** was added. - • Add a check for non string assignment to \_\_name\_\_ attribute. Closes #583 - • **\_\_pow\_\_**, **\_\_imatmul\_\_**, **\_\_trunc\_\_**, **\_\_floor\_\_**, and **\_\_ceil\_\_** are recognized as special method names. Closes #3281 - • Added errors for protocol functions when invalid return types are detected. E0304 (invalid-bool-returned / E0304 \<#invalid-bool-returned\>): \_\_bool\_\_ did not return a bool E0305 (invalid-index-returned / E0305 \<#invalid-index-returned\>): \_\_index\_\_ did not return an integer E0306 (invalid-repr-returned / E0306 \<#invalid-repr-returned\>): \_\_repr\_\_ did not return a string E0307 (invalid-str-returned / E0307 \<#invalid-str-returned\>): \_\_str\_\_ did not return a string E0308 (invalid-bytes-returned / E0308 \<#invalid-bytes-returned\>): \_\_bytes\_\_ did not return a string E0309 (invalid-hash-returned / E0309 \<#invalid-hash-returned\>): \_\_hash\_\_ did not return an integer E0310 (invalid-length-hint-returned / E0310 \<#invalid-length-hint-returned\>): \_\_length\_hint\_\_ did not return a non-negative integer E0311 (invalid-format-returned / E0311 \<#invalid-format-returned\>): \_\_format\_\_ did not return a string E0312 (invalid-getnewargs-returned / E0312 \<#invalid-getnewargs-returned\>): \_\_getnewargs\_\_ did not return a tuple E0313 (invalid-getnewargs-ex-returned / E0313 \<#invalid-getnewargs-ex-returned\>): \_\_getnewargs\_ex\_\_ did not return a tuple of the form (tuple, dict) Closes #560 - • **missing-\*-docstring** can look for **\_\_doc\_\_** assignments. Closes #3301 - • **undefined-variable** can now find undefined loop iterables Closes #498 - • **safe\_infer** can infer a value as long as all the paths share the same type. Closes #2503 - • Add a --fail-under \ flag, also configurable in a .pylintrc file. If the final score is more than the specified score, it's considered a success and pylint exits with exitcode 0. Otherwise, it's considered a failure and pylint exits with its current exitcode based on the messages issued. Closes #2242 - • Don't emit **line-too-long** for multilines when **disable=line-too-long** comment stands at their end Closes #2957 - • Fixed an **AttributeError** caused by improper handling of **dataclasses** inference in **pyreverse** Closes #3256 - • Do not exempt bare except from **undefined-variable** and similar checks If a node was wrapped in a **TryExcept**, **pylint** was taking a hint from the except handler when deciding to emit or not a message. We were treating bare except as a fully fledged ignore but only the corresponding exceptions should be handled that way (e.g. **NameError** or **ImportError**) Closes #3235 - • No longer emit **assignment-from-no-return** when a function only raises an exception Closes #3218 - • Allow import aliases to exempt **import-error** when used in type annotations. Closes #3178 - • **Ellipsis\` is exempted from \`\`multiple-statements** for function overloads. Closes #3224 - • No longer emit **invalid-name** for non-constants found at module level. Pylint was taking the following statement from PEP-8 too far, considering all module level variables as constants, which is not what the statement is saying: *Constants are usually defined on a module level and written in* *all capital letters with underscores separating words.* Closes #3111 Closes #3132 - • Allow **implicit-str-concat-in-sequence** to be emitted for string juxtaposition Closes #3030 - • **implicit-str-concat-in-sequence** was renamed **implicit-str-concat** - • The **json** reporter no longer bypasses **redirect\_stdout**. Closes #3227 - • Move **NoFileError**, **OutputLine**, **FunctionalTestReporter**, **FunctionalTestFile**, **LintModuleTest** and related methods from **test\_functional.py** to **pylint.testutils** to help testing for 3rd party pylint plugins. - • Can read config from a setup.cfg or pyproject.toml file. Closes #617 - • Fix exception-escape false positive with generators Closes #3128 - • **inspect.getargvalues** is no longer marked as deprecated. - • A new check **f-string-without-interpolation** was added Closes #3190 - • Flag mutable **collections.\*** utilities as dangerous defaults Closes #3183 - • **docparams** extension supports multiple types in raises sections. Multiple types can also be separated by commas in all valid sections. Closes #2729 - • Allow parallel linting when run under Prospector - • Fixed false positives of **method-hidden** when a subclass defines the method that is being hidden. Closes #414 - • Python 3 porting mode is 30-50% faster on most codebases - • Python 3 porting mode no longer swallows syntax errors Closes #2956 - • Pass the actual PyLinter object to sub processes to allow using custom PyLinter classes. PyLinter object (and all its members except reporter) needs to support pickling so the PyLinter object can be passed to worker processes. - • Clean up setup.py Make pytest-runner a requirement only if running tests, similar to McCabe. Clean up the setup.py file, resolving a number of warnings around it. - • Handle SyntaxError in files passed via **--from-stdin** option Pylint no longer outputs a traceback, if a file, read from stdin, contains a syntaxerror. - • Fix uppercase style to disallow 3+ uppercase followed by lowercase. - • Fixed **undefined-variable** and **unused-import** false positives when using a metaclass via an attribute. Closes #1603 - • Emit **unused-argument** for functions that partially uses their argument list before raising an exception. Closes #3246 - • Fixed **broad\_try\_clause** extension to check try/finally statements and to check for nested statements (e.g., inside of an **if** statement). - • Recognize classes explicitly inheriting from **abc.ABC** or having an **abc.ABCMeta** metaclass as abstract. This makes them not trigger W0223. Closes #3098 - • Fix overzealous **arguments-differ** when overridden function uses variadics No message is emitted if the overriding function provides positional or keyword variadics in its signature that can feasibly accept and pass on all parameters given by the overridden function. Closes #1482 Closes #1553 - • Multiple types of string formatting are allowed in logging functions. The **logging-fstring-interpolation** message has been brought back to allow multiple types of string formatting to be used. Closes #3361 ### What's New In Pylint 2.4 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights ### New checkers - • **import-outside-toplevel** This check warns when modules are imported from places other than a module toplevel, e.g. inside a function or a class. - • Added a new check, **consider-using-sys-exit** This check is emitted when we detect that a quit() or exit() is invoked instead of sys.exit(), which is the preferred way of exiting in program. Closes #2925 - • Added a new check, **arguments-out-of-order** This check warns if you have arguments with names that match those in a function's signature but you are passing them in to the function in a different order. Closes #2975 - • Added new checks, **no-else-break** and **no-else-continue** These checks highlight unnecessary **else** and **elif** blocks after **break** and **continue** statements. Closes #2327 - • Added **unnecessary-comprehension** that detects unnecessary comprehensions. This check is emitted when **pylint** finds list-, set- or dict-comprehensions, that are unnecessary and can be rewritten with the list-, set- or dict-constructors. Closes #2905 - • Added a new check, **invalid-overridden-method** This check is emitted when we detect that a method is overridden as a property or a property is overridden as a method. This can indicate a bug in the application code that will trigger a runtime error. Closes #2670 - • Added a new check, **redeclared-assigned-name** This check is emitted when **pylint** detects that a name was assigned one or multiple times in the same assignment, which indicate a potential bug. Closes #2898 - • Added a new check, **self-assigning-variable** This check is emitted when we detect that a variable is assigned to itself, which might indicate a potential bug in the code application. For example, the following would raise this warning: ``` def new_a(attr, attr2): a_inst = Aclass() a_inst.attr2 = attr2 # should be: a_inst.attr = attr, but have a typo attr = attr return a_inst ``` Closes #2930 - • Added a new check **property-with-parameters** which detects when a property has more than a single argument. Closes #3006 - • Added **subprocess-run-check** to handle subprocess.run without explicitly set **check** keyword. Closes #2848 - • We added a new check message **dict-iter-missing-items**. This is emitted when trying to iterate through a dict in a for loop without calling its .items() method. Closes #2761 - • We added a new check message **missing-parentheses-for-call-in-test**. This is emitted in case a call to a function is made inside a test but it misses parentheses. - • A new check **class-variable-slots-conflict** was added. This check is emitted when **pylint** finds a class variable that conflicts with a slot name, which would raise a **ValueError** at runtime. For example, the following would raise an error: ``` class A: __slots__ = ('first', 'second') first = 1 ``` - • A new check **preferred-module** was added. This check is emitted when **pylint** finds an imported module that has a preferred replacement listed in **preferred-modules**. For example, you can set the preferred modules as **xml:defusedxml,json:ujson** to make **pylint** suggest using **defusedxml** instead of **xml** and **ujson** rather than **json**. - • A new extension **broad\_try\_clause** was added. This extension enforces a configurable maximum number of statements inside of a try clause. This facilitates enforcing PEP 8's guidelines about try / except statements and the amount of code in the try clause. You can enable this extension using **--load-plugins=pylint.extensions.broad\_try\_clause** and you can configure the amount of statements in a try statement using **--max-try-statements**. ### Other Changes - • Don't emit **protected-access** when a single underscore prefixed attribute is used inside a special method Closes #1802 - • **len-as-condition** now only fires when a **len(x)** call is made without an explicit comparison. The message and description accompanying this checker has been changed reflect this new behavior, by explicitly asking to either rely on the fact that empty sequence are false or to compare the length with a scalar. OK: ``` if len(x) == 0: pass while not len(x) == 0: pass assert len(x) > 5, message ``` KO: ``` if not len(x): pass while len(x) and other_cond: pass assert len(x), message ``` - • A file is now read from stdin if the **--from-stdin** flag is used on the command line. In addition to the **--from-stdin** flag a (single) file name needs to be specified on the command line, which is needed for the report. - • The checker for ungrouped imports is now more permissive. The import can now be sorted alphabetically by import style. This makes pylint compatible with isort. The following imports do not trigger an **ungrouped-imports** anymore ``` import unittest import zipfile from unittest import TestCase from unittest.mock import MagicMock ``` - • The checker for missing return documentation is now more flexible. The following does not trigger a **missing-return-doc** anymore ``` def my_func(self): """This is a docstring. Returns ------- :obj:`list` of :obj:`str` List of strings """ return ["hi", "bye"] #@ ``` - • **signature-mutators** CLI and config option was added. With this option, users can choose to ignore **too-many-function-args**, **unexpected-keyword-arg**, and **no-value-for-parameter** for functions decorated with decorators that change the signature of a decorated function. For example a test may want to make use of hypothesis. Adding **hypothesis.extra.numpy.arrays** to **signature\_mutators** would mean that **no-value-for-parameter** would not be raised for: ``` @given(img=arrays(dtype=np.float32, shape=(3, 3, 3, 3))) def test_image(img): ... ``` - • Allow the option of f-strings as a valid logging string formatting method. **logging-fstring--interpolation** has been merged into **logging-format-interpolation** to allow the **logging-format-style** option to control which logging string format style is valid. To allow this, a new **fstr** value is valid for the **logging-format-style** option. - • **--list-msgs-enabled** command was added. When enabling/disabling several messages and groups in a config file, it can be unclear which messages are actually enabled and which are disabled. This new command produces the final resolved lists of enabled/disabled messages, sorted by symbol but with the ID provided for use with **--help-msg**. ### Full changelog ### What's New in Pylint 2.4.4? Release date: 2019-11-13 - • Exempt all the names found in type annotations from **unused-import** The previous code was assuming that only **typing** names need to be exempted, but we need to do that for the rest of the type comment names as well. Closes #3112 - • Relax type import detection for names that do not come from the **typing** module Closes #3191 ### What's New in Pylint 2.4.3? Release date: 2019-10-18 - • Fix an issue with **unnecessary-comprehension** in comprehensions with additional repacking of elements. Closes #3148 - • **import-outside-toplevel** is emitted for **ImportFrom** nodes as well. Closes #3175 - • Do not emit **no-method-argument** for functions using positional only args. Closes #3161 - • **consider-using-sys-exit** is no longer emitted when **exit** is imported in the local scope. Closes #3147 - • **invalid-overridden-method** takes **abc.abstractproperty** in account Closes #3150 - • Fixed **missing-yield-type-doc** getting incorrectly raised when a generator does not document a yield type but has a type annotation. Closes #3185 - • **typing.overload** functions are exempted from **too-many-function-args** Closes #3170 ### What's New in Pylint 2.4.2? Release date: 2019-09-30 - • **ignored-modules** can skip submodules. Closes #3135 - • **self-assigning-variable** skips class level assignments. Closes #2930 - • **consider-using-sys-exit** is exempted when **exit()** is imported from **sys** Closes #3145 - • Exempt annotated assignments without variable from **class-variable-slots-conflict** Closes #3141 - • Fix **utils.is\_error** to account for functions returning early. This fixes a false negative with **unused-variable** which was no longer triggered when a function raised an exception as the last instruction, but the body of the function still had unused variables. Closes #3028 ### What's New in Pylint 2.4.1? Release date: 2019-09-25 - • Exempt type checking definitions defined in both clauses of a type checking guard Closes #3127 - • Exempt type checking definitions inside the type check guard In a7f236528bb3758886b97285a56f3f9ce5b13a99 we added basic support for emitting **used-before-assignment** if a variable was only defined inside a type checking guard (using **TYPE\_CHECKING** variable from *typing*) Unfortunately that missed the case of using those type checking imports inside the guard itself, which triggered spurious used-before-assignment / E0601 \<#used-before-assignment\> errors. Closes #3119 - • Require astroid \>= 2.3 to avoid any compatibility issues. ### What's New in Pylint 2.4.0? Release date: 2019-09-24 - • New check: **import-outside-toplevel** This check warns when modules are imported from places other than a module toplevel, e.g. inside a function or a class. - • Handle inference ambiguity for **invalid-format-index** Closes #2752 - • Removed Python 2 specific checks such as **relative-import**, **invalid-encoded-data**, **missing-super-argument**. - • Support forward references for **function-redefined** check. Closes #2540 - • Handle redefinitions in case of type checking imports. Closes #2834 - • Added a new check, **consider-using-sys-exit** This check is emitted when we detect that a quit() or exit() is invoked instead of sys.exit(), which is the preferred way of exiting in program. Closes #2925 - • **useless-suppression** check now ignores **cyclic-import** suppressions, which could lead to false positives due to incomplete context at the time of the check. Closes #3064 - • Added new checks, **no-else-break** and **no-else-continue** These checks highlight unnecessary **else** and **elif** blocks after **break** and **continue** statements. Closes #2327 - • Don't emit **protected-access** when a single underscore prefixed attribute is used inside a special method Closes #1802 - • Fix the "statement" values in the PyLinter's stats reports by module. - • Added a new check, **invalid-overridden-method** This check is emitted when we detect that a method is overridden as a property or a property is overridden as a method. This can indicate a bug in the application code that will trigger a runtime error. Closes #2670 - • Added a new check, **arguments-out-of-order** This check warns if you have arguments with names that match those in a function's signature but you are passing them in to the function in a different order. Closes #2975 - • Added a new check, **redeclared-assigned-name** This check is emitted when **pylint** detects that a name was assigned one or multiple times in the same assignment, which indicate a potential bug. Closes #2898 - • Ignore lambda calls with variadic arguments without a context. Inferring variadic positional arguments and keyword arguments will result into empty Tuples and Dicts, which can lead in some cases to false positives with regard to no-value-for-parameter / E1120 \<#no-value-for-parameter\>. In order to avoid this, until we'll have support for call context propagation, we're ignoring such cases if detected. We already did that for function calls, but the previous fix was not taking in consideration **lambdas** Closes #2918 - • Added a new check, **self-assigning-variable**. This check is emitted when we detect that a variable is assigned to itself, which might indicate a potential bug in the code application. Closes #2930 - • Added a new check, **property-with-parameters**. This check is emitted when we detect that a defined property also has parameters, which are useless. Closes #3006 - • Excluded protocol classes from a couple of checks. Closes #3002. - • Add a check **unnecessary-comprehension** that detects unnecessary comprehensions. This check is emitted when **pylint** finds list-, set- or dict-comprehensions, that are unnecessary and can be rewritten with the list-, set- or dict-constructors. Closes #2905 - • Excluded PEP 526 instance and class variables from **no-member**. Closes #2945 - • Excluded **attrs** from **too-few-public-methods** check. Closes #2988. - • **unused-import** emitted for the right import names in function scopes. Closes #2928 - • Dropped support for Python 3.4. - • **assignment-from-no-return** not triggered for async methods. Closes #2902 - • Don't emit **attribute-defined-outside-init** for variables defined in setters. Closes #409 - • Syntax errors report the column number. Closes #2914 - • Support fully qualified typing imports for type annotations. Closes #2915 - • Exclude **\_\_dict\_\_** from **attribute-defined-outside-init** - • Fix pointer on spelling check when the error are more than one time in the same line. Closes #2895 - • Fix crash happening when parent of called object cannot be determined - • Allow of in **GoogleDocstring.re\_multiple\_type** - • Added **subprocess-run-check** to handle subrocess.run without explicitly set **check** keyword. Closes #2848 - • When we can't infer bare except handlers, skip **try-except-raise** Closes #2853 - • Handle more **unnecessary-lambda** cases when dealing with additional kwargs in wrapped calls Closes #2845 - • Better postponed evaluation of annotations handling Closes #2847 - • Support postponed evaluation of annotations for variable annotations. Closes #2838 - • **epylint.py\_run** defaults to **python** in case the current executable is not a Python one. Closes #2837 - • Ignore raw docstrings when running Similarities checker with **ignore-docstrings=yes** option - • Fix crash when calling **inherit\_from\_std\_ex** on a class which is its own ancestor Closes #2680 - • Added a new check that warns the user if a function call is used inside a test but parentheses are missing. Closes #2658 - • **len-as-condition** now only fires when a **len(x)** call is made without an explicit comparison The message and description accompanying this checker has been changed reflect this new behavior, by explicitly asking to either rely on the fact that empty sequence are false or to compare the length with a scalar. Closes #2684 - • Add **preferred-module** checker that notify if an import has a replacement module that should be used. This check is emitted when **pylint** finds an imported module that has a preferred replacement listed in **preferred-modules**. - • **assigning-non-slot** not emitted for classes with unknown base classes. Closes #2807 - • **old-division** is not emitted for non-Const nodes. Closes #2808 - • Added method arguments to the dot writer for pyreverse. Closes #2139 - • Support for linting file from stdin. IDEs may benefit from the support for linting from an in-memory file. Closes #1187 - • Added a new check **class-variable-slots-conflict** This check is emitted when **pylint** finds a class variable that conflicts with a slot name, which would raise a **ValueError** at runtime. - • Added new check: dict-iter-missing-items / E1141 \<#dict-iter-missing-items\> (E1141) Closes #2761 - • Fix issue with pylint name in output of python -m pylint --version Closes #2764 - • Relicense logo material under the CC BY-SA 4.0 license. - • Skip **if** expressions from f-strings for the **check\_elif** checker Closes #2816 - • C0412 (ungrouped-import) is now compatible with isort. Closes #2806 - • Added new extension to detect too much code in a try clause Closes #2877 - • **signature-mutators** option was added. With this option, users can choose to ignore **too-many-function-args**, **unexpected-keyword-arg**, and **no-value-for-parameter** for functions decorated with decorators that change the signature of a decorated function. Closes #259 - • Fixed a pragma comment on its own physical line being ignored when part of a logical line with the previous physical line. Closes #199 - • Fixed false **undefined-loop-variable** for a function defined in the loop, that uses the variable defined in that loop. Closes #202 - • Fixed **unused-argument** and **function-redefined** getting raised for functions decorated with **typing.overload**. Closes #1581 - • Fixed a false positive with **consider-using-dict-comprehension** for constructions that can't be converted to a comprehension Closes #2963 - • Added **\_\_post\_init\_\_** to **defining-attr-methods** in order to avoid **attribute-defined-outside-init** in dataclasses. Closes #2581 - • Changed description of W0199 to use the term 2-item-tuple instead of 2-uple. - • Allow a **.** as a prefix for Sphinx name resolution. - • Checkers must now keep a 1 to 1 relationship between "msgid" (ie: C1234) and "symbol" (i.e. : human-readable-symbol) - • In checkers, an old\_names can now be used for multiple new messages and pylint is now a little faster It means if you do a partial old\_names for a message definition an exception will tell you that you must rename the associated identification. - • Allow the choice of f-strings as a valid way of formatting logging strings. Closes #2395 - • Added **--list-msgs-enabled** command to list all enabled and disabled messages given the current RC file and command line arguments. ### What's New In Pylint 2.3 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights - • This release improves the performance of the 2.X series after it was affected by a performance regression a couple of releases ago. ### New checkers - • We added a new check message **wrong-exception-operation**. This is emitted when an operation is done against an exception, but the operation is not valid for the exception in question. Usually emitted when having binary operations between exceptions in except handlers. Closes #2494 - • We added a new **no-else-raise** warning similar to **no-else-return** Closes #2558 - • We added a new option **check-str-concat-over-line-jumps** to check **implicit-str-concat-in-sequence** over multiple lines. ### Other Changes Quite a lot of bug fixes and improvements went into this release, here's a handful of them. For the full changes, check the full changelog. - • We no longer emit **\*-not-iterating** checks for builtins consumed by **itertools** - • We fixed some false positives for **no-self-argument** and **unsubscriptable-object** when using **\_\_class\_getitem\_\_** (new in Python 3.7) - • **pylint** now supports **Ellipsis** as a synonym for **pass** statements. - • **fixme** gets triggered only on comments. - • **pylint** exempts starred unpacking from **\*-not-iterating** Python 3 checks. - • **compare-to-zero** is now less zealous by checking against equality and identity. *\`\`yield from\`\` is exempted from \`\`*-not-iterating\`\` Python 3 checks. - • A false positive with **not-async-context-manager** caused by not understanding **contextlib.asynccontextmanager** was fixed. - • We refactored **bad-reversed-sequence** to account for more objects that can define **\_\_reversed\_\_**. - • **no-member** is now emitted for enums when they lack a member. - • Plugins can now use the **load\_configuration()** hook. This hook is executed after configuration is loaded to prevent overwriting plugin specific configuration via user-based configuration. - • There's a new command line option **list-groups** for listing all the check groups **pylint** knows about. This is useful to know what groups you can disable or enable individually. ### Full changelog ### What's New in Pylint 2.3.0? Release date: 2019-02-27 - • Protect against **NonDeducibleTypeHierarchy** when calling semi-private **is\_subtype** **astroid.helpers.is\_subtype** raises **NonDeducibleTypeHierarchy** when it cannot infer the base classes of the given types, but that makes sense in its context given that the method is mostly used to inform the inference process about the hierarchy of classes. Doesn't make that much sense for **pylint** itself, which is why we're handling the exception here, rather than in **astroid** Closes pylint-dev/astroid#644 - • Added a new command line option **list-groups** for listing all the check groups **pylint** knows about. - • Allow **BaseException** for emitting **broad-except**, just like **Exception**. Closes #2741 - • Fixed a crash that occurred for **bad-str-strip-call** when **strip()** received **None** Closes #2743 - • Don't emit **\*-not-iterating** checks for builtins consumed by **itertools** Closes #2731 - • Fix a crash caused by iterating over **Uninferable** in a string formatting check. Closes #2727 - • Fixed false positives for **no-self-argument** and **unsubscriptable-object** when using **\_\_class\_getitem\_\_** (new in Python 3.7) Closes #2416 - • Support **Ellipsis** as a synonym for **pass** statements. Closes #2718 - • **fixme** gets triggered only on comments. Closes #2321 - • Fixed a false positive for **unused-variable** and **nonlocal** assignments Closes #2671 - • Added **load\_configuration()** hook for plugins New optional hook for plugins is added: **load\_configuration()**. This hook is executed after configuration is loaded to prevent overwriting plugin specific configuration via user-based configuration. Closes #2635 - • Fix missing-raises-doc / W9006 \<#missing-raises-doc\> false positive (W9006) Closes #1502 - • Exempt starred unpacking from **\*-not-iterating** Python 3 checks Closes #2651 - • Make **compare-to-zero** less zealous by checking against equality and identity Closes #2645 - • Add **no-else-raise** warning (R1720) Closes #2558 - • Exempt **yield from** from **\*-not-iterating** Python 3 checks. Closes #2643 - • Fix incorrect generation of **no-else-return** warnings (R1705) Fixed issue where **if** statements with nested **if** statements were incorrectly being flagged as **no-else-return** in some cases and not being flagged as **no-else-return** in other cases. Added tests for verification and updated pylint source files to eliminate newly exposed warnings. - • Fix false positive with **not-async-context-manager** caused by not understanding **contextlib.asynccontextmanager** Closes #2440 - • Refactor **bad-reversed-sequence** to account for more objects that can define **\_\_reversed\_\_** One such object would be an enum class, for which **\_\_reversed\_\_** yields each individual enum. As such, the check for **bad-reversed-sequence** needs to not differentiate between classes and instances when it comes for checking of **\_\_reversed\_\_** presence. Closes #2598 - • Added **wrong-exception-operation** Used when an operation is done against an exception, but the operation is not valid for the exception in question. Usually emitted when having binary operations between exceptions in except handlers. Closes #2494 - • **no-member** is emitted for enums when they lack a member Previously we weren't doing this because we detected a **\_\_getattr\_\_** implementation on the **Enum** class (and this check is skipped for classes with **\_\_getattr\_\_**), but that is fine for Enums, given that they are inferred in a customised way in astroid. Closes #2565 - • Generalize **chained-comparison** Previous version incorrectly detects *a \< b \< c and b \< d* and fails to detect *a \< b \< c and c \< d*. - • Avoid popping \_\_main\_\_ when using multiple jobs Closes #2689 - • Add a new option 'check-str-concat-over-line-jumps' to check implicit-str-concat-in-sequence / W1403 \<#implicit-str-concat-in-sequence\>' - • Fixes for the new style logging format linter. The number of arguments was not handled properly, leading to an always successful check. - • Fix false positive **not-callable** for uninferable properties. - • Fix false positive **useless-else-on-loop** if the break is deep in the else of an inner loop. - • Minor improvements to the help text for a few options. ### What's New In Pylint 2.2 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights ### New checkers - • String checker now reports format string type mismatches. - • **duplicate-string-formatting-argument** was added for detecting duplicate string formatting arguments that should be passed instead as named arguments. - • **logging-format-style** is a new option for the logging checker for usage of str.format() style format strings in calls to loggers. It accepts two options: **--logging-format-style=old** for using *%* style formatting, which is the assumed default, and **--logging-format-style=new** for using *{}* style formatting. - • **implicit-str-concat-in-sequence** detects string concatenation inside lists, sets & tuples. Example of code that would generate such warning: ``` woops = ('a', 'b' 'c') ``` ### Other Changes - • **try-except-raise** checker now handles multilevel inheritance hirerachy for exceptions correctly. Closes #2484 - • Ignore import x.y.z as z cases for checker **useless-import-alias**. - • **unnecessary-pass** is now also emitted when a function or class contains only docstring and pass statement, in which case, docstring is enough for empty definition. - • Fix false positive **undefined-variable** and **used-before-assignment** with nonlocal keyword usage. - • Fix exceptions being raised when one of the params is not a ClassDef for **checkers.utils.is\_subclass\_of**. - • **pylint** now picks the latest value from the inferred values of the exception that gets raised, when looking for **raising-non-exception**. This helps when reusing a variable name for multiple types, since **pylint** was picking just the first inferred value, leading to spurious false positives. Closes #2431 - • **pylint** used to emit a **not-an-iterable** error when looking at coroutines built with **asyncio.coroutine**. This is no longer the case as we handle coroutines explicitly. Closes #996 - • **pylint** used to emit an **unused-variable** error if unused import was found in the function. Now instead of **unused-variable**, **unused-import** is emitted. Closes #2421 ### Full changelog ### What's New in Pylint 2.2.2? Release date: 2018-11-28 - • Change the **logging-format-style** to use name identifier instead of their corresponding Python identifiers This is to prevent users having to think about escaping the default value for **logging-format-style** in the generated config file. Also our config parsing utilities don't quite support escaped values when it comes to **choices** detection, so this would have needed various hacks around that. Closes #2614 ### What's New in Pylint 2.2.1? Release date: 2018-11-27 - • Fix a crash caused by **implicit-str-concat-in-sequence** and multi-bytes characters. Closes #2610 ### What's New in Pylint 2.2? Release date: 2018-11-25 - • Consider **range()** objects for **undefined-loop-variable** leaking from iteration. Closes #2533 - • **deprecated-method** can use the attribute name for identifying a deprecated method Previously we were using the fully qualified name, which we still do, but the fully qualified name for some **unittest** deprecated aliases leads to a generic deprecation function. Instead on relying on that, we now also rely on the attribute name, which should solve some false positives. Closes #1653 Closes #1946 - • Fix compatibility with changes to stdlib tokenizer. - • **pylint** is less eager to consume the whole line for pragmas Closes #2485 - • Obtain the correct number of CPUs for virtualized or containerized environments. Closes #2519 - • Change **unbalanced-tuple-unpacking** back to a warning. It used to be a warning until a couple of years ago, after it was promoted to an error. But the check might be suggesting the wrong thing in some cases, for instance when checking against **sys.argv** which cannot be known at static analysis time. Given it might rely on potential unknown data, it's best to have it as a warning. Closes #2522 - • Remove **enumerate** usage suggestion when defining **\_\_iter\_\_** (C0200) Closes #2477 - • Emit **too-many-starred-assignment** only when the number of Starred nodes is per assignment elements Closes #2513 - • **try-except-raise** checker now handles multilevel inheritance hirerachy for exceptions correctly. Closes #2484 - • Add a new check, **simplifiable-if-expression** for expressions like **True if cond else False**. Closes #2487 - • **too-few-public-methods** is not reported for **typing.NamedTuple** Closes #2459 - • **\`too-few-public-methods** is not reported for dataclasses created with options. Closes #2488 - • Remove wrong modules from 'bad-python3-import'. Closes #2453 - • The **json** reporter prints an empty list when no messages are emitted Closes #2446 - • Add a new check, **duplicate-string-formatting-argument** This new check is emitted whenever a duplicate string formatting argument is found. Closes #497 - • **assignment-from-no-return** is not emitted for coroutines. Closes #1715 - • Report format string type mismatches. - • **consider-using-ternary** and **simplified-boolean-expression** no longer emit for sequence based checks Closes #2473 - • Handle **AstroidSyntaxError** when trying to import a module. Closes #2313 - • Allow **\_\_module\_\_** to be redefined at a class level. Closes #2451 - • **pylint** used to emit an **unused-variable** error if unused import was found in the function. Now instead of **unused-variable**, **unused-import** is emitted. Closes #2421 - • Handle asyncio.coroutine when looking for **not-an-iterable** check. Closes #996 - • The **locally-enabled** check is gone. Closes #2442 - • Infer decorated methods when looking for method-hidden Closes #2369 - • Pick the latest value from the inferred values when looking for **raising-non-exception** Closes #2431 - • Extend the TYPE\_CHECKING guard to TYPE\_CHECKING name as well, not just the attribute Closes #2411 - • Ignore import x.y.z as z cases for checker **useless-import-alias**. Closes #2309 - • Fix false positive **undefined-variable** and **used-before-assignment** with nonlocal keyword usage. Closes #2049 - • Stop **protected-access** exception for missing class attributes - • Don't emit **assignment-from-no-return** for decorated function nodes Closes #2385 - • **unnecessary-pass** is now also emitted when a function or class contains only docstring and pass statement. In Python, stubbed functions often have a body that contains just a single **pass** statement, indicating that the function doesn't do anything. However, a stubbed function can also have just a docstring, and function with a docstring and no body also does nothing. Closes #2208 - • **duplicate-argument-name** is emitted for more than one duplicate argument per function Closes #1712 - • Allow double indentation levels for more distinguishable indentations Closes #741 - • Consider tuples in exception handler for **try-except-raise**. Closes #2389 - • Fix astroid.ClassDef check in checkers.utils.is\_subclass\_of - • Fix wildcard imports being ignored by the import checker - • Fix external/internal distinction being broken in the import graph - • Fix wildcard import check not skipping **\_\_init\_\_.py** Closes #2430 - • Add new option to logging checker, **logging\_format\_style** - • Fix --ignore-imports to understand multi-line imports Closes #1422 Closes #2019 - • Add a new check 'implicit-str-concat-in-sequence' to spot string concatenation inside lists, sets & tuples. - • **literal-comparison** is now emitted for 0 and 1 literals. ### What's New In Pylint 2.1 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights - • This release mostly includes fixes for bugs found after the launch of 2.0. ### New checkers - • A new check was added, **misplaced-format-function**. This message is emitted when pylint detects that a format function is called on non str object. This can occur due to wrong placement of closing bracket, e.g ``` print('value: {}').format(123) # bad print('value: {}'.format(123)) # good ``` ### Other Changes - • **try-except-raise** check was demoted from an error to a warning, as part of issue #2323. - • Correctly handle the new name of the Python implementation of the **abc** module. In Python 3.7, the **abc** module has both a C implementation as well as a Python one, but the Python implementation has a different file name that what **pylint** was expecting, resulting in some checks getting confused. - • Modules with **\_\_getattr\_\_** are exempted by default from **no-member** There's no easy way to figure out if a module has a particular member when the said module uses **\_\_getattr\_\_**, which is a new addition to Python 3.7. Instead we assume the safe thing to do, in the same way we do for classes, and skip those modules from checking. - • **invalid name** is no longer triggered for function and attribute names longer than 30 characters. The upper limit was removed completely. - • Fix false-positive **undefined-variable** for self referential class name in lamdbas - • **no-else-return** also specifies the type of the branch that is causing the error. - • Fixed inconsistent behaviour for bad-continuation on first line of file. - • Fixed a bug where **pylint** was not able to disable certain messages on the last line through the global disable option. - • **pylint** no longer emits **useless-return** when it finds a single statement that is the **return** itself We still want to be explicit when a function is supposed to return an optional value; even though **pass** could still work, it's not explicit enough and the function might look like it's missing an implementation. - • Fixed a bug where **pylint** was crashing when being unable to infer the value of an argument to **next()** - • **pylint** no longer emit **not-an-iterable** when dealing with async iterators. - • **pylint** gained the ability to specify a default docstring type for when the check cannot guess the type For this we added a **--default-docstring-type** command line option. ### Full changelog ### What's New in Pylint 2.1.1? Release date: 2018-08-07 - • fix pylint crash due to **misplaced-format-function** not correctly handling class attribute. Closes #2384 - • Do not emit \*-builtin for Python 3 builtin checks when the builtin is used inside a try-except Closes #2228 - • **simplifiable-if-statement** not emitted when dealing with subscripts ### What's New in Pylint 2.1? Release date: 2018-08-01 - • **trailing-comma-tuple** gets emitted for **yield** statements as well. Closes #2363 - • Get only the arguments of the scope function for **redefined-argument-from-local** Closes #2364 - • Add a check **misplaced-format-function** which is emitted if format function is used on non str object. Closes #2200 - • **chain.from\_iterable** no longer emits *dict-{}-not-iterating* when dealing with dict values and keys - • Demote the **try-except-raise** message from an error to a warning (E0705 -\> W0706) Closes #2323 - • Correctly handle the new name of the Python implementation of the **abc** module. Closes pylint-dev/astroid#2288 - • Modules with **\_\_getattr\_\_** are exempted by default from **no-member** There's no easy way to figure out if a module has a particular member when the said module uses **\_\_getattr\_\_**, which is a new addition to Python 3.7. Instead we assume the safe thing to do, in the same way we do for classes, and skip those modules from checking. Closes #2331 - • Fix a false positive **invalid name** message when method or attribute name is longer then 30 characters. Closes #2047 - • Include the type of the next branch in **no-else-return** Closes #2295 - • Fix inconsistent behaviour for bad-continuation on first line of file Closes #2281 - • Fix not being able to disable certain messages on the last line through the global disable option Closes #2278 - • Don't emit **useless-return** when we have a single statement that is the return itself We still want to be explicit when a function is supposed to return an optional value; even though **pass** could still work, it's not explicit enough and the function might look like it's missing an implementation. Closes #2300 - • Fix false-positive undefined-variable / E0602 \<#undefined-variable\> for self referential class name in lamdbas Closes #704 - • Don't crash when **pylint** is unable to infer the value of an argument to **next()** Closes #2316 - • Don't emit **not-an-iterable** when dealing with async iterators. But do emit it when using the usual iteration protocol against async iterators. Closes #2311 - • Can specify a default docstring type for when the check cannot guess the type Closes #1169 ### What's New In Pylint 2.0 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights - • Dropped support for Python 2. This release will work only on Python 3.4+. If you need to use **pylint** with Python 2, you can use Pylint 1.9+. We'll continue to do bug releases until 2020, when Python 2 goes officially EOL. **pylint** will gain the ability to analyze Python 2 files, but some checks might not work as they will assume that their running environment is Python 2. - • Given the dropping of Python 2, the Python 3 porting mode (enabled via **--py3k**) can now also run with Python 3. The porting mode used to be a no-op on Python 3, but most of the messages can now be emitted when the running interpreter is Python 3. The only messages that won't be emitted are those that rely on a particular syntax specific to Python 2, for instance **print** as a statement. ### New checkers - • A new check was added, **useless-object-inheritance**. This refactoring message is emitted when pylint detects that a class inherits from object, which is redundant as in Python 3, every class implicitly inherits from object. ``` class A(object): pass class A: # better pass ``` - • A new check was added, **comparison-with-callable**. This refactoring message is emitted when pylint detects that a comparison with a callable was made, which might suggest that some parenthesis were omitted, resulting in potential unwanted behaviour. ``` def foo(): return None def goo(): return None if foo == 786: # bad pass if foo() == 786: # good pass ``` - • A new check was added, **chained-comparison**. This refactoring message is emitted if a boolean operation can be simplified by chaining some of its operations. check below example: ``` if a < b and b < c: pass if a < b < c: # better pass ``` - • A new check was added, **useless-import-alias**. This refactoring message is emitted when an import alias does not rename the original package. ``` import numpy as numpy # bad import numpy as np # good from collection import OrderedDict as OrderedDict # bad from collection import OrderedDict as ordered_dict # good ``` - • A new check was added, **comparison-with-itself**. This refactoring message is emitted when a variable is compared against itself. ``` if variable == variable: # bad pass ``` - • A new check was added, **consider-using-in**. This refactoring message is emitted when a variable is compared against multiple values concatenated by ors instead of using the faster, more idiomatic "in" check. ``` if variable == 1 or variable == 2 or variable == 3: # bad pass if variable in (1, 2, 3): # good pass ``` - • A new check was added, **consider-using-get**. This refactoring message is emitted when manually checking if a key is in a dictionary and getting its value if it is (and optionally a default if not) instead of the more idiomatic dict.get. ``` if 'key' in dictionary: # bad variable = dictionary['key'] else: variable = 'default' variable = dictionary.get('key', 'default') # good ``` - • A new check was added, **consider-using-join**. This refactoring message is emitted when using a for loop over an iterable to join strings instead of the faster, less memory consuming and more idiomatic str.join(sequence). ``` result = '' # bad for number in ['1', '2', '3']: result += number result = ''.join(['1', '2', '3']) # good ``` - • New **useless-return** message when function or method ends with a "return" or "return None" statement and this is the only return statement in the body. - • New **use-symbolic-message-instead** message when a message is activated or deactivated by id instead of symbol. The use of symbol is more explicit and easier to remind. - • A new check was added, **consider-swap-variables**. This refactoring message is emitted when using a temporary variable in order to swap the values of two variables instead of the shorter, more idiomatic approach with tuple-unpacking. Instead of a temporary variable, the one-line syntax with commas should be used. See this style guide \ document or the Pycon 2007 *swap values presentation* for details. ``` temp = a # the wrong way a = b b = temp a, b = b, a # the right way ``` - • Two new checks, **invalid-envvar-value** and **invalid-envvar-default**, were added. The former is trigger whenever pylint detects that environment variable manipulation functions uses a different type than strings, while the latter is emitted whenever the said functions are using a default variable of different type than expected. - • A new check was added, **subprocess-popen-preexec-fn**, This refactoring message is emitted when using the keyword argument preexec\_fn when creating subprocess.Popen instances which may be unsafe when used in the presence of threads. See subprocess.Popen \ for full warning details. - • New **try-except-raise** message when an except handler block has a bare **raise** statement as its first operator or the exception type being raised is the same as the one being handled. - • New **possibly-unused-variable** check added. This is similar to **unused-variable**, the only difference is that it is emitted when we detect a locals() call in the scope of the unused variable. The **locals()** call could potentially use the said variable, by consuming all values that are present up to the point of the call. This new check allows to disable this error when the user intentionally uses **locals()** to consume everything. For instance, the following code will now trigger this new error: ``` def func(): some_value = some_call() return locals() ``` - • New **unhashable-dict-key** check added to detect dict lookups using unhashable keys such as lists or dicts. - • New **self-cls-assignment** warning check added. This is warning if the first argument of an instance/ class method gets assigned ``` class Foo(object): def foo(self, bar): self = bar ``` - • New verbose mode option **--verbose** to display of extra non-checker-related output. Disabled by default. - • Two new checks were added for recommending dict and set comprehensions where possible. These two checks are going to flag the following examples: ``` dict([(k, v) for (k, v) in ...]) # better as {k: v for k, v in ...} set([k for k in ...]) # better as {k for k in ...} ``` ### Other Changes - • A couple of performance improvements brought to **astroid** should make **pylint** should be a bit faster as well. We added a new flag, **max\_inferable\_values** on **astroid.MANAGER** for limiting the maximum amount of values that **astroid** can infer when inferring values. This change should improve the performance when dealing with large frameworks such as **django**. You can also control this behaviour with **pylint --limit-inference-results** We also rewrote how **nodes\_of\_class** and **get\_children** methods operate which should result in a performance boost for a couple of checks. - • Fix a false positive **inconsistent-return-statements** message when exception is raised inside an else statement. - • Don't warn for **missing-type-doc** and/or **missing-return-type-doc**, if type annotations exist on the function signature for a parameter and/or return type. - • Fix a false positive **inconsistent-return-statements** message when if statement is inside try/except. - • Fix a false positive **inconsistent-return-statements** message when **while** loop are used. - • Fix emission of false positive **no-member** message for class with "private" attributes whose name is mangled. - • Fix **unused-argument** false positives with overshadowed variable in dictionary comprehension. - • Fixing false positive **inconsistent-return-statements** when never returning functions are used (i.e such as sys.exit). - • Fix false positive **inconsistent-return-statements** message when a function is defined under an if statement. - • Fix false positive **inconsistent-return-statements** message by avoiding useless exception inference if the exception is not handled. - • Fix false positive **undefined-variable** for lambda argument in class definitions - • Suppress false-positive **not-callable** messages from certain staticmethod descriptors - • Expand **ignored-argument-names** include starred arguments and keyword arguments - • **singleton-comparison** will suggest better boolean conditions for negative conditions. - • **undefined-loop-variable** takes in consideration non-empty iterred objects before emitting. For instance, if the loop iterable is not empty, this check will no longer be emitted. - • Enum classes no longer trigger **too-few-methods** - • Special methods now count towards **too-few-methods**, and are considered part of the public API. They are still not counted towards the number of methods for **too-many-methods**. - • **docparams** extension allows abstract methods to document returns documentation even if the default implementation does not return something. They also no longer need to document raising a **NotImplementedError.** - • Skip wildcard import check for **\_\_init\_\_.py**. - • Don't warn useless-super-delegation / W0235 \<#useless-super-delegation\>' if the subclass method has different type annotations. - • Don't warn that a global variable is unused if it is defined by an import ``` def func(): global sys import sys ``` - • Added basic support for postponed evaluation of function annotations. If **pylint** detects the corresponding **from \_\_future\_\_ import annotations** import, it will not emit **used-before-assignment** and **undefined-variable** in the cases triggered by the annotations. More details on the postponed evaluation of annotations can be read in PEP 563 \. - • A new command line option was added, **--exit-zero**, for the use of continuous integration scripts which abort if a command returns a non-zero status code. If the option is specified, and Pylint runs successfully, it will exit with 0 regardless of the number of lint issues detected. Configuration errors, parse errors, and calling Pylint with invalid command-line options all still return a non-zero error code, even if **--exit-zero** is specified. - • Don't emit **unused-import** anymore for typing imports used in type comments. For instance, in the following example pylint used to complain that **Any** and **List** are not used, while they should be considered used by a type checker. ``` from typing import Any, List a = 1 # type: List[Any] ``` - • Fix false positive **line-too-long** for commented lines at the end of module - • Fix emitting **useless-super-delegation** when changing the default value of keyword arguments. - • Support **typing.TYPE\_CHECKING** for *:ref:\`unused-import\`* errors When modules are imported under **typing.TYPE\_CHECKING** guard, **pylint** will no longer emit *:ref:\`unused-import\`*. - • Fix false positive **unused-variable** in lambda default arguments - • **assignment-from-no-return** considers methods as well as functions. If you have a method that doesn't return a value, but later on you assign a value to a function call to that method (so basically it will be **None**), then **pylint** is going to emit an **assignment-from-no-return** error. - • A new flag was added, **--ignore-none** which controls the **no-member** behaviour with respect to **None** values. Previously **pylint** was not emitting **no-member** if it inferred that the owner of an attribute access is a **None** value. In some cases, this might actually cause bugs, so if you want to check for **None** values as well, pass **--ignore-none=n** to pylint. - • Fix false-positive **bad-continuation** for with statements - • Fix false-positive **bad-whitespace** message for typing annoatations with ellipses in them - • Fix false-positive **undefined-variable** for nested lambdas ### Full changelog ### What's New in Pylint 2.0? Release date: 2018-07-15 - • **try-except-raise** should not be emitted if there are any parent exception class handlers. Closes #2284 - • **trailing-comma-tuple** can be emitted for **return** statements as well. Closes #2269 - • Fix a false positive **inconsistent-return-statements** message when exception is raised inside an else statement. Closes #1782 - • **ImportFrom** nodes correctly use the full name for the import sorting checks. Closes #2181 - • \[\].extend and similar builtin operations don't emit *dict-\*-not-iterating* with the Python 3 porting checker Closes #2187 - • Add a check **consider-using-dict-comprehension** which is emitted if for dict initialization the old style with list comprehensions is used. - • Add a check **consider-using-set-comprehension** which is emitted if for set initialization the old style with list comprehensions is used. - • **logging-not-lazy** is emitted whenever pylint infers that a string is built with addition Closes #2193 - • Add a check **chained-comparison** which is emitted if a boolean operation can be simplified by chaining some of its operations. e.g "a \< b and b \< c", can be simplified as "a \< b \< c". Closes #2032 - • Add a check **consider-using-in** for comparisons of a variable against multiple values with "==" and "or"s instead of checking if the variable is contained "in" a tuple of those values. - • **in** is considered iterating context for some of the Python 3 porting checkers Closes #2186 - • Add **--ignore-none** flag to control if pylint should warn about **no-member** where the owner is None - • Fix a false positive related to **too-many-arguments** and bounded **\_\_get\_\_** methods Closes #2172 - • **mcs** as the first parameter of metaclass's **\_\_new\_\_** method was replaced by **cls** Closes #2028 - • **assignment-from-no-return** considers methods as well. Closes #2081 - • Support typing.TYPE\_CHECKING for *:ref:\`unused-import\`* errors Closes #1948 - • Inferred classes at a function level no longer emit **invalid-name** when they don't respect the variable regular expression Closes #1049 - • Added basic support for postponed evaluation of function annotations. Closes #2069 - • Fix a bug with **missing-kwoa** and variadics parameters Closes #1111 - • **simplifiable-if-statement** takes in account only when assigning to same targets Closes #1984 - • Make **len-as-condition** test more cases, such as **len() \< 1** or **len \<= 0** - • Fix false-positive **line-too-long** message emission for commented line at the end of a module Closes #1950 - • Fix false-positive **bad-continuation** for with statements Closes #461 - • Don't warn about **stop-iteration-return** when using **next()** over **itertools.count** Closes #2158 - • Add a check **consider-using-get** for unidiomatic usage of value/default-retrieval for a key from a dictionary Closes #2076 - • invalid-slice-index / E1127 \<#invalid-slice-index\> is not emitted when the slice is used as index for a complex object. We only use a handful of known objects (list, set and friends) to figure out if we should emit invalid-slice-index / E1127 \<#invalid-slice-index\> when the slice is used to subscript an object. - • Don't emit **unused-import** anymore for typing imports used in type comments. - • Add a new check useless-import-alias / C0414 \<#useless-import-alias\>'. Closes #2052 - • Add **comparison-with-callable** to warn for comparison with bare callable, without calling it. Closes #2082 - • Don't warn for **missing-type-doc** and/or **missing-return-type-doc**, if type annotations exist on the function signature for a parameter and/or return type. Closes #2083 - • Add **--exit-zero** option for continuous integration scripts to more easily call Pylint in environments that abort when a program returns a non-zero (error) status code. Closes #2042 - • Warn if the first argument of an instance/ class method gets assigned Closes #977 - • New check **comparison-with-itself** to check comparison between same value. Closes #2051 - • Add a new warning, logging-fstring-interpolation / W1203 \<#logging-fstring-interpolation\>', emitted when f-string is used within logging function calls. Closes #1998 - • Don't show useless-super-delegation / W0235 \<#useless-super-delegation\>' if the subclass method has different type annotations. Closes #1923 - • Add **unhashable-dict-key** check. Closes #586 - • Don't warn that a global variable is unused if it is defined by an import Closes #1453 - • Skip wildcard import check for **\_\_init\_\_.py**. Closes #2026 - • The Python 3 porting mode can now run with Python 3 as well. - • **too-few-public-methods** is not emitted for dataclasses. Closes #1793 - • New verbose mode option, enabled with **--verbose** command line flag, to display of extra non-checker-related output. It is disabled by default. Closes #1863 - • **undefined-loop-variable** takes in consideration non-empty iterred objects before emitting Closes #2039 - • Add support for numpydoc optional return value names. Closes #2030 - • **singleton-comparison** accounts for negative checks Closes #2037 - • Add a check **consider-using-in** for comparisons of a variable against multiple values with "==" and "or"s instead of checking if the variable is contained "in" a tuple of those values. Closes #1977 - • defaultdict and subclasses of dict are now handled for dict-iter-\* checks Closes #2005 - • **logging-format-interpolation** also emits when f-strings are used instead of % syntax. Closes #1788 - • Don't trigger misplaced-bare-raise / E0704 \<#misplaced-bare-raise\> when the raise is in a finally clause Closes #1924 - • Add a new check, **possibly-unused-variable**. This is similar to **unused-variable**, the only difference is that it is emitted when we detect a locals() call in the scope of the unused variable. The **locals()** call could potentially use the said variable, by consuming all values that are present up to the point of the call. This new check allows to disable this error when the user intentionally uses **locals()** to consume everything. Closes #1909. - • **no-else-return** accounts for multiple cases The check was a bit overrestrictive because we were checking for return nodes in the .orelse node. At that point though the if statement can be refactored to not have the orelse. This improves the detection of other cases, for instance it now detects TryExcept nodes that are part of the .else branch. Closes #1852 - • Added two new checks, **invalid-envvar-value** and **invalid-envvar-default**. The former is trigger whenever pylint detects that environment variable manipulation functions uses a different type than strings, while the latter is emitted whenever the said functions are using a default variable of different type than expected. - • Add a check **consider-using-join** for concatenation of strings using str.join(sequence) Closes #1952 - • Add a check **consider-swap-variables** for swapping variables with tuple unpacking Closes #1922 - • Add new checker **try-except-raise** that warns the user if an except handler block has a **raise** statement as its first operator. The warning is shown when there is a bare raise statement, effectively re-raising the exception that was caught or the type of the exception being raised is the same as the one being handled. - • Don't crash on invalid strings when checking for **logging-format-interpolation** Closes #1944 - • Exempt **\_\_doc\_\_** from triggering a **redefined-builtin** **\_\_doc\_\_** can be used to specify a docstring for a module without passing it as a first-statement string. - • Fix false positive bad-whitespace from function arguments with default values and annotations Closes #1831 - • Fix stop-iteration-return / R1708 \<#stop-iteration-return\> false positive when next builtin has a default value in a generator Closes #1830 - • Fix emission of false positive **no-member** message for class with "private" attributes whose name is mangled. Closes #1643 - • Fixed a crash which occurred when **Uninferable** wasn't properly handled in **stop-iteration-return** Closes #1779 - • Use the proper node to get the name for redefined functions (#1792) Closes #1774 - • Don't crash when encountering bare raises while checking inconsistent returns Closes #1773 - • Fix a false positive **inconsistent-return-statements** message when if statement is inside try/except. Closes #1770 - • Fix a false positive **inconsistent-return-statements** message when while loop are used. Closes #1772 - • Correct column number for whitespace conventions. Previously the column was stuck at 0 Closes #1649 - • Fix **unused-argument** false positives with overshadowed variable in dictionary comprehension. Closes #1731 - • Fix false positive **inconsistent-return-statements** message when never returning functions are used (i.e sys.exit for example). Closes #1771 - • Fix error when checking if function is exception, as in **bad-exception-context**. - • Fix false positive **inconsistent-return-statements** message when a function is defined under an if statement. Closes #1794 - • New **useless-return** message when function or method ends with a "return" or "return None" statement and this is the only return statement in the body. - • Fix false positive **inconsistent-return-statements** message by avoiding useless exception inference if the exception is not handled. Closes #1794 (second part) - • Fix bad thread instantiation check when target function is provided in args. Closes #1840 - • Fixed false positive when a numpy Attributes section follows a Parameters section Closes #1867 - • Fix incorrect file path when file absolute path contains multiple **path\_strip\_prefix** strings. Closes #1120 - • Fix false positive undefined-variable / E0602 \<#undefined-variable\> for lambda argument in class definitions Closes #1824 - • Add of a new checker that warns the user if some messages are enabled or disabled by id instead of symbol. Closes #1599 - • Suppress false-positive **not-callable** messages from certain staticmethod descriptors Closes #1699 - • Fix indentation handling with tabs Closes #1148 - • Fix false-positive **bad-continuation** error Closes #638 - • Fix false positive unused-variable / W0612 \<#unused-variable\> in lambda default arguments Closes #1921 Closes #1552 Closes #1099 Closes #210 - • Updated the default report format to include paths that can be clicked on in some terminals (e.g. iTerm). - • Fix inline def behavior with **too-many-statements** checker Closes #1978 - • Fix **KeyError** raised when using docparams and NotImplementedError is documented. Closes #2102 - • Fix method-hidden / E0202 \<#method-hidden\>' raised when assigning to a property or data descriptor. - • Fix emitting **useless-super-delegation** when changing the default value of keyword arguments. Closes #2022 - • Expand ignored-argument-names include starred arguments and keyword arguments Closes #2214 - • Fix false-positive undefined-variable / E0602 \<#undefined-variable\> in nested lambda Closes #760 - • Fix false-positive **bad-whitespace** message for typing annoatations with ellipses in them Close 1992 - • Broke down "missing-docstrings" between "module", "class" and "function" For this to work we had to make multiple messages with the same old name possible. Closes #1164 ### 1.x From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### What's New In Pylint 1.9 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights - • None so far ### New checkers - • A new Python 3 checker was added to warn about the removed **operator.div** function. - • A new Python 3 checker was added to warn about accessing functions that have been moved from the urllib module in corresponding subpackages, such as **urllib.request**. ``` from urllib import urlencode ``` Instead the previous code should use **urllib.parse** or **six.moves** to import a module in a Python 2 and 3 compatible fashion: ``` from six.moves.urllib.parse import urlencode ``` To have this working on Python 3 as well, please use the **six** library: ``` six.reraise(Exception, "value", tb) ``` - • A new check was added to warn about using unicode raw string literals. This is a syntax error in Python 3: ``` a = ur'...' ``` - • Added a new **deprecated-sys-function** check, emitted when accessing removed **sys** members. - • Added **xreadlines-attribute** check, emitted when the **xreadlines()** attribute is accessed on a file object. - • Added two new Python 3 porting checks, **exception-escape** and **comprehension-escape** These two are emitted whenever pylint detects that a variable defined in the said blocks is used outside of the given block. On Python 3 these values are deleted. ``` try: 1/0 except ZeroDivisionError as exc: ... print(exc) # This will raise a NameError on Python 3 [i for i in some_iterator if some_condition(i)] print(i) # This will raise a NameError on Python 3 ``` ### Other Changes - • **defaultdict** and subclasses of **dict** are now handled for *dict-iter-\** checks. That means that the following code will now emit warnings for when **iteritems** and friends are accessed: ``` some_dict = defaultdict(list) ... some_dict.iterkeys() ``` - • Enum classes no longer trigger **too-few-methods** - • Special methods now count towards **too-few-methods**, and are considered part of the public API. They are still not counted towards the number of methods for **too-many-methods**. - • docparams allows abstract methods to document returns documentation even if the default implementation does not return something. They also no longer need to document raising a NotImplementedError. ### Full changelog ### What's New in Pylint 1.9? Release date: 2018-05-15 - • Added two new Python 3 porting checks, **exception-escape** and **comprehension-escape** These two are emitted whenever pylint detects that a variable defined in the said blocks is used outside of the given block. On Python 3 these values are deleted. - • Added a new **deprecated-sys-function**, emitted when accessing removed sys members. - • Added **xreadlines-attribute**, emitted when the **xreadlines()** attribute is accessed. - • The Python 3 porting mode can now run with Python 3 as well. - • docparams extension allows abstract methods to document what overriding implementations should return, and to raise NotImplementedError without documenting it. Closes #2044 - • Special methods do not count towards **too-few-methods**, and are considered part of the public API. - • Enum classes do not trigger **too-few-methods** Closes #605 - • Added a new Python 2/3 check for accessing **operator.div**, which is removed in Python 3 Closes #1936 - • Added a new Python 2/3 check for accessing removed urllib functions Closes #1997 ### What's New In Pylint 1.8 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights - • None so far ### New checkers - • A new check was added, **shallow-copy-environ**. This warning message is emitted when shallow copy of os.environ is created. Shallow copy of os.environ doesn't work as people may expect. os.environ is not a dict object but rather a proxy object, so any changes made on copy may have unexpected effects on os.environ Instead of copy.copy(os.environ) method os.environ.copy() should be used. See \ for details. ``` import copy import os wrong_env_copy = copy.copy(os.environ) # will emit pylint warning wrong_env_copy['ENV_VAR'] = 'new_value' # changes os.environ assert os.environ['ENV_VAR'] == 'new_value' good_env_copy = dict(os.environ) # the right way good_env_copy['ENV_VAR'] = 'different_value' # doesn't change os.environ assert os.environ['ENV_VAR'] == 'new_value' ``` - • A new check was added, **keyword-arg-before-vararg**. This warning message is emitted when a function is defined with a keyword argument appearing before variable-length positional arguments (\*args). This may lead to args list getting modified if keyword argument's value is not provided in the function call assuming it will take default value provided in the definition. ``` def foo(a, b=3, *args): print(a, b, args) # Case1: a=0, b=2, args=(4,5) foo(0,2,4,5) # 0 2 (4,5) ==> Observed values are same as expected values # Case2: a=0, b=, args=(4,5) foo(0,4,5) # 0 4 (5,) ==> args list got modified as well as the observed value of b # Case3: Syntax Error if tried as follows foo(0,b=2,4,5) # syntax error ``` - • A new check was added, **simplify-boolean-expression**. This message is emitted when **consider-using-ternary** check would emit not equivalent code, due to truthy element being falsy in boolean context. ``` value = condition and False or other_value ``` This flawed construct may be simplified to: ``` value = other_value ``` - • A new check was added, **bad-thread-instantiation**. This message is emitted when the threading.Thread class does not receive the target argument, but receives just one argument, which is by default the group parameter. In the following example, the instantiation will fail, which is definitely not desired: ``` import threading threading.Thread(lambda: print(1)) # Oups, this is the group parameter ``` - • A new Python 3 checker was added to warn about accessing functions that have been removed from the itertools module **izip**, **imap**, **iflter**, **izip\_longest**, and **ifilterfalse**. ``` from itertools import izip print(list(izip([1, 2], [3]))) ``` Instead use **six.moves** to import a Python 2 and Python 3 compatible function: ``` from six.moves import zip print(list(zip([1, 2], [3]))) ``` - • A new Python 3 checker was added to warn about accessing deprecated fields from the types module like **ListType** or **IntType** ``` from types import ListType print(isinstance([], ListType)) ``` Instead use the declarations in the builtin namespace: ``` print(isinstance([], list)) ``` - • A new Python 3 checker was added to warn about declaring a **next** method that would have implemented the **Iterator** protocol in Python 2 but is now a normal method in Python 3. ``` class Foo(object): def next(self): return 42 ``` Instead implement a **\_\_next\_\_** method and use **six.Iterator** as a base class or alias **next** to **\_\_next\_\_**: ``` class Foo(object): def __next__(self): return 42 next = __next__ ``` - • Three new Python 3 checkers were added to warn about using dictionary methods in non-iterating contexts. For example, the following are returning iterators in Python 3: ``` .. code-block:: python ``` d = {} d.keys()\[0\] d.items()\[0\] d.values() + d.keys() - • A new Python 3 porting check was added, **non-ascii-bytes-literals** This message is emitted whenever we detect that a bytes string contain non-ASCII characters, which results in a SyntaxError on Python 3. - • A new warning, **raising-format-tuple**, will catch situations where the intent was likely raising an exception with a formatted message string, but the actual code did omit the formatting and instead passes template string and value parameters as separate arguments to the exception constructor. So it detects things like ``` raise SomeError('message about %s', foo) raise SomeError('message about {}', foo) ``` which likely were meant instead as ``` raise SomeError('message about %s' % foo) raise SomeError('message about {}'.format(foo)) ``` This warning can be ignored on projects which deliberately use lazy formatting of messages in all user-facing exception handlers. - • Following the recommendations of PEP479 \ ,a new Python 3.0 checker was added to warn about raising a **StopIteration** inside a generator. Raising a **StopIteration** inside a generator may be due a direct call to **raise StopIteration**: ``` def gen_stopiter(): yield 1 yield 2 yield 3 raise StopIteration ``` Instead use a simple **return** statement ``` def gen_stopiter(): yield 1 yield 2 yield 3 return ``` Raising a **StopIteration** may also be due to the call to **next** function with a generator as argument: ``` def gen_next_raises_stopiter(): g = gen_ok() while True: yield next(g) ``` In this case, surround the call to **next** with a try/except block: ``` def gen_next_raises_stopiter(): g = gen_ok() while True: try: yield next(g) except StopIteration: return ``` - • The check about raising a StopIteration inside a generator is also valid if the exception raised inherit from StopIteration. Closes #1385 - • A new Python checker was added to warn about using a **+** operator inside call of logging methods when one of the operands is a literal string: ``` import logging var = "123" logging.log(logging.INFO, "Var: " + var) ``` Instead use formatted string and positional arguments : ``` import logging var = "123" logging.log(logging.INFO, "Var: %s", var) ``` - • A new Python checker was added to warn about **inconsistent-return-statements**. A function or a method has inconsistent return statements if it returns both explicit and implicit values : ``` def mix_implicit_explicit_returns(arg): if arg < 10: return True elif arg < 20: return ``` According to PEP8 \, if any return statement returns an expression, any return statements where no value is returned should explicitly state this as return None, and an explicit return statement should be present at the end of the function (if reachable). Thus, the previous function should be written: ``` def mix_implicit_explicit_returns(arg): if arg < 10: return True elif arg < 20: return None ``` Closes #1267 ### Other Changes - • Fixing u'' string in superfluous-parens / C0325 \<#superfluous-parens\> message. - • Configuration options of invalid name checker are significantly redesigned. Predefined rules for common naming styles were introduced. For typical setups, user friendly options like **--function-naming-style=camelCase** may be used in place of hand-written regular expressions. Default linter config enforce PEP8-compatible naming style. See documentation for details. - • Raise meaningful exception in case of invalid reporter class (output format) being selected. - • The docparams extension now allows a property docstring to document both the property and the setter. Therefore setters can also have no docstring. - • The docparams extension now understands property type syntax. ``` class Foo(object): @property def foo(self): """My Sphinx style docstring description. :type: int """ return 10 ``` ``` class Foo(object): @property def foo(self): """int: My Numpy and Google docstring style description.""" return 10 ``` - • In case of **--output-format=json**, the dictionary returned holds a new key-value pair. The key is **message-id** and the value the message id. - • Spelling checker has a new configuration parameter **max-spelling-suggestions**, which affects maximum count of suggestions included in emitted message. - • The **:ref:\`invalid-name\`** check contains the name of the template that caused the failure. For the given code, **pylint** used to emit **invalid-name** in the form **Invalid constant name var**, without offering any context why **var** is not such a good name. With this change, it is now more clear what should be improved for a name to be accepted according to its corresponding template. - • New configuration flag, **suggestion-mode** was introduced. When enabled, pylint would attempt to emit user-friendly suggestions instead of spurious errors for some known false-positive scenarios. Flag is enabled by default. - • **superfluous-parens** is no longer wrongly emitted for logical statements involving **in** operator (see example below for what used to be false-positive). ``` foo = None if 'bar' in (foo or {}): pass ``` - • Redefinition of dummy function is now possible. **function-redefined** message won't be emitted anymore when dummy functions are redefined. - • **missing-param-doc** and **missing-type-doc** are no longer emitted when **Args** and **Keyword Args** are mixed in Google docstring. - • Fix of false positive **useless-super-delegation** message when parameters default values are different from those used in the base class. - • Fix of false positive **useless-else-on-loop** message when break statements are deeply nested inside loop. - • The Python 3 porting checker no longer emits multiple **no-absolute-import** per file. - • The Python 3 porting checker respects disabled checkers found in the config file. - • Modules, classes, or methods consist of compound statements that exceed the **docstring-min-length** are now correctly emitting **missing-docstring** - • Fix no **wrong-import-order** message emitted on ordering of first and third party libraries. With this fix, pylint distinguishes first and third party modules when checking import order. - • Fix the ignored **pylint disable=fixme** directives for comments following the last statement in a file. - • Fix **line-too-long** message deactivated by wrong disable directive. The directive **disable=fixme** doesn't deactivate anymore the emission of **line-too-long** message for long commented lines. - • If the rcfile specified on the command line doesn't exist, then an IOError exception is raised. - • Fix the wrong scope of **disable=** directive after a commented line. For example when a **disable=line-too-long** directive is at the end of a long commented line, it no longer disables the emission of **line-too-long** message for lines that follow. ### Full changelog ### What's New in Pylint 1.8.1? Release date: 2017-12-15 - • Wrong version number in \_\_pkginfo\_\_. ### What's New in Pylint 1.8? Release date: 2017-12-15 - • Respect disable=... in config file when running with --py3k. - • New warning **shallow-copy-environ** added Shallow copy of os.environ doesn't work as people may expect. os.environ is not a dict object but rather a proxy object, so any changes made on copy may have unexpected effects on os.environ Instead of copy.copy(os.environ) method os.environ.copy() should be used. See \ for details. Closes #1301 - • Do not display no-absolute-import warning multiple times per file. - • - **trailing-comma-tuple refactor check now extends to assignment with** more than one element (such as lists) Closes #1713 - • Fixing u'' string in superfluous-parens / C0325 \<#superfluous-parens\> message Closes #1420 - • **abstract-class-instantiated** is now emitted for all inference paths. Closes #1673 - • Add set of predefined naming style to ease configuration of checking naming conventions. Closes #1013 - • Added a new check, **keyword-arg-before-vararg** This is emitted for function definitions in which keyword arguments are placed before variable positional arguments (\*args). This may lead to args list getting modified if keyword argument's value is not provided in the function call assuming it will take default value provided in the definition. - • The **invalid-name** check contains the name of the template that caused the failure Closes #1176 - • Using the -j flag won't start more child linters than needed. Closes #1614 - • Fix a false positive with bad-python3-import on relative imports Closes #1608 - • Added a new Python 3 check, **non-ascii-bytes-literals** Closes #1545 - • Added a couple of new Python 3 checks for accessing dict methods in non-iterable context - • Protocol checks (not-a-mapping / E1134 \<#not-a-mapping\>, not-an-iterable / E1133 \<#not-an-iterable\> and co.) aren't emitted on classes with dynamic getattr - • Added a new warning, bad-thread-instantiation / W1506 \<#bad-thread-instantiation\>' This message is emitted when the threading.Thread class does not receive the target argument, but receives just one argument, which is by default the group parameter. Closes #1327 - • In non-quiet mode, absolute path of used config file is logged to standard error. Closes #1519 - • Raise meaningful exception for invalid reporter class being selected When unknown reporter class will be selected as Pylint reporter, meaningful error message would be raised instead of bare **ImportError** or **AttributeError** related to module or reporter class being not found. Closes #1388 - • Added a new Python 3 check for accessing removed functions from itertools like **izip** or **ifilterfalse** - • Added a new Python 3 check for accessing removed fields from the types module like **UnicodeType** or **XRangeType** - • Added a new Python 3 check for declaring a method **next** that would have been treated as an iterator in Python 2 but a normal function in Python 3. - • Added a new key-value pair in json output. The key is **message-id** and the value is the message id. Closes #1512 - • Added a new Python 3.0 check for raising a StopIteration inside a generator. The check about raising a StopIteration inside a generator is also valid if the exception raised inherit from StopIteration. Closes #1385 - • Added a new warning, **raising-format-tuple**, to detect multi-argument exception construction instead of message string formatting. - • Added a new check for method of logging module that concatenate string via + operator Closes #1479 - • Added parameter for limiting number of suggestions in spellchecking checkers - • Fix a corner-case in **consider-using-ternary** checker. When object **A** used in **X and A or B** was falsy in boolean context, Pylint incorrectly emitted non-equivalent ternary-based suggestion. After a change message is correctly not emitted for this case. Closes #1559 - • Added **suggestion-mode** configuration flag. When flag is enabled, informational message is emitted instead of cryptic error message for attributes accessed on c-extensions. Closes #1466 - • Fix a false positive **useless-super-delegation** message when parameters default values are different from those used in the base class. Closes #1085 - • Disabling wrong-import-order / C0411 \<#wrong-import-order\>', wrong-import-position / C0413 \<#wrong-import-position\>', or ungrouped-imports / C0412 \<#ungrouped-imports\>' for a single line now prevents that line from triggering violations on subsequent lines. Closes #1336 - • Added a new Python check for inconsistent return statements inside method or function. Closes #1267 - • Fix **superfluous-parens** false positive related to handling logical statements involving **in** operator. Closes #574 - • **function-redefined** message is no longer emitted for functions and methods which names matches dummy variable name regular expression. Closes #1369 - • Fix **missing-param-doc** and **missing-type-doc** false positives when mixing **Args** and **Keyword Args** in Google docstring. Closes #1409 - • Fix **missing-docstring** false negatives when modules, classes, or methods consist of compound statements that exceed the **docstring-min-length** - • Fix **useless-else-on-loop** false positives when break statements are deeply nested inside loop. Closes #1661 - • Fix no **wrong-import-order** message emitted on ordering of first and third party libraries. With this fix, pylint distinguishes third and first party modules when checking import order. Closes #1702 - • Fix **pylint disable=fixme** directives ignored for comments following the last statement in a file. Closes #1681 - • Fix **line-too-long** message deactivated by wrong disable directive. The directive **disable=fixme** doesn't deactivate anymore the emission of **line-too-long** message for long commented lines. Closes #1741 - • If the rcfile specified on the command line doesn't exist, then an IOError exception is raised. Closes #1747 - • Fix the wrong scope of the **disable=** directive after a commented line. For example when a **disable=line-too-long** directive is at the end of a long commented line, it no longer disables the emission of **line-too-long** message for lines that follow. Closes #1742 ### What's New In Pylint 1.7 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. ### Summary -- Release highlights ### New checkers - • **single-string-used-for-slots** check was added, which is used whenever a class is using a single string as a slot value. While this is technically not a problem per se, it might trip users when manipulating the slots value as an iterable, which would in turn iterate over characters of the slot value. In order to be more straight-forward, always try to use a container such as a list or a tuple for defining slot values. - • We added a new check, **literal-comparison**, which is used whenever **pylint** can detect a comparison to a literal. This is usually not what we want and, potentially, error prone. For instance, in the given example, the first string comparison returns true, since smaller strings are interned by the interpreter, while for larger ones, it will return False: ``` mystring = "ok" if mystring is "ok": # Returns true ... mystring = "a" * 1000 if mystring is ("a" * 1000): # This will return False ... ``` Instead of using the **is** operator, you should use the **==** operator for this use case. - • We added a new refactoring message, **consider-merging-isinstance**, which is emitted whenever we can detect that consecutive *isinstance* calls can be merged together. For instance, in this example, we can merge the first two *isinstance* calls: ``` # $ cat a.py if isinstance(x, int) or isinstance(x, float): pass if isinstance(x, (int, float)) or isinstance(x, str): pass # $ pylint a.py # R: 1, 0: Consider merging these isinstance calls to isinstance(x, (float, int)) (consider-merging-isinstance) # R: 3, 0: Consider merging these isinstance calls to isinstance(x, (int, float, str)) (consider-merging-isinstance) ``` - • A new error check was added, **invalid-metaclass**, which is used whenever *pylint* can detect that a given class is using a metaclass which is invalid for the purpose of the class. This usually might indicate a problem in the code, rather than something done on purpose. ``` # Needs to inherit from *type* in order to be valid class SomeClass(object): ... class MyClass(metaclass=SomeClass): pass ``` - • A new warning was added, **useless-super-delegation**, which is used whenever we can detect that an overridden method is useless, relying on *super()* delegation to do the same thing as another method from the MRO. For instance, in this example, the first two methods are useless, since they do the exact same thing as the methods from the base classes, while the next two methods are not, since they do some extra operations with the passed arguments. ``` class Impl(Base): def __init__(self, param1, param2): super(Impl, self).__init__(param1, param2) def useless(self, first, second): return super(Impl, self).useless(first, second) def not_useless(self, first, **kwargs): debug = kwargs.pop('debug', False) if debug: ... return super(Impl, self).not_useless(first, **kwargs) def not_useless_1(self, first, *args): return super(Impl, self).not_useless_1(first + some_value, *args) ``` - • A new warning was added, **len-as-condition**, which is used whenever we detect that a condition uses **len(SEQUENCE)** incorrectly. Instead one could use **if SEQUENCE** or **if not SEQUENCE**. For instance, all of the examples below: ``` if len(S): pass if not len(S): pass if len(S) > 0: pass if len(S) != 0: pass if len(S) == 0: pass ``` can be written in a more natural way: ``` if S: pass if not S: pass ``` See \ for more information. - • A new extension was added, **emptystring.py** which detects whenever we detect comparisons to empty string constants. This extension is disabled by default. For instance, the examples below: ``` if S != "": pass if S == '': pass ``` can be written in a more natural way: ``` if S: pass if not S: pass ``` An exception to this is when empty string is an allowed value whose meaning is treated differently than **None**. For example the meaning could be user selected no additional options vs. user has not made their selection yet! You can activate this checker by adding the line: ``` load-plugins=pylint.extensions.emptystring ``` to the **MAIN** section of your **.pylintrc** or using the command: ``` $ pylint a.py --load-plugins=pylint.extensions.emptystring ``` - • A new extension was added, **comparetozero.py** which detects whenever we compare integers to zero. This extension is disabled by default. For instance, the examples below: ``` if X != 0: pass if X == 0: pass ``` can be written in a more natural way: ``` if X: pass if not X: pass ``` An exception to this is when zero is an allowed value whose meaning is treated differently than **None**. For example the meaning could be **None** means no limit, while **0** means the limit it zero! You can activate this checker by adding the line: ``` load-plugins=pylint.extensions.comparetozero ``` to the **MAIN** section of your **.pylintrc** or using the command: ``` $ pylint a.py --load-plugins=pylint.extensions.comparetozero ``` - • We've added new error conditions for **bad-super-call** which now detect the usage of **super(type(self), self)** and **super(self.\_\_class\_\_, self)** patterns. These can lead to recursion loop in derived classes. The problem is visible only if you override a class that uses these incorrect invocations of **super()**. For instance, **Derived.\_\_init\_\_()** will correctly call **Base.\_\_init\_\_**. At this point **type(self)** will be equal to **Derived** and the call again goes to **Base.\_\_init\_\_** and we enter a recursion loop. ``` class Base(object): def __init__(self, param1, param2): super(type(self), self).__init__(param1, param2) class Derived(Base): def __init__(self, param1, param2): super(Derived, self).__init__(param1, param2) ``` - • The warnings **missing-returns-doc** and **missing-yields-doc** have each been replaced with two new warnings - **missing-\[return\|yield\]-doc** and **missing-\[return\|yield\]-type-doc**. Having these as separate warnings allows the user to choose whether their documentation style requires text descriptions of function return/yield, specification of return/yield types, or both. ``` # This will raise missing-return-type-doc but not missing-return-doc def my_sphinx_style_func(self): """This is a Sphinx-style docstring. :returns: Always False """ return False # This will raise missing-return-doc but not missing-return-type-doc def my_google_style_func(self): """This is a Google-style docstring. Returns: bool: """ return False ``` - • A new refactoring check was added, **redefined-argument-from-local**, which is emitted when **pylint** can detect than a function argument is redefined locally in some potential error prone cases. For instance, in the following piece of code, we have a bug, since the check will never return **True**, given the fact that we are comparing the same object to its attributes. ``` def test(resource): for resource in resources: # The ``for`` is reusing ``resource``, which means that the following # ``resource`` is not what we wanted to check against. if resource.resource_type == resource: call_resource(resource) ``` Other places where this check looks are *with* statement name bindings and except handler's name binding. - • A new refactoring check was added, **no-else-return**, which is emitted when pylint encounters an else following a chain of ifs, all of them containing a return statement. ``` def foo1(x, y, z): if x: return y else: # This is unnecessary here. return z ``` We could fix it deleting the **else** statement. ``` def foo1(x, y, z): if x: return y return z ``` - • A new Python 3 check was added, **eq-without-hash**, which enforces classes that implement **\_\_eq\_\_** *also* implement **\_\_hash\_\_**. The behavior around classes which implement **\_\_eq\_\_** but not **\_\_hash\_\_** changed in Python 3; in Python 2 such classes would get **object.\_\_hash\_\_** as their default implementation. In Python 3, aforementioned classes get **None** as their implementation thus making them unhashable. ``` class JustEq(object): def __init__(self, x): self.x = x def __eq__(self, other): return self.x == other.x class Neither(object): def __init__(self, x): self.x = x class HashAndEq(object): def __init__(self, x): self.x = x def __eq__(self, other): return self.x == other.x def __hash__(self): return hash(self.x) {Neither(1), Neither(2)} # OK in Python 2 and Python 3 {HashAndEq(1), HashAndEq(2)} # OK in Python 2 and Python 3 {JustEq(1), JustEq(2)} # Works in Python 2, throws in Python 3 ``` In general, this is a poor practice which motivated the behavior change. ``` as_set = {JustEq(1), JustEq(2)} print(JustEq(1) in as_set) # prints False print(JustEq(1) in list(as_set)) # prints True ``` In order to fix this error and avoid behavior differences between Python 2 and Python 3, classes should either explicitly set **\_\_hash\_\_** to **None** or implement a hashing function. ``` class JustEq(object): def __init__(self, x): self.x = x def __eq__(self, other): return self.x == other.x __hash__ = None {JustEq(1), JustEq(2)} # Now throws an exception in both Python 2 and Python 3. ``` - • 3 new Python 3 checkers were added, **div-method**, **idiv-method** and **rdiv-method**. The magic methods **\_\_div\_\_** and **\_\_idiv\_\_** have been phased out in Python 3 in favor of **\_\_truediv\_\_**. Classes implementing **\_\_div\_\_** that still need to be used from Python 2 code not using **from \_\_future\_\_ import division** should implement **\_\_truediv\_\_** and alias **\_\_div\_\_** to that implementation. ``` from __future__ import division class DivisibleThing(object): def __init__(self, x): self.x = x def __truediv__(self, other): return DivisibleThing(self.x / other.x) __div__ = __truediv__ ``` - • A new Python 3 checker was added to warn about accessing the **message** attribute on Exceptions. The message attribute was deprecated in Python 2.7 and was removed in Python 3. See \ for more information. ``` try: raise Exception("Oh No!!") except Exception as e: print(e.message) ``` Instead of relying on the **message** attribute, you should explicitly cast the exception to a string: ``` try: raise Exception("Oh No!!") except Exception as e: print(str(e)) ``` - • A new Python 3 checker was added to warn about using **encode** or **decode** on strings with non-text codecs. This check also checks calls to **open** with the keyword argument **encoding**. See \ for more information. ``` 'hello world'.encode('hex') ``` Instead of using the **encode** method for non-text codecs use the **codecs** module. ``` import codecs codecs.encode('hello world', 'hex') ``` - • A new warning was added, **overlapping-except**, which is emitted when an except handler treats two exceptions which are *overlapping*. This means that one exception is an ancestor of the other one or it is just an alias. For example, in Python 3.3+, IOError is an alias for OSError. In addition, socket.error is an alias for OSError. The intention is to find cases like the following: ``` import socket try: pass except (ConnectionError, IOError, OSError, socket.error): pass ``` - • A new Python 3 checker was added to warn about accessing **sys.maxint**. This attribute was removed in Python 3 in favor of **sys.maxsize**. ``` import sys print(sys.maxint) ``` Instead of using **sys.maxint**, use **sys.maxsize** ``` import sys print(sys.maxsize) ``` - • A new Python 3 checker was added to warn about importing modules that have either moved or been removed from the standard library. One of the major undertakings with Python 3 was a reorganization of the standard library to remove old or supplanted modules and reorganize some of the existing modules. As a result, roughly 100 modules that exist in Python 2 no longer exist in Python 3. See \ and \ for more information. There were suggestions on how to handle this, at pythonhosted.org/six/#module-six.moves (dead link) or python3porting.com/stdlib.html (dead link). ``` from cStringIO import StringIO ``` Instead of directly importing the deprecated module, either use **six.moves** or a conditional import. ``` from six.moves import cStringIO as StringIO if sys.version_info[0] >= 3: from io import StringIO else: from cStringIO import StringIO ``` This checker will assume any imports that happen within a conditional or a **try/except** block are valid. - • A new Python 3 checker was added to warn about accessing deprecated functions on the string module. Python 3 removed functions that were duplicated from the builtin **str** class. See \ for more information. ``` import string print(string.upper('hello world!')) ``` Instead of using **string.upper**, call the **upper** method directly on the string object. ``` "hello world!".upper() ``` - • A new Python 3 checker was added to warn about calling **str.translate** with the removed **deletechars** parameter. **str.translate** is frequently used as a way to remove characters from a string. ``` 'hello world'.translate(None, 'low') ``` Unfortunately, there is not an idiomatic way of writing this call in a 2and3 compatible way. If this code is not in the critical path for your application and the use of **translate** was a premature optimization, consider using **re.sub** instead: ``` import re chars_to_remove = re.compile('[low]') chars_to_remove.sub('', 'hello world') ``` If this code is in your critical path and must be as fast as possible, consider declaring a helper method that varies based upon Python version. ``` if six.PY3: def _remove_characters(text, deletechars): return text.translate({ord(x): None for x in deletechars}) else: def _remove_characters(text, deletechars): return text.translate(None, deletechars) ``` - • A new refactoring check was added, **consider-using-ternary**, which is emitted when pylint encounters constructs which were used to emulate ternary statement before it was introduced in Python 2.5. ``` value = condition and truth_value or false_value ``` Warning can be fixed by using standard ternary construct: ``` value = truth_value if condition else false_value ``` - • A new refactoring check was added, **trailing-comma-tuple**, which is emitted when pylint finds an one-element tuple, created by a stray comma. This can suggest a potential problem in the code and it is recommended to use parentheses in order to emphasise the creation of a tuple, rather than relying on the comma itself. The warning is emitted for such a construct: ``` a = 1, ``` The warning can be fixed by adding parentheses: ``` a = (1, ) ``` - • Two new check were added for detecting an unsupported operation over an instance, **unsupported-assignment-operation** and **unsupported-delete-operation**. The first one is emitted whenever an object does not support item assignment, while the second is emitted when an object does not support item deletion: ``` class A: pass instance = A() instance[4] = 4 # unsupported-assignment-operation del instance[4] # unsupported-delete-operation ``` - • A new check was added, **relative-beyond-top-level**, which is emitted when a relative import tries to access too many levels in the current package. - • A new check was added, **trailing-newlines**, which is emitted when a file has trailing new lines. - • **invalid-length-returned** check was added, which is emitted when a **\_\_len\_\_** implementation does not return a non-negative integer. - • There is a new extension, **pylint.extensions.mccabe**, which can be used for computing the McCabe complexity of classes and functions. You can enable this extension through **--load-plugins=pylint.extensions.mccabe** - • A new check was added, **used-prior-global-declaration**. This is emitted when a name is used prior a global declaration, resulting in a SyntaxError in Python 3.6. - • A new message was added, **assign-to-new-keyword**. This is emitted when used name is known to become a keyword in future Python release. Assignments to keywords would result in **SyntaxError** after switching to newer interpreter version. ``` # While it's correct in Python 2.x, it raises a SyntaxError in Python 3.x True = 1 False = 0 # Same as above, but it'll be a SyntaxError starting from Python 3.7 async = "async" await = "await" ``` ### Other Changes - • We don't emit by default **no-member** if we have opaque inference objects in the inference results This is controlled through the new flag **--ignore-on-opaque-inference**, which is by default True. The inference can return multiple potential results while evaluating a Python object, but some branches might not be evaluated, which results in partial inference. In that case, it might be useful to still emit no-member / E1101 \<#no-member\> and other checks for the rest of the inferred objects. - • Namespace packages are now supported by pylint. This includes both explicit namespace packages and implicit namespace packages, supported in Python 3 through PEP 420. - • A new option was added, **--analyse-fallback-block**. This can be used to support both Python 2 and 3 compatible import block code, which means that the import block might have code that exists only in one or another interpreter, leading to false positives when analysed. By default, this is false, you can enable the analysis for both branches using this flag. - • **ignored-argument-names** option is now used for ignoring arguments for unused-variable / W0612 \<#unused-variable\> check. This option was used for ignoring arguments when computing the correct number of arguments a function should have, but for handling the arguments with regard to unused-variable / W0612 \<#unused-variable\> check, dummy-variables-rgx was used instead. Now, ignored-argument-names is used for its original purpose and also for ignoring the matched arguments for the unused-variable / W0612 \<#unused-variable\> check. This offers a better control of what should be ignored and how. Also, the same option was moved from the design checker to the variables checker, which means that the option now appears under the **\[VARIABLES\]** section inside the configuration file. - • A new option was added, **redefining-builtins-modules**, for controlling the modules which can redefine builtins, such as six.moves and future.builtins. - • A new option was added, **ignore-patterns**, which is used for building a ignore list of directories and files matching the regex patterns, similar to the **ignore** option. - • The reports are now disabled by default, as well as the information category warnings. - • **arguments-differ** check was rewritten to take in consideration keyword only parameters and variadics. Now it also complains about losing or adding capabilities to a method, by introducing positional or keyword variadics. For instance, *pylint* now complains about these cases: ``` class Parent(object): def foo(self, first, second): ... def bar(self, **kwargs): ... def baz(self, *, first): ... class Child(Parent): # Why subclassing in the first place? def foo(self, *args, **kwargs): # mutate args or kwargs. super(Child, self).foo(*args, **kwargs) def bar(self, first=None, second=None, **kwargs): ... # The overridden method adds two new parameters, # which can also be passed as positional arguments, # breaking the contract of the parent's method. def baz(self, first): ... # Not keyword-only ``` - • **redefined-outer-name** is now also emitted when a nested loop's target variable is the same as an outer loop. ``` for i, j in [(1, 2), (3, 4)]: for j in range(i): print(j) ``` - • relax character limit for method and function names that starts with **\_**. This will let people to use longer descriptive names for methods and functions with a shorter scope (considered as private). The same idea applies to variable names, only with an inverse rule: you want long descriptive names for variables with bigger scope, like globals. - • Add **InvalidMessageError** exception class and replace **assert** in pylint.utils with **raise InvalidMessageError**. - • **UnknownMessageError** (formerly **UnknownMessage**) and **EmptyReportError** (formerly **EmptyReport**) are now provided by the new **pylint.exceptions** submodule instead of **pylint.utils** as before. - • We now support inline comments for comma separated values in the configurations For instance, you can now use the **#** sign for having comments inside comma separated values, as seen below: ``` disable=no-member, # Don't care about it for now bad-indentation, # No need for this import-error ``` Of course, interweaving comments with values is also working: ``` disable=no-member, # Don't care about it for now bad-indentation # No need for this ``` This works by setting the inline comment prefixes \ accordingly. - • Added epytext docstring support to the docparams extension. - • We added support for providing hints when not finding a missing member. For example, given the following code, it should be obvious that the programmer intended to use the **mail** attribute, rather than **email**. ``` class Contribution: def __init__(self, name, email, date): self.name = name self.mail = mail self.date = date for c in contributions: print(c.email) # Oups ``` **pylint** will now warn that there is a chance of having a typo, suggesting new names that could be used instead. ``` $ pylint a.py E: 8,10: Instance of 'Contribution' has no 'email' member; maybe 'mail'? ``` The behaviour is controlled through the **--missing-member-hint** option. Other options that come with this change are **--missing-member-max-choices** for choosing the total number of choices that should be picked in this situation and **--missing-member-hint-distance**, which specifies a metric for computing the distance between the names (this is based on Levenshtein distance, which means the lower the number, the more pickier the algorithm will be). - • **PyLinter.should\_analyze\_file** has a new parameter, **is\_argument**, which specifies if the given path is a **pylint** argument or not. **should\_analyze\_file** is called whenever **pylint** tries to determine if a file should be analyzed, defaulting to files with the **.py** extension, but this function gets called only in the case where the said file is not passed as a command line argument to **pylint**. This usually means that pylint will analyze a file, even if that file has a different extension, as long as the file was explicitly passed at command line. Since **should\_analyze\_file** cannot be overridden to handle all the cases, the check for the provenience of files was moved into **should\_analyze\_file**. This means we now can write something similar with this example, for ignoring every file respecting the desired property, disregarding the provenience of the file, being it a file passed as CLI argument or part of a package. ``` from pylint.lint import Run, PyLinter class CustomPyLinter(PyLinter): def should_analyze_file(self, modname, path, is_argument=False): if respect_condition(path): return False return super().should_analyze_file(modname, path, is_argument=is_argument) class CustomRun(Run): LinterClass = CustomPyLinter CustomRun(sys.argv[1:]) ``` - • Imports aliased with underscore are skipped when checking for unused imports. - • **bad-builtin** and **redefined-variable-type** are now extensions, being disabled by default. They can be enabled through: **--load-plugins=pylint.extensions.redefined\_variable\_type,pylint.extensions.bad\_builtin** - • Imports checker supports new switch **allow-wildcard-with-all** which disables warning on wildcard import when imported module defines **\_\_all\_\_** variable. - • **differing-param-doc** is now used for the differing part of the old **missing-param-doc**, and **differing-type-doc** for the differing part of the old **missing-type-doc**. ### Bug fixes - • Fix a false positive of **redundant-returns-doc**, occurred when the documented function was using *yield* instead of *return*. - • Fix a false positive of **missing-param-doc** and **missing-type-doc**, occurred when a class docstring uses the **For the parameters, see** magic string but the class **\_\_init\_\_** docstring does not, or vice versa. - • Added proper exception type inference for **missing-raises-doc**. Now: ``` def my_func(): """"My function.""" ex = ValueError('foo') raise ex ``` will properly be flagged for missing documentation of **:raises ValueError:** instead of **:raises ex:**, among other scenarios. - • Fix false positives of **missing-\[raises\|params\|type\]-doc** due to not recognizing valid keyword synonyms supported by Sphinx. - • More thorough validation in **MessagesStore.register\_messages()** to detect conflicts between a new message and any existing message id, symbol, or **old\_names**. - • We now support having plugins that shares the same name and with each one providing options. A plugin can be logically split into multiple classes, each class providing certain capabilities, all of them being tied under the same name. But when two or more such classes are also adding options, then **pylint** crashed, since it already added the first encountered section. Now, these should work as expected. ``` from pylint.checkers import BaseChecker class DummyPlugin1(BaseChecker): name = 'dummy_plugin' msgs = {'I9061': ('Dummy short desc 01', 'dummy-message-01', 'Dummy long desc')} options = ( ('dummy_option_1', { 'type': 'string', 'metavar': '', 'help': 'Dummy option 1', }), ) class DummyPlugin2(BaseChecker): name = 'dummy_plugin' msgs = {'I9060': ('Dummy short desc 02', 'dummy-message-02', 'Dummy long desc')} options = ( ('dummy_option_2', { 'type': 'string', 'metavar': '', 'help': 'Dummy option 2', }), ) def register(linter): linter.register_checker(DummyPlugin1(linter)) linter.register_checker(DummyPlugin2(linter)) ``` - • We do not yield **unused-argument** for singledispatch implementations and do not warn about **function-redefined** for multiple implementations with same name. ``` from functools import singledispatch @singledispatch def f(x): return 2*x @f.register(str) def _(x): return -1 @f.register(int) @f.register(float) def _(x): return -x ``` - • **unused-variable** checker has new functionality of warning about unused variables in global module namespace. Since globals in module namespace may be a part of exposed API, this check is disabled by default. For enabling it, set **allow-global-unused-variables** option to false. - • Fix a false-positive **logging-format-interpolation** message, when format specifications are used in formatted string. In general, these operations are not always convertible to old-style formatting used by logging module. - • Added a new switch **single-line-class-stmt** to allow single-line declaration of empty class bodies (as seen in the example below). Pylint won't emit a **multiple-statements** message when this option is enabled. ``` class MyError(Exception): pass ``` - • **too-many-format-args** and **too-few-format-args** are emitted correctly (or not emitted at all, when exact count of elements in RHS cannot be inferred) when starred expressions are used in RHS tuple. For example, code block as shown below detects correctly that the used tuple has in fact three elements, not two. ``` meat = ['spam', 'ham'] print('%s%s%s' % ('eggs', *meat)) ``` - • **cyclic-import** checker supports local disable clauses. When one of cycle imports was done in scope where disable clause was active, cycle is not reported as violation. ### Removed Changes - • **pylint-gui** was removed, because it was deemed unfit for being included in *pylint*. It had a couple of bugs and misfeatures, its usability was subpar and since its development was neglected, we decided it is best to move on without it. - • The HTML reporter was removed, including the **--output-format=html** option. It was lately a second class citizen in Pylint, being mostly neglected. Since we now have the JSON reporter, it can be used as a basis for building more prettier HTML reports than what Pylint can currently generate. This is part of the effort of removing cruft from Pylint, by removing less used features. - • The **--files-output** option was removed. While the same functionality cannot be easily replicated, the JSON reporter, for instance, can be used as a basis for generating the messages per each file. - • **--required-attributes** option was removed. - • **--ignore-iface-methods** option was removed. - • The **--optimize-ast** flag was removed. The option was initially added for handling pathological cases, such as joining too many strings using the addition operator, which was leading pylint to have a recursion error when trying to figure out what the string was. Unfortunately, we decided to ignore the issue, since the pathological case would have happen when the code was parsed by Python as well, without actually reaching the runtime step and as such, we decided to remove the error altogether. - • **epylint.py\_run**'s *script* parameter was removed. Now **epylint.py\_run** is always using the underlying **epylint.lint** method from the current interpreter. This avoids some issues when multiple instances of **pylint** are installed, which means that **epylint.py\_run** might have ran a different **epylint** script than what was intended. ### Full changelog ### What's New in Pylint 1.7.1? Release date: 2017-04-17 - • Fix a false positive which occurred when an exception was reraised Closes #1419 - • Fix a false positive of **disallow-trailing-tuple** The check was improved by verifying for non-terminating newlines, which should exempt function calls and function definitions from the check Closes #1424 ### What's New in Pylint 1.7? Release date: 2017-04-13 - • Don't emit missing-final-newline / C0304 \<#missing-final-newline\> or trailing-whitespace / C0303 \<#trailing-whitespace\> for formfeeds (page breaks). Closes #1218 and #1219 - • Don't emit by default no-member / E1101 \<#no-member\> if we have opaque inference objects in the inference results This is controlled through the new flag ignore-on-opaque-inference, which is by default True. The inference can return multiple potential results while evaluating a Python object, but some branches might not be evaluated, which results in partial inference. In that case, it might be useful to still emit no-member / E1101 \<#no-member\> and other checks for the rest of the inferred objects. - • Added new message **assign-to-new-keyword** to warn about assigning to names which will become a keyword in future Python releases. Closes #1351 - • Split the 'missing or differing' in parameter documentation in different error. differing-param-doc / W9017 \<#differing-param-doc\> covers the differing part of the old missing-param-doc / W9015 \<#missing-param-doc\>', and differing-type-doc / W9018 \<#differing-type-doc\>' covers the differing part of the old missing-type-doc / W9016 \<#missing-type-doc\>' Closes #1342 - • Added a new error, used-prior-global-declaration / E0118 \<#used-prior-global-declaration\>', which is emitted when a name is used prior a global declaration in a function. This causes a SyntaxError in Python 3.6 Closes #1257 - • The protocol checks are emitting their messages when a special method is set to None. Closes #1263 - • Properly detect if imported name is assigned to same name in different scope. Closes #636, #848, #851, and #900 - • Require one space for annotations with type hints, as per PEP 8. - • trailing-comma-tuple / R1707 \<#trailing-comma-tuple\>' check was added This message is emitted when pylint finds an one-element tuple, created by a stray comma. This can suggest a potential problem in the code and it is recommended to use parentheses in order to emphasise the creation of a tuple, rather than relying on the comma itself. - • Don't emit not-callable / E1102 \<#not-callable\> for instances with unknown bases. Closes #1213 - • Treat keyword only arguments the same as positional arguments with regard to unused-argument / W0613 \<#unused-argument\> check - • Don't try to access variables defined in a separate scope when checking for **protected-access** - • Added new check to detect incorrect usage of len(SEQUENCE) inside test conditions. - • Added new extension to detect comparisons against empty string constants - • Added new extension to detect comparisons of integers against zero - • Added new error conditions for bad-super-call / E1003 \<#bad-super-call\>' Now detects **super(type(self), self)** and **super(self.\_\_class\_\_, self)** which can lead to recursion loop in derived classes. - • PyLinter.should\_analyze\_file has a new optional parameter, called **is\_argument** Closes #1079 - • Add attribute hints for missing members Closes #1035 - • Add a new warning, redefined-argument-from-local / R1704 \<#redefined-argument-from-local\>' Closes #649 - • Support inline comments for comma separated values in the config file Closes #1024 - • epylint.py\_run's *script* parameter was removed. - • epylint.py\_run now uses **shell=False** for running the underlying process. Closes #441 - • Added a new warning, useless-super-delegation / W0235 \<#useless-super-delegation\>' Close 839. - • Added a new error, invalid-metaclass / E1139 \<#invalid-metaclass\>', raised when we can detect that a class is using an improper metaclass. Closes #579 - • Added a new refactoring message, literal-comparison / R0123 \<#literal-comparison\>'. Closes #786 - • arguments-differ / W0221 \<#arguments-differ\> takes in consideration kwonlyargs and variadics Closes #983 - • Removed --optimized-ast Fixes part of #975 - • Removed --files-output option Fixes part of #975 - • Removed pylint-gui from the package. - • Removed the HTML reporter Fixes part of #975 - • ignored-argument-names is now used for ignoring arguments for unused-variable / W0612 \<#unused-variable\> check. This option was used for ignoring arguments when computing the correct number of arguments a function should have, but for handling the arguments with regard to unused-variable / W0612 \<#unused-variable\> check, dummy-variables-rgx was used instead. Now, ignored-argument-names is used for its original purpose and also for ignoring the matched arguments for the unused-variable / W0612 \<#unused-variable\> check. This offers a better control of what should be ignored and how. Also, the same option was moved from the design checker to the variables checker, which means that the option now appears under the **\[VARIABLES\]** section inside the configuration file. Closes #862. - • Fix a false positive for keyword variadics with regard to keyword only arguments. If a keyword only argument was necessary for a function, but that function was called with keyword variadics (\*\*kwargs), then we were emitting a missing-kwoa / E1125 \<#missing-kwoa\> false positive, which is now fixed. Closes #934. - • Fix some false positives with unknown sized variadics. Closes #878 - • Added a new extension, check\_docstring, for checking PEP 257 conventions. Closes #868. - • config files with BOM markers can now be read. Closes #864. - • epylint.py\_run does not crash on big files, using .communicate() instead of .wait() Closes #599 - • Disable reports by default and show the evaluation score by default The reports were disabled by default in order to simplify the interaction between the tool and the users. The score is still shown by default, as a way of closely measuring when it increases or decreases due to changes brought to the code. Refs #746 - • Disable the information category messages by default. This is a step towards making pylint more sane. Refs #746. - • Catch more cases as not proper iterables for \_\_slots\_\_ with regard to invalid-slots / E0238 \<#invalid-slots\> pattern. Closes #775 - • empty indent strings are rejected. - • Added a new error, relative-beyond-top-level / E0402 \<#relative-beyond-top-level\>', which is emitted when a relative import was attempted beyond the top level package. Closes #588 - • Added a new warning, unsupported-assignment-operation / E1137 \<#unsupported-assignment-operation\>', which is emitted when item assignment is tried on an object which doesn't have this ability. Closes #591 - • Added a new warning, unsupported-delete-operation / E1138 \<#unsupported-delete-operation\>', which is emitted when item deletion is tried on an object which doesn't have this ability. Closes #592 - • Fix a false positive of redundant-returns-doc / W9008 \<#redundant-returns-doc\>', occurred when the documented function was using *yield* instead of *return*. Closes #984. - • Fix false positives of 'missing-\[raises\|params\|type\]-doc' due to not recognizing keyword synonyms supported by Sphinx. - • Added a new refactoring message, consider-merging-isinstance / R1701 \<#consider-merging-isinstance\>', which is emitted whenever we can detect that consecutive isinstance calls can be merged together. Closes #968 - • Fix a false positive of missing-param-doc / W9015 \<#missing-param-doc\>' and missing-type-doc / W9016 \<#missing-type-doc\>', occurred when a class docstring uses the 'For the parameters, see' magic string but the class \_\_init\_\_ docstring does not, or vice versa. - • **redefined-outer-name** is now also emitted when a nested loop's target variable is the same as a target variable in an outer loop. Closes #911. - • Added proper exception type inference for missing-raises-doc / W9006 \<#missing-raises-doc\>'. - • Added InvalidMessageError exception class to replace asserts in pylint.utils. - • More thorough validation in MessagesStore.register\_messages() to avoid one message accidentally overwriting another. - • InvalidMessageError, UnknownMessage, and EmptyReport exceptions are moved to the new pylint.exceptions submodule. - • UnknownMessage and EmptyReport are renamed to UnknownMessageError and EmptyReportError. - • Warnings 'missing-returns-type-doc' and 'missing-yields-type-doc' have each been split into two warnings - 'missing-\[return\|yield\]-doc' and 'missing-\[return\|yield\]-type-doc'. - • Added epytext support to docparams extension. Closes #1029 - • Support having plugins with the same name and with options defined Closes #1018 - • Sort configuration options in a section Closes #1087 - • Added a new Python 3 warning around implementing '\_\_div\_\_', '\_\_idiv\_\_', or '\_\_rdiv\_\_' as those methods are phased out in Python 3. - • Added a new warning, overlapping-except / W0714 \<#overlapping-except\>', which is emitted when two exceptions in the same except-clause are aliases for each other or one exceptions is an ancestor of another. - • Avoid crashing on ill-formatted strings when checking for string formatting errors. - • Added a new Python 3 warning for calling 'str.encode' or 'str.decode' with a non-text encoding. - • Added new coding convention message, single-string-used-for-slots / C0205 \<#single-string-used-for-slots\>'. Closes #1166 - • Added a new Python 3 check for accessing 'sys.maxint' which was removed in Python 3 in favor of 'sys.maxsize' - • Added a new Python 3 check for bad imports. - • Added a new Python 3 check for accessing deprecated string functions. - • Do not warn about unused arguments or function being redefined in singledispatch registered implementations. Closes #1032 and #1034 - • Added refactoring message no-else-return / R1705 \<#no-else-return\>'. - • Improve unused-variable / W0612 \<#unused-variable\> checker to warn about unused variables in module scope. Closes #919 - • Ignore modules import as \_ when checking for unused imports. Closes #1190 - • Improve handing of Python 3 classes with metaclasses declared in nested scopes. Closes #1177 - • Added refactoring message consider-using-ternary / R1706 \<#consider-using-ternary\>'. Closes #1204 - • Bug-fix for false-positive logging-format-interpolation\` when format specifications are used in formatted string. Closes #572 - • Added a new switch **single-line-class-stmt** to allow single-line declaration of empty class bodies. Closes #738 - • Protected access in form **type(self).\_attribute** are now allowed. Closes #1031 - • Let the user modify msg-template when Pylint is called from a Python script Closes #1269 - • Imports checker supports new switch **allow-wildcard-with-all** which disables warning on wildcard import when imported module defines **\_\_all\_\_** variable. Closes #831 - • **too-many-format-args** and **too-few-format-args** are emitted correctly when starred expression are used in RHS tuple. Closes #957 - • **cyclic-import** checker supports local disable clauses. When one of cycle imports was done in scope where disable clause was active, cycle is not reported as violation. Closes #59 ### What's New In Pylint 1.6 From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. From pylint 1.6.0 to 2.14.0, on top of the full changelog there was also a summary of (mostly user facing) changes. Ticket numbers can be internal to logilab or come from bitbucket. ### Summary -- Release highlights Nothing major. ### New checkers - • We added a new recommendation check, **consider-iterating-dictionary**, which is emitted when a dictionary is iterated by using **.keys()**. For instance, the following code would trigger this warning, since the dictionary's keys can be iterated without calling the method explicitly. ``` for key in dictionary.keys(): ... # Can be refactored to: for key in dictionary: ... ``` - • **trailing-newlines** check was added, which is emitted when a file has trailing newlines. - • **invalid-length-returned** check was added, which is emitted when the **\_\_len\_\_** special method returns something else than a non-negative number. For instance, this example is triggering it: ``` class Container(object): def __len__(self): return self._items # Oups, forgot to call len() over it. ``` - • Add a new check to the *check\_docs* extension for looking for duplicate constructor parameters in a class constructor docstring or in a class docstring. The check **multiple-constructor-doc** is emitted when the parameter is documented in both places. - • We added a new extension plugin, **pylint.extensions.mccabe**, which can be used for warning about the complexity in the code. You can enable it as in: ``` $ pylint module_or_project --load-plugins=pylint.extensions.mccabe ``` See more at Design checker \<#pylint-extensions-mccabe\> ### New features - • **generated-members** now supports qualified names through regular expressions. For instance, for ignoring all the errors generated by **numpy.core**'s attributes, we can now use: ``` $ pylint a.py --generated-members=numpy.* ``` - • Add the ability to ignore files based on regex matching, with the new **--ignore-patterns** option. Rather than clobber the existing **ignore** option, we decided to have a separate option for it. For instance, for ignoring all the test files, we can now use: ``` $ pylint myproject --ignore-patterns=test.*?py ``` - • We added a new option, **redefining-builtins-modules**, which is used for defining the modules which can redefine builtins. *pylint* will emit an error when a builtin is redefined, such as defining a variable called **next**. But in some cases, the builtins can be redefined in the case they are imported from other places, different than the **builtins** module, such is the case for **six.moves**, which contains more forward-looking functions: ``` $ cat a.py # Oups, now pylint emits a redefined-builtin message. from six.moves import open $ pylint a.py --redefining-builtins-modules=six.moves ``` Default values: **six.moves,future.builtins** ### Bug fixes - • Fixed a bug where the top name of a qualified import was detected as an unused variable. - • We don't warn about **invalid-sequence-index** if the indexed object has unknown base classes, that Pylint cannot deduce. ### Other Changes - • The **bad-builtin** check was moved into an extension. The check was complaining about used builtin functions which were supposed to not be used. For instance, **map** and **filter** were falling into this category, since better alternatives can be used, such as list comprehensions. But the check was annoying, since using **map** or **filter** can have its use cases and as such, we decided to move it to an extension check instead. It can now be enabled through **--load-plugins=pylint.extensions.bad\_builtin**. - • We use the **configparser** backport internally, for Python 2. This allows having comments inside list values, in the configuration, such as: ``` disable=no-member, # Don't like this check bad-indentation ``` - • We now use the isort \ package internally. This improves the **\`wrong-import-order** check, so now we should have less false positives regarding the import order. - • We do not emit **import-error** or **no-name-in-module** for fallback import blocks by default. A fallback import block can be considered a TryExcept block, which contains imports in both branches, such as: ``` try: import urllib.request as request except ImportError: import urllib2 as request ``` In the case where **pylint** can not find one import from the **except** branch, then it will emit an **import-error**, but this gets cumbersome when trying to write compatible code for both Python versions. As such, we don't check these blocks by default, but the analysis can be enforced by using the new **--analyse-fallback-block** flag. - • **reimported** is emitted when the same name is imported from different module, as in: ``` from collections import deque, OrderedDict, deque ``` ### Deprecated features - • The HTML support was deprecated and will be eventually removed in Pylint 1.7.0. This feature was lately a second class citizen in Pylint, being often neglected and having a couple of bugs. Since we now have the JSON reporter, this can be used as a basis for more prettier HTML outputs than what Pylint can currently offer. - • The **--files-output** option was deprecated and will be eventually removed in Pylint 1.7.0. - • The **--optimize-ast** option was deprecated and will be eventually removed in Pylint 1.7.0. The option was initially added for handling pathological cases, such as joining too many strings using the addition operator, which was leading pylint to have a recursion error when trying to figure out what the string was. Unfortunately, we decided to ignore the issue, since the pathological case would have happen when the code was parsed by Python as well, without actually reaching the runtime step and as such, we will remove the option in the future. - • The **check\_docs** extension is now deprecated. The extension is still available under the **docparams** name, so this should work: ``` $ pylint module_or_package --load-extensions=pylint.extensions.docparams ``` The old name is still kept for backward compatibility, but it will be eventually removed. ### Removed features - • None yet ### Full changelog ### What's new in Pylint 1.6.3? Release date: 2016-07-18 - • Do not crash when inferring uninferable exception types for docparams extension Closes #998 ### What's new in Pylint 1.6.2? Release date: 2016-07-15 - • Do not crash when printing the help of options with default regular expressions Closes #990 - • More granular versions for deprecated modules. Closes #991 ### What's new in Pylint 1.6.1? Release date: 2016-07-07 - • Use environment markers for supporting conditional dependencies. ### What's New in Pylint 1.6.0? Release date: 2016-07-03 - • Added a new extension, **pylint.extensions.mccabe**, for warning about complexity in code. - • Deprecate support for --optimize-ast Fixes part of #975 - • Deprecate support for the HTML output Fixes part of #975 - • Deprecate support for --output-files Fixes part of #975 - • Fixed a documentation error for the check\_docs extension. Closes #735 - • Made the list of property-defining decorators configurable. - • Fix a bug where the top name of a qualified import was detected as unused variable. Closes #923 - • bad-builtin / W0141 \<#bad-builtin\> is now an extension check. - • generated-members support qualified name through regular expressions. For instance, one can specify a regular expression as --generated-members=astroid.node\_classes.\* for ignoring every no-member / E1101 \<#no-member\> error that is accessed as in **astroid.node\_classes.missing.object**. - • Add the ability to ignore files based on regex matching, with the new **--ignore-patterns** option. Allow for multiple ignore patterns to be specified. Rather than clobber the existing ignore option, we introduced a new one called ignore-patterns. Closes #156 - • Added a new error, trailing-newlines / C0305 \<#trailing-newlines\>, which is emitted when a file has trailing new lines. Closes #682 - • Add a new option, 'redefining-builtins-modules', for controlling the modules which can redefine builtins, such as six.moves and future.builtins. Closes #464 - • 'reimported' is emitted when the same name is imported from different module. Closes #162 - • Add a new recommendation checker, consider-iterating-dictionary / C0201 \<#consider-iterating-dictionary\>, which is emitted which is emitted when a dictionary is iterated through .keys(). Closes #699 - • Use the configparser backport for Python 2 This fixes a problem we were having with comments inside values, which is fixed in Python 3's configparser. Closes #828 - • A new error was added, invalid-length-returned / E0303 \<#invalid-length-returned\>, when the **\_\_len\_\_** special method returned something else than a non-negative number. Closes #557 - • Switch to using isort internally for wrong-import-order / C0411 \<#wrong-import-order\>. Closes #879 - • check\_docs extension can find constructor parameters in \_\_init\_\_. Closes #887 - • Don't warn about invalid-sequence-index / E1126 \<#invalid-sequence-index\> if the indexed object has unknown base classes. Closes #867 - • Don't crash when checking, for super-init-not-called / W0231 \<#super-init-not-called\>, a method defined in an if block. - • Do not emit import-error / E0401 \<#import-error\> or no-name-in-module / E0611 \<#no-name-in-module\> for fallback import blocks by default. Until now, we warned with these errors when a fallback import block (a TryExcept block that contained imports for Python 2 and 3) was found, but this gets cumbersome when trying to write compatible code. As such, we don't check these blocks by default, but the analysis can be enforced by using the new **--analyse-fallback-block** flag. Closes #769. Ticket numbers are almost can be internal to Logilab, or from bitbucket. In latest version it's also github issues. ### What's New In Pylint 1.5 ### What's New in Pylint 1.5.5? Release date: 2016-03-21 - • Let visit\_importfrom from Python 3 porting checker be called when everything is disabled Because the visit method was filtering the patterns it was expecting to be activated, it didn't run when everything but one pattern was disabled, leading to spurious false positives Closes #852 - • Don't emit unsubscriptable-value for classes with unknown base classes. Closes #776. - • Use an OrderedDict for storing the configuration elements This fixes an issue related to impredictible order of the disable / enable elements from a config file. In certain cases, the disable was coming before the enable which resulted in classes of errors to be enabled, even though the intention was to disable them. The best example for this was in the context of running multiple processes, each one of it having different enables / disables that affected the output. Closes #815 - • Don't consider bare and broad except handlers as ignoring NameError, AttributeError and similar exceptions, in the context of checkers for these issues. Closes #826 ### What's New in Pylint 1.5.4? Release date: 2016-01-15 - • Merge StringMethodChecker with StringFormatChecker. This fixes a bug where disabling all the messages and enabling only a handful of messages from the StringFormatChecker would have resulted in no messages at all. - • Don't apply unneeded-not / C0113 \<#unneeded-not\> over sets. ### What's New in Pylint 1.5.3? Release date: 2016-01-11 - • Handle the import fallback idiom with regard to wrong-import-order / C0411 \<#wrong-import-order\>. Closes #750 - • Decouple the displaying of reports from the displaying of messages Some reporters are aggregating the messages instead of displaying them when they are available. The actual displaying was conflatted in the generate\_reports. Unfortunately this behaviour was flaky and in the case of the JSON reporter, the messages weren't shown at all if a file had syntax errors or if it was missing. In order to fix this, the aggregated messages can now be displayed with Reporter.display\_message, while the reports are displayed with display\_reports. Closes #766 Closes #765 - • Ignore function calls with variadic arguments without a context. Inferring variadic positional arguments and keyword arguments will result into empty Tuples and Dicts, which can lead in some cases to false positives with regard to no-value-for-parameter / E1120 \<#no-value-for-parameter\>. In order to avoid this, until we'll have support for call context propagation, we're ignoring such cases if detected. Closes #722 - • Treat AsyncFunctionDef just like FunctionDef nodes, by implementing visit\_asyncfunctiondef in terms of visit\_functiondef. Closes #767 - • Take in account kwonlyargs when verifying that arguments are defined with the check\_docs extension. Closes #745 - • Suppress reporting unneeded-not / C0113 \<#unneeded-not\> inside **\_\_ne\_\_** methods Closes #749 ### What's New in Pylint 1.5.2? Release date: 2015-12-21 - • Don't crash if graphviz is not installed, instead emit a warning letting the user to know. Closes #168 - • Accept only functions and methods for the deprecated-method / W4902 \<#deprecated-method\> checker. This prevents a crash which can occur when an object doesn't have .qname() method after the inference. - • Don't emit super-on-old-class on classes with unknown bases. Closes #721 - • Allow statements in **if** or **try** blocks containing imports. Closes #714 ### What's New in Pylint 1.5.1? Release date: 2015-12-02 - • Fix a crash which occurred when old visit methods are encountered in plugin modules. Closes #711 - • Add wrong-import-position / C0413 \<#wrong-import-position\> to check\_messages's decorator arguments for ImportChecker.leave\_module This fixes an esoteric bug which occurs when ungrouped-imports / C0412 \<#ungrouped-imports\> and wrong-import-order / C0411 \<#wrong-import-order\> are disabled and pylint is executed on multiple files. What happens is that without wrong-import-position / C0413 \<#wrong-import-position\> in check\_messages, leave\_module will never be called, which means that the first non-import node from other files might leak into the current file, leading to wrong-import-position / C0413 \<#wrong-import-position\> being emitted by pylint. - • Fix a crash which occurred when old visit methods are encountered in plugin modules. Closes #711 - • Don't emit import-self / W0406 \<#import-self\> and cyclic-import / R0401 \<#cyclic-import\> for relative imports of modules with the same name as the package itself. Closes #708 Closes #706. ### What's New in Pylint 1.5.0? Release date: 2015-11-29 - • Added multiple warnings related to imports. wrong-import-order / C0411 \<#wrong-import-order\> is emitted when PEP 8 recommendations regarding imports are not respected (that is, standard imports should be followed by third-party imports and then by local imports). ungrouped-imports / C0412 \<#ungrouped-imports\> is emitted when imports from the same package or module are not placed together, but scattered around in the code. wrong-import-position / C0413 \<#wrong-import-position\> is emitted when code is mixed with imports, being recommended for the latter to be at the top of the file, in order to figure out easier by a human reader what dependencies a module has. Closes #692 - • Added a new refactoring warning, unneeded-not / C0113 \<#unneeded-not\>, emitted when an expression with the not operator could be simplified. Closes #670 - • Added a new refactoring warning, simplifiable-if-statement / R1703 \<#simplifiable-if-statement\>, used when an if statement could be reduced to a boolean evaluation of its test. Closes #698 - • Added a new refactoring warning, too-many-boolean-expressions / R0916 \<#too-many-boolean-expressions\>, used when an if statement contains too many boolean expressions, which makes the code less maintainable and harder to understand. Closes #677 - • Property methods are shown as attributes instead of functions in pyreverse class diagrams. Closes #284 - • Add a new refactoring error, too-many-nested-blocks / R1702 \<#too-many-nested-blocks\>, which is emitted when a function or a method has too many nested blocks, which makes the code less readable and harder to understand. Closes #668 - • Add a new error, unsubscriptable-object / E1136 \<#unsubscriptable-object\>, that is emitted when value used in subscription expression doesn't support subscription (i.e. doesn't define \_\_getitem\_\_ method). - • Don't warn about abstract classes instantiated in their own body. Closes #627 - • Obsolete options are not present by default in the generated configuration file. Closes #632 - • non-iterator-returned / E0301 \<#non-iterator-returned\> can detect classes with iterator-metaclasses. Closes #679 - • Add a new error, unsupported-membership-test / E1135 \<#unsupported-membership-test\>, emitted when value to the right of the 'in' operator doesn't support membership test protocol (i.e. doesn't define \_\_contains\_\_/\_\_iter\_\_/\_\_getitem\_\_) - • Add new errors, not-an-iterable / E1133 \<#not-an-iterable\>, emitted when non-iterable value is used in an iterating context (starargs, for-statement, comprehensions, etc), and not-a-mapping / E1134 \<#not-a-mapping\>, emitted when non-mapping value is used in a mapping context. Closes #563 - • Make no-self-use / R6301 \<#no-self-use\> checker not emit a warning if there is a 'super()' call inside the method. Closes #667 - • Add checker to identify multiple imports on one line. Closes #598 - • Fix unused-argument / W0613 \<#unused-argument\> false positive when the "+=" operator is used. Closes #518 - • Don't emit import-error / E0401 \<#import-error\> for ignored modules. PyLint will not emit import errors for any import which is, or is a subpackage of, a module in the ignored-modules list. Closes #223 - • Fix unused-import / W0611 \<#unused-import\> false positive when the import is used in a class assignment. Closes #475 - • Add a new error, not-context-manager / E1129 \<#not-context-manager\>, emitted when something that doesn't implement \_\_enter\_\_ and \_\_exit\_\_ is used in a with statement. - • Add a new warning, confusing-with-statement / W0124 \<#confusing-with-statement\>, emitted by the base checker, when an ambiguous looking with statement is used. For example *with open() as first, second* which looks like a tuple assignment but is actually 2 context managers. - • Add a new warning, duplicate-except / W0705 \<#duplicate-except\>, emitted when there is an exception handler which handles an exception type that was handled before. Closes #485 - • A couple of warnings got promoted to errors, since they could uncover potential bugs in the code. These warnings are: assignment-from-none / E1128 \<#assignment-from-none\>, unbalanced-tuple-unpacking / W0632 \<#unbalanced-tuple-unpacking\>, unpacking-non-sequence / E0633 \<#unpacking-non-sequence\>, non-iterator-returned / E0301 \<#non-iterator-returned\>. Closes #388 - • Allow ending a pragma control with a semicolon. In this way, users can continue a pragma control with a reason for why it is used, as in *# pylint: disable=old-style-class;reason=...*. Closes #449 - • \--jobs can be used with --load-plugins now. Closes #456 - • Improve the performance of --jobs when dealing only with a package name. Closes #479 - • Don't emit an unused-wildcard-import / W0614 \<#unused-wildcard-import\> when the imported name comes from another module and it is in fact a \_\_future\_\_ name. - • The colorized reporter now works on Windows. Closes #96. - • Remove pointless-except warning. It was previously disabled by default and it wasn't very useful. Closes #506. - • Fix a crash on Python 3 related to the string checker, which crashed when it encountered a bytes string with a .format method called. - • Don't warn about no-self-use / R6301 \<#no-self-use\> for builtin properties. - • Fix a false positive for bad-reversed-sequence / E0111 \<#bad-reversed-sequence\>, when a subclass of a **dict** provides a \_\_reversed\_\_ method. - • Change the default no-docstring-rgx so missing-docstring / C0111 \<#missing-docstring\> isn't emitted for private functions. - • Don't emit redefined-outer-name / W0621 \<#redefined-outer-name\> for \_\_future\_\_ directives. Closes #520. - • Provide some hints for the bad-builtin / W0141 \<#bad-builtin\> message. Closes #522. - • When checking for invalid arguments to a callable, in typecheck.py, look up for the \_\_init\_\_ in case the found \_\_new\_\_ comes from builtins. Since the \_\_new\_\_ comes from builtins, it will not have attached any information regarding what parameters it expects, so the check will be useless. Retrieving \_\_init\_\_ in that case will at least detect a couple of false negatives. Closes #429. - • Don't emit no-member / E1101 \<#no-member\> for classes with unknown bases. Since we don't know what those bases might add, we simply ignore the error in this case. - • Lookup in the implicit metaclass when checking for no-member / E1101 \<#no-member\>, if the class in question has an implicit metaclass, which is True for new style classes. Closes #438. - • Add two new warnings, duplicate-bases / E0241 \<#duplicate-bases\> and inconsistent-mro / E0240 \<#inconsistent-mro\>. duplicate-bases / E0241 \<#duplicate-bases\> is emitted when a class has the same bases listed more than once in its bases definition, while inconsistent-mro / E0240 \<#inconsistent-mro\> is emitted when no sane mro hierarchy can be determined. Closes #526. - • Remove interface-not-implemented warning. Closes #532. - • Remove the rest of interface checks: interface-is-not-class, missing-interface-method, unresolved-interface. The reason is that it's better to start recommending ABCs instead of the old Zope era of interfaces. One side effect of this change is that ignore-iface-methods becomes a noop, it's deprecated and it will be removed at some time. - • Emit a proper deprecation warning for reporters.BaseReporter.add\_message. The alternative way is to use handle\_message. add\_message will be removed in Pylint 1.6. - • Added new module 'extensions' for optional checkers with the test directory 'test/extensions' and documentation file 'doc/extensions.rst'. - • Added new checker 'extensions.check\_docs' that verifies parameter documentation in Sphinx, Google, and Numpy style. - • Detect undefined variable cases, where the "definition" of an undefined variable was in del statement. Instead of emitting used-before-assignment / E0601 \<#used-before-assignment\>, which is totally misleading, it now emits undefined-variable / E0602 \<#undefined-variable\>. Closes #528. - • Don't emit attribute-defined-outside-init / W0201 \<#attribute-defined-outside-init\> and access-member-before-definition / E0203 \<#access-member-before-definition\> for mixin classes. Actual errors can occur in mixin classes, but this is controlled by the ignore-mixin-members option. Closes #412. - • Improve the detection of undefined variables and variables used before assignment for variables used as default arguments to function, where the variable was first defined in the class scope. Closes #342 and issue #404. - • Add a new warning, unexpected-special-method-signature / E0302 \<#unexpected-special-method-signature\>, which is emitted when a special method (dunder method) doesn't have the expected signature, which can lead to actual errors in the application code. Closes #253. - • Remove bad-context-manager / E0235 \<#bad-context-manager\> due to the inclusion of unexpected-special-method-signature / E0302 \<#unexpected-special-method-signature\>. - • Don't emit no-name-in-module / E0611 \<#no-name-in-module\> if the import is guarded by an ImportError, Exception or a bare except clause. - • Don't emit no-member / E1101 \<#no-member\> if the attribute access node is protected by an except handler, which handles AttributeError, Exception or it is a bare except. - • Don't emit import-error / E0401 \<#import-error\> if the import is guarded by an ImportError, Exception or a bare except clause. - • Don't emit undefined-variable / E0602 \<#undefined-variable\> if the node is guarded by a NameError, Exception or bare except clause. - • Add a new warning, using-constant-test / W0125 \<#using-constant-test\>, which is emitted when a conditional statement (If, IfExp) uses a test which is always constant, such as numbers, classes, functions etc. This is most likely an error from the user's part. Closes #524. - • Don't emit raising-non-exception / E0710 \<#raising-non-exception\> when the exception has unknown bases. We don't know what those bases actually are and it's better to assume that the user knows what he is doing rather than emitting a message which can be considered a false positive. - • Look for a .pylintrc configuration file in the current folder, if pylintrc is not found. Dotted pylintrc files will not be searched in the parents of the current folder, as it is done for pylintrc. - • Add a new error, 'invalid-unary-type-operand', emitted when an unary operand is used on something which doesn't support that operation (for instance, using the unary bitwise inversion operator on an instance which doesn't implement \_\_invert\_\_). - • Take in consideration differences between arguments of various type of functions (classmethods, staticmethods, properties) when checking for **arguments-differ**. Closes #548. - • astroid.inspector was moved to pylint.pyreverse, since it belongs there and it doesn't need to be in astroid. - • astroid.utils.LocalsVisitor was moved to pylint.pyreverse.LocalsVisitor. - • pylint.checkers.utils.excepts\_import\_error was removed. Use pylint.checkers.utils.error\_of\_type instead. - • Don't emit undefined-all-variables for nodes which can't be inferred (YES nodes). - • yield-outside-func is also emitted for **yield from**. - • Add a new error, too-many-star-expressions / E0112 \<#too-many-star-expressions\>, emitted when there are more than one starred expression (*\*x*) in an assignment. The warning is emitted only on Python 3. - • Add a new error, invalid-star-assignment-target / E0113 \<#invalid-star-assignment-target\>, emitted when a starred expression (*\*x*) is used as the lhs side of an assignment, as in *\*x = \[1, 2\]*. This is not a SyntaxError on Python 3 though. - • Detect a couple of objects which can't be base classes (bool, slice, range and memoryview, which weren't detected until now). - • Add a new error for the Python 3 porting checker, **import-star-module-level**, which is used when a star import is detected in another scope than the module level, which is an error on Python 3. Using this will emit a SyntaxWarning on Python 2. - • Add a new error, star-needs-assignment-target / E0114 \<#star-needs-assignment-target\>, emitted on Python 3 when a Starred expression (*\*x*) is not used in an assignment target. This is not caught when parsing the AST on Python 3, so it needs to be a separate check. - • Add a new error, unsupported-binary-operation / E1131 \<#unsupported-binary-operation\>, emitted when two a binary arithmetic operation is executed between two objects which don't support it (a number plus a string for instance). This is currently disabled, since the it exhibits way too many false positives, but it will be re-enabled as soon as possible. - • New imported features from astroid into pyreverse: pyreverse.inspector.Project, pyreverse.inspector.project\_from\_files and pyreverse.inspector.interfaces. These were moved since they didn't belong in astroid. - • Enable misplaced-future / W0410 \<#misplaced-future\> for Python 3. Closes #580. - • Add a new error, nonlocal-and-global / E0115 \<#nonlocal-and-global\>, which is emitted when a name is found to be both nonlocal and global in the same scope. Closes #581. - • ignored-classes option can work with qualified names (ignored-classes=optparse.Values) Closes #297 - • ignored-modules can work with qualified names as well as with Unix pattern matching for recursive ignoring. Closes #244 - • Improve detection of relative imports in non-packages, as well as importing missing modules with a relative import from a package. - • Don't emit no-init if not all the bases from a class are known. Closes #604. - • \--no-space-check option accepts **empty-line** as a possible option. Closes #541. - • \--generate-rcfile generates by default human readable symbols for the --disable option. Closes #608. - • Improved the not-in-loop / E0103 \<#not-in-loop\> checker to properly detect more cases. - • Add a new error, continue-in-finally / W0136 \<#continue-in-finally\>, which is emitted when the **continue** keyword is found inside a **finally** clause, which is a SyntaxError. - • The --zope flag is deprecated and it is slated for removal in Pylint 1.6. The reason behind this removal is the fact that it's a specialized flag and there are solutions for the original problem: use --generated-members with the members that causes problems when using Zope or add AST transforms tailored to the zope project. At the same time, --include-ids and --symbols will also be removed in Pylint 1.6. Closes #570. - • missing-module-attribute was removed and the corresponding CLI option, required-attributes, which is slated for removal in Pylint 1.6. - • missing-reversed-argument was removed. The reason behind this is that this kind of errors should be detected by the type checker for *all* the builtins and not as a special case for the reversed builtin. This will happen shortly in the future. - • \--comment flag is obsolete and it will be removed in Pylint 1.6. - • \--profile flag is obsolete and it will be removed in Pylint 1.6. - • Add a new error, misplaced-bare-raise / E0704 \<#misplaced-bare-raise\>. The error is used when a bare raise is not used inside an except clause. This can generate a RuntimeError in Python, if there are no active exceptions to be reraised. While it works in Python 2 due to the fact that the exception leaks outside of the except block, it's nevertheless a behaviour that a user shouldn't depend upon, since it's not obvious to the reader of the code what exception will be raised and it will not be compatible with Python 3 anyhow. Closes #633. - • Bring logilab-common's ureports into pylint.reporters. With this change, we moved away from depending on logilab-common, having in Pylint all the components that were used from logilab-common. The API should be considered an implementation detail and can change at some point in the future. Closes #621. - • **reimported** is emitted for reimported objects on the same line. Closes #639. - • Abbreviations of command line options are not supported anymore. Using abbreviations for CLI options was never considered to be a feature of pylint, this fact being only a side effect of using optparse. As this was the case, using --load-plugin or other abbreviation for --load-plugins never actually worked, while it also didn't raise an error. Closes #424. - • Add a new error, nonlocal-without-binding / E0117 \<#nonlocal-without-binding\> The error is emitted on Python 3 when a nonlocal name is not bound to any variable in the parents scopes. Closes #582. - • - **deprecated-module / W4901 \<#deprecated-module\> can be shown for modules which aren't** available. Closes #362. - • Don't consider a class abstract if its members can't be properly inferred. This fixes a false positive related to abstract-class-instantiated / E0110 \<#abstract-class-instantiated\>. Closes #648. - • Add a new checker for the async features added by PEP 492. - • Add a new error, yield-inside-async-function / E1700 \<#yield-inside-async-function\>, emitted on Python 3.5 and upwards when the **yield** statement is found inside a new coroutine function (PEP 492). - • Add a new error, not-async-context-manager / E1701 \<#not-async-context-manager\>, emitted when an async context manager block is used with an object which doesn't support this protocol (PEP 492). - • Add a new convention warning, singleton-comparison / C0121 \<#singleton-comparison\>, emitted when comparison to True, False or None is found. - • Don't emit assigning-non-slot / E0237 \<#assigning-non-slot\> for descriptors. Closes #652. - • Add a new error, repeated-keyword / E1132 \<#repeated-keyword\>, when a keyword argument is passed multiple times into a function call. This is similar with redundant-keyword-arg / E1124 \<#redundant-keyword-arg\>, but it's mildly different that it needs to be a separate error. - • \--enable=all can now be used. Closes #142. - • Add a new convention message, misplaced-comparison-constant / C2201 \<#misplaced-comparison-constant\>, emitted when a constant is placed in the left hand side of a comparison, as in '5 == func()'. This is also called Yoda condition, since the flow of code reminds of the Star Wars green character, conditions usually encountered in languages with variabile assignments in conditional statements. - • Add a new convention message, consider-using-enumerate / C0200 \<#consider-using-enumerate\>, which is emitted when code that uses **range** and **len** for iterating is encountered. Closes #684. - • Added two new refactoring messages, no-classmethod-decorator / R0202 \<#no-classmethod-decorator\> and no-staticmethod-decorator / R0203 \<#no-staticmethod-decorator\>, which are emitted when a static method or a class method is declared without using decorators syntax. Closes #675. ### What's New In Pylint 1.4 ### What's New in Pylint 1.4.3? Release date: 2015-03-14 - • Remove three warnings: star-args, abstract-class-little-used, abstract-class-not-used. These warnings don't add any real value and they don't imply errors or problems in the code. - • Added a new option for controlling the peephole optimizer in astroid. The option **--optimize-ast** will control the peephole optimizer, which is used to optimize a couple of AST subtrees. The current problem solved by the peephole optimizer is when multiple joined strings, with the addition operator, are encountered. If the numbers of such strings is high enough, Pylint will then fail with a maximum recursion depth exceeded error, due to its visitor architecture. The peephole just transforms such calls, if it can, into the final resulting string and this exhibit a problem, because the visit\_binop method stops being called (in the optimized AST it will be a Const node). ### What's New in Pylint 1.4.2? Release date: 2015-03-11 - • Don't require a docstring for empty modules. Closes #261 - • Fix a false positive with **too-few-format-args** string warning, emitted when the string format contained a normal positional argument ('{0}'), mixed with a positional argument which did an attribute access ('{0.\_\_class\_\_}'). Closes #463 - • Take in account all the methods from the ancestors when checking for too-few-public-methods / R0903 \<#too-few-public-methods\>. Closes #471 - • Catch enchant errors and emit invalid-characters-in-docstring / C0403 \<#invalid-characters-in-docstring\> when checking for spelling errors. Closes #469 - • Use all the inferred statements for the super-init-not-called / W0231 \<#super-init-not-called\> check. Closes #389 - • Add a new warning, 'unichr-builtin', emitted by the Python 3 porting checker, when the unichr builtin is found. Closes #472 - • Add a new warning, 'intern-builtin', emitted by the Python 3 porting checker, when the intern builtin is found. Closes #473 - • Add support for editable installations. - • The HTML output accepts the **--msg-template** option. Patch by Dan Goldsmith. - • Add 'map-builtin-not-iterating' (replacing 'implicit-map-evaluation'), 'zip-builtin-not-iterating', 'range-builtin-not-iterating', and 'filter-builtin-not-iterating' which are emitted by **--py3k** when the appropriate built-in is not used in an iterating context (semantics taken from 2to3). - • Add a new warning, unidiomatic-typecheck / C0123 \<#unidiomatic-typecheck\>, emitted when an explicit typecheck uses type() instead of isinstance(). For example, *type(x) == Y* instead of *isinstance(x, Y)*. Patch by Chris Rebert. Closes #299 - • Add support for combining the Python 3 checker mode with the --jobs flag (--py3k and --jobs). Closes #467 - • Add a new warning for the Python 3 porting checker, 'using-cmp-argument', emitted when the **cmp** argument for the **list.sort** or **sorted builtin** is encountered. - • Make the --py3k flag commutative with the -E flag. Also, this patch fixes the leaks of error messages from the Python 3 checker when the errors mode was activated. Closes #437 ### What's New in Pylint 1.4.1? Release date: 2015-01-16 - • Look only in the current function's scope for bad-super-call / E1003 \<#bad-super-call\>. Closes #403 - • Check the return of properties when checking for not-callable / E1102 \<#not-callable\>. Closes #406 - • Warn about using the input() or round() built-ins for Python 3. Closes #411 - • Proper abstract method lookup while checking for abstract-class-instantiated / E0110 \<#abstract-class-instantiated\>. Closes #401 - • Use a mro traversal for finding abstract methods. Closes #415 - • Fix a false positive with catching-non-exception / E0712 \<#catching-non-exception\> and tuples of exceptions. - • Fix a false negative with raising-non-exception / E0710 \<#raising-non-exception\>, when the raise used an uninferrable exception context. - • Fix a false positive on Python 2 for raising-bad-type / E0702 \<#raising-bad-type\>, when raising tuples in the form 'raise (ZeroDivisionError, None)'. - • Fix a false positive with invalid-slots-objects, where the slot entry was a unicode string on Python 2. Closes #421 - • Add a new warning, redundant-unittest-assert / W1503 \<#redundant-unittest-assert\>, emitted when using unittest's methods assertTrue and assertFalse with constant value as argument. Patch by Vlad Temian. - • Add a new JSON reporter, usable through -f flag. - • Add the method names for the signature-differs / W0222 \<#signature-differs\> and 'argument-differs' warnings. Closes #433 - • Don't compile test files when installing. - • Fix a crash which occurred when using multiple jobs and the files given as argument didn't exist at all. ### What's New in Pylint 1.4.0? Release date: 2014-11-23 - • Added new options for controlling the loading of C extensions. By default, only C extensions from the stdlib will be loaded into the active Python interpreter for inspection, because they can run arbitrary code on import. The option **--extension-pkg-whitelist** can be used to specify modules or packages that are safe to load. - • Change default max-line-length to 100 rather than 80 - • Drop BaseRawChecker class which were only there for backward compatibility for a while now - • Don't try to analyze string formatting with objects coming from function arguments. Closes #373 - • Port source code to be Python 2/3 compatible. This drops the need for 2to3, but does drop support for Python 2.5. - • Each message now comes with a confidence level attached, and can be filtered base on this level. This allows to filter out all messages that were emitted even though an inference failure happened during checking. - • Improved presenting unused-import / W0611 \<#unused-import\> message. Closes #293 - • Add new checker for finding spelling errors. New messages: wrong-spelling-in-comment / C0401 \<#wrong-spelling-in-comment\>, wrong-spelling-in-docstring / C0402 \<#wrong-spelling-in-docstring\>. New options: spelling-dict, spelling-ignore-words. - • Add new '-j' option for running checks in sub-processes. - • Added new checks for line endings if they are mixed (LF vs CRLF) or if they are not as expected. New messages: mixed-line-endings / C0327 \<#mixed-line-endings\>, unexpected-line-ending-format / C0328 \<#unexpected-line-ending-format\>. New option: expected-line-ending-format. - • dangerous-default-value / W0102 \<#dangerous-default-value\> no longer evaluates the value of the arguments, which could result in long error messages or sensitive data being leaked. Closes #282 - • Fix a false positive with string formatting checker, when encountering a string which uses only position-based arguments. Closes #285 - • Fix a false positive with string formatting checker, when using keyword argument packing. Closes #288 - • Proper handle class level scope for lambdas. - • Handle too-few-format-args / E1306 \<#too-few-format-args\> or too-many-format-args / E1305 \<#too-many-format-args\> for format strings with both named and positional fields. Closes #286 - • Analyze only strings by the string format checker. Closes #287 - • Properly handle nested format string fields. Closes #294 - • Don't emit attribute-defined-outside-init / W0201 \<#attribute-defined-outside-init\> if the attribute was set by a function call in a defining method. Closes #192 - • Properly handle unicode format strings for Python 2. Closes #296 - • Don't emit import-error / E0401 \<#import-error\> if an import was protected by a try-except, which excepted ImportError. - • Fix an unused-import / W0611 \<#unused-import\> false positive, when the error was emitted for all the members imported with 'from import' form. Closes #304 - • Don't emit invalid-name / C0103 \<#invalid-name\> when assigning a name in an ImportError handler. Closes #302 - • Don't count branches from nested functions. - • Fix a false positive with too-few-format-args / E1306 \<#too-few-format-args\>, when the format strings contains duplicate manual position arguments. Closes #310 - • fixme regex handles comments without spaces after the hash. Closes #311 - • Don't emit unused-import / W0611 \<#unused-import\> when a special object is imported (\_\_all\_\_, \_\_doc\_\_ etc.). Closes #309 - • Look in the metaclass, if defined, for members not found in the current class. Closes #306 - • Don't emit protected-access / W0212 \<#protected-access\> if the attribute is accessed using a property defined at the class level. - • Detect calls of the parent's \_\_init\_\_, through a binded super() call. - • Check that a class has an explicitly defined metaclass before emitting 'old-style-class' for Python 2. - • Emit catching-non-exception / E0712 \<#catching-non-exception\> for non-class nodes. Closes #303 - • Order of reporting is consistent. - • Add a new warning, boolean-datetime / W1502 \<#boolean-datetime\>, emitted when an instance of 'datetime.time' is used in a boolean context. Closes #239 - • Fix a crash which occurred while checking for method-hidden / E0202 \<#method-hidden\>, when the parent frame was something different than a function. - • Generate html output for missing files. Closes #320 - • Fix a false positive with too-many-format-args / E1305 \<#too-many-format-args\>, when the format string contains mixed attribute access arguments and manual fields. Closes #322 - • Extend the cases where undefined-variable / E0602 \<#undefined-variable\> and used-before-assignment / E0601 \<#used-before-assignment\> can be detected. Closes #291 - • Add support for customising callback identifiers, by adding a new '--callbacks' command line option. Closes #326 - • Add a new warning, logging-format-interpolation / W1202 \<#logging-format-interpolation\>, emitted when .format() string interpolation is used within logging function calls. - • Don't emit unbalanced-tuple-unpacking / W0632 \<#unbalanced-tuple-unpacking\> when the rhs of the assignment is a variable length argument. Closes #329 - • Add a new warning, inherit-non-class / E0239 \<#inherit-non-class\>, emitted when a class inherits from something which is not a class. Closes #331 - • Fix another false positives with undefined-variable / E0602 \<#undefined-variable\>, where the variable can be found as a class assignment and used in a function annotation. Closes #342 - • Handle assignment of the string format method to a variable. Closes #351 - • Support wheel packaging format for PyPi. Closes #334 - • Check that various built-ins that do not exist in Python 3 are not used: apply, basestring, buffer, cmp, coerce, execfile, file, long raw\_input, reduce, StandardError, unicode, reload and xrange. - • Warn for magic methods which are not used in any way in Python 3: \_\_coerce\_\_, \_\_delslice\_\_, \_\_getslice\_\_, \_\_setslice\_\_, \_\_cmp\_\_, \_\_oct\_\_, \_\_nonzero\_\_ and \_\_hex\_\_. - • Don't emit assigning-non-slot / E0237 \<#assigning-non-slot\> when the assignment is for a property. Closes #359 - • Fix for regression: '{path}' was no longer accepted in '--msg-template'. - • Report the percentage of all messages, not just for errors and warnings. Closes #319 - • too-many-public-methods / R0904 \<#too-many-public-methods\> is reported only for methods defined in a class, not in its ancestors. Closes #248 - • too-many-lines / C0302 \<#too-many-lines\> disable pragma can be located on any line, not only the first. Closes #321 - • Warn in Python 2 when an import statement is found without a corresponding **from \_\_future\_\_ import absolute\_import**. - • Warn in Python 2 when a non-floor division operation is found without a corresponding **from \_\_future\_\_ import division**. - • Add a new option, 'exclude-protected', for excluding members from the protected-access / W0212 \<#protected-access\> warning. Closes #48 - • Warn in Python 2 when using dict.iter\*(), dict.view\*(); none of these methods are available in Python 3. - • Warn in Python 2 when calling an object's next() method; Python 3 uses \_\_next\_\_() instead. - • Warn when assigning to \_\_metaclass\_\_ at a class scope; in Python 3 a metaclass is specified as an argument to the 'class' statement. - • Warn when performing parameter tuple unpacking; it is not supported in Python 3. - • abstract-class-instantiated / E0110 \<#abstract-class-instantiated\> is also emitted for Python 2. It was previously disabled. - • Add 'long-suffix' error, emitted when encountering the long suffix on numbers. - • Add support for disabling a checker, by specifying an 'enabled' attribute on the checker class. - • Add a new CLI option, --py3k, for enabling Python 3 porting mode. This mode will disable all other checkers and will emit warnings and errors for constructs which are invalid or removed in Python 3. - • Add 'old-octal-literal' to Python 3 porting checker, emitted when encountering octals with the old syntax. - • Add 'implicit-map-evaluation' to Python 3 porting checker, emitted when encountering the use of map builtin, without explicit evaluation. ### What's New In Pylint 1.3 Release date: 2014-07-26 - • Allow hanging continued indentation for implicitly concatenated strings. Closes #232. - • Pylint works under Python 2.5 again, and its test suite passes. - • Fix some false positives for the cellvar-from-loop warnings. Closes #233. - • Return new astroid class nodes when the inferencer can detect that that result of a function invocation on a type (like **type** or *abc.ABCMeta*) is requested. Closes #205. - • Emit undefined-variable / E0602 \<#undefined-variable\> for undefined names when using the Python 3 **metaclass=** argument. - • Checkers respect priority now. Closes #229 - • Fix a false positive regarding W0511. Closes #149. - • Fix unused-import / W0611 \<#unused-import\> false positive with Python 3 metaclasses Closes #143 - • Don't warn with bad-format-character / E1300 \<#bad-format-character\> when encountering the 'a' format on Python 3. - • Add multiple checks for PEP 3101 advanced string formatting: bad-format-string / W1302 \<#bad-format-string\>, missing-format-argument-key / W1303 \<#missing-format-argument-key\>, unused-format-string-argument / W1304 \<#unused-format-string-argument\>, format-combined-specification / W1305 \<#format-combined-specification\>, missing-format-attribute / W1306 \<#missing-format-attribute\> and invalid-format-index / W1307 \<#invalid-format-index\>. - • Issue broad-except / W0703 \<#broad-except\> and bare-except / W0702 \<#bare-except\> even if the number of except handlers is different than 1. Closes #113 - • Issue attribute-defined-outside-init / W0201 \<#attribute-defined-outside-init\> for all cases, not just for the last assignment. Closes #262 - • Emit not-callable / E1102 \<#not-callable\> when calling properties. Closes #268. - • Fix a false positive with unbalanced iterable unpacking, when encountering starred nodes. Closes #273. - • Add new checks, invalid-slice-index / E1127 \<#invalid-slice-index\> and invalid-sequence-index / E1126 \<#invalid-sequence-index\> for invalid sequence and slice indices. - • Add assigning-non-slot / E0237 \<#assigning-non-slot\> warning, which detects assignments to attributes not defined in slots. - • Don't emit no-name-in-module / E0611 \<#no-name-in-module\> for ignored modules. Closes #223. - • Fix an unused-variable / W0612 \<#unused-variable\> false positive, where the variable is assigned through an import. Closes #196. - • Definition order is considered for classes, function arguments and annotations. Closes #257. - • Don't emit unused-variable / W0612 \<#unused-variable\> when assigning to a nonlocal. Closes #275. - • Do not let ImportError propagate from the import checker, leading to crash in some namespace package related cases. Closes #203. - • Don't emit pointless-string-statement / W0105 \<#pointless-string-statement\> for attribute docstrings. Closes #193. - • Use the proper mode for pickle when opening and writing the stats file. Closes #148. - • Don't emit hidden-method message when the attribute has been monkey-patched, you're on your own when you do that. - • Only emit attribute-defined-outside-init / W0201 \<#attribute-defined-outside-init\> for definition within the same module as the offended class, avoiding to mangle the output in some cases. - • Don't emit unnecessary-lambda / W0108 \<#unnecessary-lambda\> if the body of the lambda call contains call chaining. Closes #243. - • Don't emit missing-docstring / C0111 \<#missing-docstring\> when the actual docstring uses **.format**. Closes #281. ### What's New In Pylint 1.2 Release date: 2014-04-30 - • Restore the ability to specify the init-hook option via the configuration file, which was accidentally broken in 1.2.0. - • Add a new warning \[bad-continuation\] for badly indented continued lines. - • Emit assignment-from-none / E1128 \<#assignment-from-none\> when the function contains bare returns. Closes BitBucket #191 - • Added a new warning for closing over variables that are defined in loops. Closes BitBucket #176 - • Do not warn about u escapes in string literals when Unicode literals are used for Python 2.\*. Closes BitBucket #151 - • Extend the checking for unbalanced-tuple-unpacking / W0632 \<#unbalanced-tuple-unpacking\> and unpacking-non-sequence / E0633 \<#unpacking-non-sequence\> to instance attribute unpacking as well. - • Fix explicit checking of python script (1.2 regression) Closes #219 - • Restore --init-hook, renamed accidentally into --init-hooks in 1.2.0 Closes #211 - • Add 'indexing-exception' warning, which detects that indexing an exception occurs in Python 2 (behaviour removed in Python 3). ### What's New in Pylint 1.2.0? Release date: 2014-04-18 - • Pass the current python paths to pylint process when invoked via epylint. Closes BitBucket #133. - • Add -i / --include-ids and -s / --symbols back as completely ignored options. Closes BitBucket #180. - • Extend the number of cases in which logging calls are detected. Closes BitBucket #182. - • Improve pragma handling to not detect pylint:\* strings in non-comments. Closes BitBucket #79. - • Do not crash with UnknownMessage if an unknown message ID/name appears in disable or enable in the configuration. Patch by Cole Robinson. Closes BitBucket #170 - • Add new warning eval-used / W0123 \<#eval-used\>, checking that the builtin function **eval** was used. - • Make it possible to show a naming hint for invalid name by setting include-naming-hint. Also make the naming hints configurable. Closes BitBucket #138 - • Added support for enforcing multiple, but consistent name styles for different name types inside a single module; based on a patch written by \. - • Also warn about empty docstrings on overridden methods; contributed by \. - • Also inspect arguments to constructor calls, and emit relevant warnings; contributed by \. - • Added a new configuration option logging-modules to make the list of module names that can be checked for logging-not-lazy / W1201 \<#logging-not-lazy\> et. al. configurable; contributed by \. - • ensure init-hooks is evaluated before other options, notably load-plugins Closes #166 - • Python 2.5 support restored: fixed small issues preventing pylint to run on python 2.5. Closes BitBucket #50 Closes BitBucket #62 - • pylint doesn't crash when looking for used-before-assignment / E0601 \<#used-before-assignment\> in context manager assignments. Closes BitBucket #128 - • Add new warning, bad-reversed-sequence / E0111 \<#bad-reversed-sequence\>, for checking that the reversed() builtin receive a sequence (implements **\_\_getitem\_\_** and **\_\_len\_\_**, without being a dict or a dict subclass) or an instance which implements **\_\_reversed\_\_**. - • Mark **file** as a bad function when using python2 Closes #8 - • Add new warning bad-exception-context / E0703 \<#bad-exception-context\>, checking that **raise ... from ...** uses a proper exception context (None or an exception). - • Enhance the check for used-before-assignment / E0601 \<#used-before-assignment\> to look for 'nonlocal' uses. - • Emit undefined-all-variable / E0603 \<#undefined-all-variable\> if a package's \_\_all\_\_ variable contains a missing submodule. Closes #126 - • Add a new warning abstract-class-instantiated / E0110 \<#abstract-class-instantiated\> for checking that abstract classes created with **abc** module and with abstract methods are instantiated. - • Do not warn about return-arg-in-generator / E0106 \<#return-arg-in-generator\> in Python 3.3+. - • Do not warn about abstract-method / W0223 \<#abstract-method\> when the abstract method is implemented through assignment Closes #155 - • Improve cyclic import detection in the case of packages, patch by Buck Golemon - • Add new warnings for checking proper class \_\_slots\_\_: **invalid-slots-object** and **invalid-slots**. - • Search for rc file in *~/.config/pylintrc* if *~/.pylintrc* doesn't exists Closes #121 - • Don't register the new style checker w/ python \>= 3 - • Fix unused-import / W0611 \<#unused-import\> false positive w/ augment assignment Closes #78 - • Fix access-member-before-definition / E0203 \<#access-member-before-definition\> false negative wrt aug assign Closes #164 - • Do not attempt to analyze non python file, e.g. .so file Closes #122 ### What's New In Pylint 1.1 Release date: 2013-12-22 - • Add new check for use of deprecated-pragma / I0022 \<#deprecated-pragma\> directives "pylint:disable-msg" or "pylint:enable-msg" which was previously emitted as a regular warn(). - • Avoid false used-before-assignment / E0601 \<#used-before-assignment\> for except handler defined identifier used on the same line. Closes #111 - • Combine 'no-space-after-operator', 'no-space-after-comma' and 'no-space-before-operator' into a new warning 'bad-whitespace'. - • Add a new warning superfluous-parens / C0325 \<#superfluous-parens\> for unnecessary parentheses after certain keywords. - • Fix a potential crash in the redefine-in-handler warning if the redefined name is a nested getattr node. - • Add a new option for the multi-statement warning to allow single-line if statements. - • Add bad-context-manager / E0235 \<#bad-context-manager\> error, checking that '\_\_exit\_\_' special method accepts the right number of arguments. - • Run pylint as a python module 'python -m pylint' (Anatoly Techtonik). - • Check for non-exception classes inside an except clause. - • epylint support options to give to pylint after the file to analyze and have basic input validation, patches provided by felipeochoa and Brian Lane. Closes BitBucket #53 Closes BitBucket #54 - • Added a new warning, non-iterator-returned / E0301 \<#non-iterator-returned\>, for non-iterators returned by '\_\_iter\_\_'. - • Add new checks for unpacking non-sequences in assignments (unpacking-non-sequence / E0633 \<#unpacking-non-sequence\>) as well as unbalanced tuple unpacking (unbalanced-tuple-unpacking / W0632 \<#unbalanced-tuple-unpacking\>). - • useless-else-on-loop / W0120 \<#useless-else-on-loop\> not emitted if there is a break in the else clause of inner loop. Closes #117 - • don't mark **input** as a bad function when using python3. Closes #110 - • badly-implemented-container caused several problems in its current implementation. Deactivate it until we have something better. Refs #112 - • Use attribute regexp for properties in python3, as in python2 - • Create the **PYLINTHOME** directory when needed, it might fail and lead to spurious warnings on import of pylint.config. - • Fix setup.py so that pylint properly install on Windows when using python3 - • Various documentation fixes and enhancements - • Fix a false-positive trailing-whitespace / C0303 \<#trailing-whitespace\> on Windows Closes #55 ### What's New In Pylint 1.0 Release date: 2013-08-06 - • Add check for the use of 'exec' function - • New --msg-template option to control output, deprecating "msvc" and "parseable" output formats as well as killing **--include-ids** and **--symbols** options - • Do not emit \[fixme\] for every line if the config value 'notes' is empty, but \[fixme\] is enabled. - • Emit warnings about lines exceeding the column limit when those lines are inside multiline docstrings. - • Do not double-check parameter names with the regex for parameters and inline variables. - • Added a new warning missing-final-newline / C0304 \<#missing-final-newline\> for files missing the final newline. - • Methods that are decorated as properties are now treated as attributes for the purposes of name checking. - • Names of derived instance class member are not checked any more. - • Names in global statements are now checked against the regular expression for constants. - • For toplevel name assignment, the class name regex will be used if pylint can detect that value on the right-hand side is a class (like collections.namedtuple()). - • Simplified invalid-name / C0103 \<#invalid-name\> message - • Added a new warning invalid-encoded-data (W0512) for files that contain data that cannot be decoded with the specified or default encoding. - • New warning bad-open-mode / W1501 \<#bad-open-mode\> for calls to open (or file) that specify invalid open modes (Original implementation by Sasha Issayev). - • New warning old-style-class (C1001) for classes that do not have any base class. - • Add new name type 'class\_attribute' for attributes defined in class scope. By default, allow both const and variable names. - • New warning trailing-whitespace / C0303 \<#trailing-whitespace\> that warns about trailing whitespace. - • Added a new warning unpacking-in-except (W0712) about unpacking exceptions in handlers, which is unsupported in Python 3. - • Add a configuration option for missing-docstring / C0111 \<#missing-docstring\> to optionally exempt short functions/methods/classes from the check. - • Add the type of the offending node to missing-docstring / C0111 \<#missing-docstring\> and empty-docstring / C0112 \<#empty-docstring\>. - • New utility classes for per-checker unittests in testutils.py - • Do not warn about redefinitions of variables that match the dummy regex. - • Do not treat all variables starting with \_ as dummy variables, only \_ itself. - • Make the line-too-long / C0301 \<#line-too-long\> warning configurable by adding a regex for lines for with the length limit should not be enforced - • Do not warn about a long line if a pylint disable option brings it above the length limit - • Do not flag names in nested with statements as undefined. - • Added a new warning 'old-raise-syntax' for the deprecated syntax raise Exception, args - • Support for PEP 3102 and new missing-kwoa / E1125 \<#missing-kwoa\> message for missing mandatory keyword argument Closes Logilab #107788 - • Fix spelling of max-branchs option, now max-branches - • Added a new base class and interface for checkers that work on the tokens rather than the syntax, and only tokenize the input file once. - • Follow astng renaming to astroid - • Check for unbalanced unpacking in assignments Closes BitBucket #37 - • Fix incomplete-protocol false positive for read-only containers like tuple Closes BitBucket #25 - • Fix False positive E1003 on Python 3 for argument-less super() Closes BitBucket #16 - • Put back documentation in source distribution Closes BitBucket #6 - • epylint shouldn't hang anymore when there is a large output on pylint'stderr Closes BitBucket #15 - • Fix epylint w/ python3 Closes BitBucket #7 - • Remove string module from the default list of deprecated modules Closes BitBucket #3 ### 0.x From pylint's beginning to pylint 2.14.0 included, we had a changelog that contained *all* nontrivial changes to Pylint, including changes that were not user facing, i.e. change that might interest you only if you're a developer working on pylint or pylint plugins or an open-source historian. Ticket numbers are almost always internal to Logilab, some come from bitbucket. ### What's New in Pylint 0.28.0? Release date: 2013-04-25 - • bitbucket #1: fix "dictionary changed size during iteration" crash - • \#74013: new E1310\[bad-str-strip-call\] message warning when a call to a {l,r,}strip method contains duplicate characters (patch by Torsten Marek) - • \#123233: new E0108\[duplicate-argument-name\] message reporting duplicate argument names - • \#81378: emit W0120\[useless-else-on-loop\] for loops without break - • \#124660: internal dependencies should not appear in external dependencies report - • \#124662: fix name error causing crash when symbols are included in output messages - • \#123285: apply pragmas for warnings attached to lines to physical source code lines - • \#123259: do not emit E0105 for yield expressions inside lambdas - • \#123892: don't crash when attempting to show source code line that can't be encoded with the current locale settings - • Simplify checks for dangerous default values by unifying tests for all different mutable compound literals. - • Improve the description for redundant-keyword-arg / E1124 \<#redundant-keyword-arg\> ### What's New in Pylint 0.27.0? Release date: 2013-02-26 - • \#20693: replace pylint.el by Ian Eure version (patch by J.Kotta) - • \#105327: add support for --disable=all option and deprecate the 'disable-all' inline directive in favour of 'skip-file' (patch by A.Fayolle) - • \#110840: add messages I0020 and I0021 for reporting of suppressed messages and useless suppression pragmas. (patch by Torsten Marek) - • \#112728: add warning E0604 for non-string objects in \_\_all\_\_ (patch by Torsten Marek) - • \#120657: add warning W0110/deprecated-lambda when a map/filter of a lambda could be a comprehension (patch by Martin Pool) - • \#113231: logging checker now looks at instances of Logger classes in addition to the base logging module. (patch by Mike Bryant) - • \#111799: don't warn about octal escape sequence, but warn about o which is not octal in Python (patch by Martin Pool) - • \#110839: bind \ to Run button in pylint-gui - • \#115580: fix erroneous W0212 (access to protected member) on super call (patch by Martin Pool) - • \#110853: fix a crash when an \_\_init\_\_ method in a base class has been created by assignment rather than direct function definition (patch by Torsten Marek) - • \#110838: fix pylint-gui crash when include-ids is activated (patch by Omega Weapon) - • \#112667: fix emission of reimport warnings for mixed imports and extend the testcase (patch by Torsten Marek) - • \#112698: fix crash related to non-inferable \_\_all\_\_ attributes and invalid \_\_all\_\_ contents (patch by Torsten Marek) - • Python 3 related fixes: - • - **#110213: fix import of checkers broken with python 3.3, causing** "No such message id W0704" breakage - • \#120635: redefine cmp function used in pylint.reporters - • Include full warning id for I0020 and I0021 and make sure to flush warnings after each module, not at the end of the pylint run. (patch by Torsten Marek) - • Changed the regular expression for inline options so that it must be preceded by a # (patch by Torsten Marek) - • Make dot output for import graph predictable and not depend on ordering of strings in hashes. (patch by Torsten Marek) - • Add hooks for import path setup and move pylint's sys.path modifications into them. (patch by Torsten Marek) ### What's New in Pylint 0.26.0? Release date: 2012-10-05 - • \#106534: add --ignore-imports option to code similarity checking and 'symilar' command line tool (patch by Ry4an Brase) - • \#104571: check for anomalous backslash escape, introducing new W1401 and W1402 messages (patch by Martin Pool) - • \#100707: check for boolop being used as exception class, introducing new W0711 message (patch by Tim Hatch) - • \#4014: improve checking of metaclass methods first args, introducing new C0204 message (patch by \ finalized by sthenault) - • \#4685: check for consistency of a module's \_\_all\_\_ variable, introducing new E0603 message - • \#105337: allow custom reporter in output-format (patch by Kevin Jing Qiu) - • \#104420: check for protocol completeness and avoid false R0903 (patch by Peter Hammond) - • \#100654: fix grammatical error for W0332 message (using 'l' as long int identifier) - • \#103656: fix W0231 false positive for missing call to object.\_\_init\_\_ (patch by \) - • \#63424: fix similarity report disabling by properly renaming it to RP0801 - • \#103949: create a console\_scripts entry point to be used by easy\_install, buildout and pip - • fix cross-interpreter issue (non compatible access to \_\_builtins\_\_) - • stop including tests files in distribution, they causes crash when installed with python3 (#72022, #82417, #76910) ### What's New in Pylint 0.25.2? Release date: 2012-07-17 - • \#93591: Correctly emit warnings about clobbered variable names when an except handler contains a tuple of names instead of a single name. (patch by \) - • \#7394: W0212 (access to protected member) not emitted on assignments (patch by \) - • \#18772; no prototype consistency check for mangled methods (patch by \) - • \#92911: emit W0102 when sets are used as default arguments in functions (patch by \) - • \#77982: do not emit E0602 for loop variables of comprehensions used as argument values inside a decorator (patch by \) - • \#89092: don't emit E0202 (attribute hiding a method) on @property methods - • \#92584: fix pylint-gui crash due to internal API change - • \#87192: fix crash when decorators are accessed through more than one dot (for instance @a.b is fine, @a.b.c crash) - • \#88914: fix parsing of --generated-members options, leading to crash when using a regexp value set - • fix potential crashes with utils.safe\_infer raising InferenceError ### What's New in Pylint 0.25.1? Release date: 2011-12-08 - • \#81078: Warn if names in exception handlers clobber overwrite existing names (patch by \) - • \#81113: Fix W0702 messages appearing with the wrong line number. (patch by \) - • \#50461, #52020, #51222: Do not issue warnings when using 2.6's property.setter/deleter functionality (patch by \) - • \#9188, #4024: Do not trigger W0631 if a loop variable is assigned in the else branch of a for loop. ### What's New in Pylint 0.25.0? Release date: 2011-10-7 - • \#74742: make allowed name for first argument of class method configurable (patch by Google) - • \#74087: handle case where inference of a module return YES; this avoid some cases of "TypeError: '\_Yes' object does not support indexing" (patch by Google) - • \#74745: make "too general" exception names configurable (patch by Google) - • \#74747: crash occurs when lookup up a special attribute in class scope (patch by google) - • \#76920: crash if on e.g. "pylint --rcfile" (patch by Torsten Marek) - • \#77237: warning for E0202 may be very misleading - • \#73941: HTML report messages table is badly rendered ### What's New in Pylint 0.24.0? Release date: 2011-07-18 - • \#69738: add regular expressions support for "generated-members" - • ids of logging and string\_format checkers have been changed: logging: 65 -\> 12, string\_format: 99 -\> 13 Also add documentation to say that ids of range 1-50 shall be reserved to pylint internal checkers - • \#69993: Additional string format checks for logging module: check for missing arguments, too many arguments, or invalid string formats in the logging checker module. Contributed by Daniel Arena - • \#69220: add column offset to the reports. If you've a custom reporter, this change may break it has now location gain a new item giving the column offset. - • \#60828: Fix false positive in reimport check - • \#70495: absolute imports fail depending on module path (patch by Jacek Konieczny) - • \#22273: Fix --ignore option documentation to match reality ### What's New in Pylint 0.23.0? Release date: 2011-01-11 - • documentation update, add manpages - • several performance improvements - • finalize python3 support - • new W0106 warning 'Expression "%s" is assigned to nothing' - • drop E0501 and E0502 messages about wrong source encoding: not anymore interesting since it's a syntax error for python \>= 2.5 and we now only support this python version and above. - • don't emit W0221 or W0222 when methods as variable arguments (e.g. \*arg and/or \*\*args). Patch submitted by Charles Duffy. ### What's New in Pylint 0.22.0? Release date: 2010-11-15 - • python versions: minimal python3.x support; drop python \< 2.5 support ### What's New in Pylint 0.21.4? Release date: 2010-10-27 - • fix #48066: pylint crashes when redirecting output containing non-ascii characters - • fix #19799: "pylint -blah" exit with status 2 - • update documentation ### What's New in Pylint 0.21.3? Release date: 2010-09-28 - • restored python 2.3 compatibility. Along with logilab-astng 0.21.3 and logilab-common 0.52, this will much probably be the latest release supporting python \< 2.5. ### What's New in Pylint 0.21.2? Release date: 2010-08-26 - • fix #36193: import checker raise exception on cyclic import - • fix #28796: regression in --generated-members introduced pylint 0.20 - • some documentation cleanups ### What's New in Pylint 0.21.1? Release date: 2010-06-04 - • fix #28962: pylint crash with new options, due to missing stats data while writing the Statistics by types report - • updated man page to 0.21 or greater command line usage (fix debian #582494) ### What's New in Pylint 0.21.0? Release date: 2010-05-11 - • command line updated (closes #9774, #9787, #9992, #22962): - • all enable-\* / disable-\* options have been merged into --enable / --disable - • BACKWARD INCOMPATIBLE CHANGE: short name of --errors-only becomes -E, -e being affected to --enable - • pylint --help output much simplified, with --long-help available to get the complete one - • revisited gui, thanks to students from Toronto university (they are great contributors to this release!) - • fix #21591: html reporter produces no output if reports is set to 'no' - • fix #4581: not Missing docstring (C0111) warning if a method is overridden - • fix #4683: Non-ASCII characters count double if utf8 encode - • fix #9018: when using defining-attr-method, method order matters - • fix #4595: Comma not followed by a space should not occurs on trailing comma in list/tuple/dict definition - • fix #22585: \[Patch\] fix man warnings for pyreverse.1 manpage - • fix #20067: AttributeError: 'NoneType' object has no attribute 'name' with with ### What's New in Pylint 0.20.0? Release date: 2010-03-01 - • fix #19498: fix windows batch file - • fix #19339: pylint.el : non existing py-mod-map (closes Debian Bug report logs - #475939) - • implement #18860, new W0199 message on assert (a, b) - • implement #9776, 'W0150' break or return statement in finally block may swallow exception. - • fix #9263, \_\_init\_\_ and \_\_new\_\_ are checked for unused arguments - • fix #20991, class scope definitions ignored in a genexpr - • fix #5975, Abstract intermediate class not recognized as such - • fix #5977, yield and return statement have their own counters, no more R0911 (Too many return statements) when a function have many yield stamtements - • implement #5564, function / method arguments with leading "\_" are ignored in arguments / local variables count. - • implement #9982, E0711 specific error message when raising NotImplemented - • remove --cache-size option ### What's New in Pylint 0.19.0? Release date: 2009-12-18 - • implement #18947, #5561: checker for function arguments - • include James Lingard string format checker - • include simple message (ids) listing by Vincent Ferotin (#9791) - • \--errors-only does not hide fatal error anymore - • include james Lingard patches for ++/-- and duplicate key in dicts - • include James Lingard patches for function call arguments checker - • improved Flymake code and doc provided by Derek Harland - • refactor and fix the imports checker - • fix #18862: E0601 false positive with lambda functions - • fix #8764: More than one statement on a single line false positive with try/except/finally - • fix #9215: false undefined variable error in lambda function - • fix for w0108 false positive (Nathaniel) - • fix test/fulltest.sh - • \#5821 added a utility function to run pylint in another process (patch provide by Vincent Ferotin) ### What's New in Pylint 0.18.0? Release date: 2009-03-25 - • tests ok with python 2.4, 2.5, 2.6. 2.3 not tested - • fix #8687, W0613 false positive on inner function - • fix #8350, C0322 false positive on multi-line string - • fix #8332: set E0501 line no to the first line where non ascii character has been found - • avoid some E0203 / E0602 false negatives by detecting respectively AttributeError / NameError - • implements #4037: don't issue W0142 (\* or \*\* magic) when they are barely passed from */\** arguments - • complete #5573: more complete list of special methods, also skip W0613 for python internal method - • don't show information messages by default - • integration of Yuen Ho Wong's patches on Emacs lisp files ### What's New in Pylint 0.17.0? Release date: 2009-03-19 - • semicolon check : move W0601 to W0301 - • remove rpython : remove all rpython checker, modules and tests - • astng 0.18 compatibility: support for \_ast module modifies interfaces ### What's New in Pylint 0.16.0? Release date: 2009-01-28 - • change \[en\|dis\]able-msg-cat options: only accept message categories identified by their first letter (e.g. IRCWEF) without the need for comma as separator - • add epylint.bat script to fix Windows installation - • setuptools/easy\_install support - • include a modified version of Maarten ter Huurne patch to avoid W0613 warning on arguments from overridden method - • implement #5575 drop dumb W0704 message) by adding W0704 to ignored messages by default - • new W0108 message, checking for suspicious lambda (provided by Nathaniel Manista) - • fix W0631, false positive reported by Paul Hachmann - • fix #6951: false positive with W0104 - • fix #6949 - • patches by Mads Kiilerich: - • implement #4691, make pylint exits with a non zero return status if any messages other then Information are issued - • fix #3711, #5626 (name resolution bug w/ decorator and class members) - • fix #6954 ### What's New in Pylint 0.15.2? Release date: 2008-10-13 - • fix #5672: W0706 weirdness ( W0706 removed ) - • fix #5998: documentation points to wrong url for mailing list - • fix #6022: no error message on wrong module names - • fix #6040: pytest doesn't run test/func\_test.py ### What's New in Pylint 0.15.1? Release date: 2008-09-15 - • fix #4910: default values are missing in manpage - • fix #5991: missing files in 0.15.0 tarball - • fix #5993: epylint should work with python 2.3 ### What's New in Pylint 0.15.0? Release date: 2008-09-10 - • include pyreverse package and class diagram generation - • included Stefan Rank's patch to deal with 2.4 relative import - • included Robert Kirkpatrick's tutorial and typos fixes - • fix bug in reenabling message - • fix #2473: invoking pylint on \_\_init\_\_.py (hopefully) - • typecheck: acquired-members option has been dropped in favor of the more generic generated-members option. If the zope option is set, the behaviour is now to add some default values to generated-members. - • Flymake integration: added bin/epylint and elisp/pylint-flymake.el ### What's New in Pylint 0.14.0? Release date: 2008-01-14 - • fix #3733: Messages (dis)appear depending on order of file names - • fix #4026: pylint.el should require compile - • fix a bug in colorized reporter, spotted by Dave Borowitz - • applied patch from Stefan Rank to avoid W0410 false positive when multiple "from \_\_future\_\_" import statements - • implement #4012: flag back tick as deprecated (new W0333 message) - • new ignored-class option on typecheck checker allowing to skip members checking based on class name (patch provided by Thomas W Barr) ### What's New in Pylint 0.13.2? Release date: 2007-06-07 - • fix disable-checker option so that it won't accidentally enable the rpython checker which is disabled by default - • added note about the gedit plugin into documentation ### What's New in Pylint 0.13.1? Release date: 2007-03-02 - • fix some unexplained 0.13.0 packaging issue which led to a bunch of files missing from the distribution ### What's New in Pylint 0.13.0? Release date: 2007-02-28 - • new RPython (Restricted Python) checker for PyPy fellow or people wanting to get a compiled version of their python program using the translator of the PyPy project. For more information about PyPy or RPython, visit \, previously codespeak.net/pypy/ - • new E0104 and E0105 messages introduced to respectively warn about "return" and "yield" outside function or method - • new E0106 message when "yield" and "return something" are mixed in a function or method - • new W0107 message for unnecessary pass statement - • new W0614 message to differentiate between unused **import X** and unused *from X import \** (#3209, patch submitted by Daniel Drake) - • included Daniel Drake's patch to have a different message E1003 instead of E1001 when a missing member is found but an inference failure has been detected - • msvs reporter for Visual Studio line number reporting (#3285) - • allow disable-all option inline (#3218, patch submitted by Daniel Drake) - • \--init-hook option to call arbitrary code necessary to set environment (e.g. sys.path) (#3156) - • One more Daniel's patch fixing a command line option parsing problem, this'll definitely be the DDrake release :) - • fix #3184: crashes on "return" outside function - • fix #3205: W0704 false positive - • fix #3123: W0212 false positive on static method - • fix #2485: W0222 false positive - • fix #3259: when a message is explicitly enabled, check the checker emitting it is enabled ### What's New in Pylint 0.12.2? Release date: 2006-11-23 - • fix #3143: W0233 bug w/ YES objects - • fix #3119: Off-by-one error counting lines in a file - • fix #3117: ease sys.stdout overriding for reporters - • fix #2508: E0601 false positive with lambda - • fix #3125: E1101 false positive and a message duplication. Only the last part is actually fixed since the initial false positive is due to dynamic setting of attributes on the decimal.Context class. - • fix #3149: E0101 false positives and introduced E0100 for generator \_\_init\_\_ methods - • fixed some format checker false positives ### What's New in Pylint 0.12.1? Release date: 2006-09-25 - • fixed python \>= 2.4 format false positive with multiple lines statement - • fixed some 2.5 issues - • fixed generator expression scope bug (depends on astng 0.16.1) - • stop requiring \_\_revision\_\_ ### What's New in Pylint 0.12.0? Release date: 2006-08-10 - • usability changes: - • parseable, html and color options are now handled by a single output-format option - • enable-\ and disable-all options are now handled by two (exclusive) enable-checker and disable-checker options taking a comma separated list of checker names as value - • renamed debug-mode option to errors-only - • started a reference user manual - • new W0212 message for access to protected member from client code (Closes #14081) - • new W0105 and W0106 messages extracted from W0104 (statement seems to have no effect) respectively when the statement is actually string (that's sometimes used instead of comments for documentation) or an empty statement generated by a useless semicolon - • reclassified W0302 to C0302 - • fix so that global messages are not anymore connected to the last analyzed module (Closes #10106) - • fix some bugs related to local disabling of messages - • fix cr/lf pb when generating the rc file on windows platforms ### What's New in Pylint 0.11.0? Release date: 2006-04-19 - • fix crash caused by the exceptions checker in some case - • fix some E1101 false positive with abstract method or classes defining \_\_getattr\_\_ - • dirty fix to avoid "\_socketobject" has not "connect" member. The actual problem is that astng isn't able to understand the code used to create socket.socket object with exec - • added an option in the similarity checker to ignore docstrings, enabled by default - • included patch from Benjamin Niemann to allow block level enabling/disabling of messages ### What's New in Pylint 0.10.0? Release date: 2006-03-06 - • WARNING, this release include some configuration changes (see below), so you may have to check and update your own configuration file(s) if you use one - • this release require the 0.15 version of astng or superior (it will save you a lot of pylint crashes...) - • W0705 has been reclassified to E0701, and is now detecting more inheriting problem, and a false positive when empty except clause is following an Exception catch has been fixed (Closes #10422) - • E0212 and E0214 (metaclass/class method should have mcs/cls as first argument have been reclassified to C0202 and C0203 since this not as well established as "self" for instance method (E0213) - • W0224 has been reclassified into F0220 (failed to resolve interfaces implemented by a class) - • a new typecheck checker, introducing the following checks: - • E1101, access to nonexistent member (implements #10430), remove the need of E0201 and so some options has been moved from the classes checker to this one - • E1102, calling a non callable object - • E1111 and W1111 when an assignment is done on a function call but the inferred function returns None (implements #10431) - • change in the base checker: - • checks module level and instance attribute names (new const-rgx and attr-rgx configuration option) (implements #10209 and #10440) - • list comprehension and generator expression variables have their own regular expression (the inlinevar-rgx option) (implements #9146) - • the C0101 check with its min-name-length option has been removed (this can be specified in the regxp after all...) - • W0103 and W0121 are now handled by the variables checker (W0103 is now W0603 and W0604 has been split into different messages) - • W0131 and W0132 messages have been reclassified to C0111 and C0112 respectively - • new W0104 message on statement without effect - • regexp support for dummy-variables (dummy-variables-rgx option replace dummy-variables) (implements #10027) - • better global statement handling, see W0602, W0603, W0604 messages (implements #10344 and #10236) - • \--debug-mode option, disabling all checkers without error message and filtering others to only display error - • fixed some R0201 (method could be a function) false positive ### What's New in Pylint 0.9.0? Release date: 2006-01-10 - • a lot of updates to follow astng 0.14 API changes, so install logilab-astng 0.14 or greater before using this version of pylint - • checker number 10 ! newstyle will search for problems regarding old style / new style classes usage problems (rely on astng 0.14 new style detection feature) - • new 'load-plugins' options to load additional pylint plugins (usable from the command line or from a configuration file) (implements #10031) - • check if a "pylintrc" file exists in the current working directory before using the one specified in the PYLINTRC environment variable or the default ~/.pylintrc or /etc/pylintrc - • fixed W0706 (Identifier used to raise an exception is assigned...) false positive and reraising a caught exception instance - • fixed E0611 (No name get in module blabla) false positive when accessing to a class'\_\_dict\_\_ - • fixed some E0203 ("access to member before its definition") false positive - • fixed E0214 ("metaclass method first argument should be mcs) false positive with staticmethod used on a metaclass - • fixed packaging which was missing the test/regrtest\_data directory - • W0212 (method could be a function) has been reclassified in the REFACTOR category as R0201, and is no more considerer when a method overrides an abstract method from an ancestor class - • include module name in W0401 (wildcard import), as suggested by Amaury - • when using the '--parseable', path are written relative to the current working directory if in a sub-directory of it (#9789) - • 'pylint --version' shows logilab-astng and logilab-common versions - • fixed pylint.el to handle space in file names - • misc lint style fixes ### What's New in Pylint 0.8.1? Release date: 2005-11-07 - • fix "deprecated module" false positive when the code imports a module whose name starts with a deprecated module's name (close #10061) - • fix "module has no name \_\_dict\_\_" false positive (Closes #10039) - • fix "access to undefined variable \_\_path\_\_" false positive (close #10065) - • fix "explicit return in \_\_init\_\_" false positive when return is actually in an inner function (Closes #10075) ### What's New in Pylint 0.8.0? Release date: 2005-10-21 - • check names imported from a module exists in the module (E0611), patch contributed by Amaury Forgeot d'Arc - • print a warning (W0212) for methods that could be a function (implements #9100) - • new --defining-attr-methods option on classes checker - • new --acquired-members option on the classes checker, used when --zope=yes to avoid false positive on acquired attributes (listed using this new option) (Closes #8616) - • generate one E0602 for each use of an undefined variable (previously, only one for the first use but not for the following) (implements #1000) - • make profile option saveable - • fix Windows .bat file, patch contributed by Amaury Forgeot d'Arc - • fix one more false positive for E0601 (access before definition) with for loop such as "for i in range(10): print i" (test func\_noerror\_defined\_and\_used\_on\_same\_line) - • fix false positive for E0201 (undefined member) when accessing to \_\_name\_\_ on a class object - • fix astng checkers traversal order - • fix bug in format checker when parsing a file from a platform using different new line characters (Closes #9239) - • fix encoding detection regexp - • fix --rcfile handling (support for --rcfile=file, Closes #9590) ### What's New in Pylint 0.7.0? Release date: 2005-05-27 - • WARNING: pylint is no longer a logilab subpackage. Users may have to manually remove the old logilab/pylint directory. - • introduce a new --additional-builtins option to handle user defined builtins - • \--reports option has now -r as short alias, and -i for --include-ids - • fix a bug in the variables checker which may causing some false positives when variables are defined and used within the same statement (test func\_noerror\_defined\_and\_used\_on\_same\_line) - • this time, real fix of the "disable-msg in the config file" problem, test added to unittest\_lint - • fix bug with --list-messages and python -OO - • fix possible false positive for W0201 ### What's New in Pylint 0.6.4? Release date: 2005-04-14 - • allow to parse files without extension when a path is given on the command line (test noext) - • don't fail if we are unable to read an inline option (e.g. inside a module), just produce an information message (test func\_i0010) - • new message E0103 for break or continue outside loop (Closes #8883, test func\_continue\_not\_in\_loop) - • fix bug in the variables checker, causing non detection of some actual name error (Closes #8884, test func\_nameerror\_on\_string\_substitution) - • fix bug in the classes checker which was making pylint crash if "object" is assigned in a class inheriting from it (test func\_noerror\_object\_as\_class\_attribute) - • fix problem with the similar checker when related options are defined in a configuration file - • new --generate-man option to generate pylint's man page (require the latest logilab.common (\>= 0.9.3) - • packaged (generated...) man page ### What's New in Pylint 0.6.3? Release date: 2005-02-24 - • fix scope problem which may cause false positive and true negative on E0602 - • fix problem with some options such as disable-msg causing error when they are coming from the configuration file ### What's New in Pylint 0.6.2? Release date: 2005-02-16 - • fix false positive on E0201 ("access to undefined member") with metaclasses - • fix false positive on E0203 ("access to member before its definition") when attributes are defined in a parent class - • fix false positive on W0706 ("identifier used to raise an exception assigned to...") - • fix interpretation of "t" as value for the indent-string configuration variable - • fix --rcfile so that --rcfile=pylintrc (only --rcfile pylintrc was working in earlier release) - • new raw checker example in the examples/ directory ### What's New in Pylint 0.6.1? Release date: 2005-02-04 - • new --rcfile option to specify the configuration file without the PYLINTRC environment variable - • added an example module for a custom pylint checker (see the example/ directory) - • some fixes to handle fixes in common 0.9.1 (should however still working with common 0.9.0, even if upgrade is recommended) ### What's New in Pylint 0.6.0? Release date: 2005-01-20 - • refix pylint Emacs mode - • no more traceback when just typing "pylint" - • fix a bug which may cause crashes on resolving parent classes - • fix problems with the format checker: don't chock on files containing multiple CR, avoid C0322, C0323, C0324 false positives with triple quoted string with quote inside - • correctly detect access to member defined latter in \_\_init\_\_ method - • now depends on common 0.8.1 to fix problem with interface resolution (Closes #8606) - • new --list-msgs option describing available checkers and their messages - • added windows specific documentation to the README file, contributed by Brian van den Broek - • updated doc/features.txt (actually this file is now generated using the --list-msgs option), more entries into the FAQ - • improved tests coverage ### What's New in Pylint 0.5.0? Release date: 2004-10-19 - • avoid importing analyzed modules ! - • new Refactor and Convention message categories. Some Warnings have been remapped into those new categories - • added "similar", a tool to find copied and pasted lines of code, both using a specific command line tool and integrated as a pylint's checker - • imports checker may report import dependencies as a dot graph - • new checker regrouping most Refactor detection (with some new metrics) - • more command line options storable in the configuration file - • fix bug with total / undocumented number of methods ### What's New in Pylint 0.4.2? Release date: 2004-07-08 - • fix pylint Emacs mode - • fix classes checkers to handler twisted interfaces ### What's New in Pylint 0.4.1? Release date: 2004-05-14 - • fix the setup.py script to allow bdist\_winst (well, the generated installer has not been tested...) with the necessary logilab/\_\_init\_\_.py file - • fix file naming convention as suggested by Andreas Amoroso - • fix stupid crash bug with bad method names ### What's New in Pylint 0.4.0? Release date: 2004-05-10 - • fix file path with --parsable - • \--parsable option has been renamed to --parseable - • added patch from Andreas Amoroso to output message to files instead of standard output - • added Run to the list of correct variable names - • fix variable names regexp and checking of local classes names - • some basic handling of metaclasses - • no-docstring-rgx apply now on classes too - • new option to specify a different regexp for methods than for functions - • do not display the evaluation report when no statements has been analysed - • fixed crash with a class nested in a method - • fixed format checker to deals with triple quoted string and lines with code and comment mixed - • use logilab.common.ureports to layout reports ### What's New in Pylint 0.3.3? Release date: 2004-02-17 - • added a parsable text output, used when the --parsable option is provided - • added an Emacs mode using this output, available in the distrib's elisp directory - • fixed some typos in messages - • change include-ids options to yn, and allow it to be in the configuration file - • do not chock on corrupted stats files - • fixed bug in the format checker which may stop pylint execution - • provide scripts for unix and windows to wrap the minimal pylint tk gui ### What's New in Pylint 0.3.2? Release date: 2003-12-23 - • html-escape messages in the HTML reporter (bug reported by Juergen Hermann) - • added "TODO" to the list of default note tags - • added "rexec" to the list of default deprecated modules - • fixed typos in some messages ### What's New in Pylint 0.3.1? Release date: 2003-12-05 - • bug fix in format and classes checkers - • remove print statement from imports checkers - • provide a simple tk gui, essentially useful for windows users ### What's New in Pylint 0.3.0? Release date: 2003-11-20 - • new exceptions checker, checking for string exception and empty except clauses. - • imports checker checks for reimport of modules - • classes checker checks for calls to ancestor's \_\_init\_\_ and abstract method not overridden. It doesn't complain anymore for unused import in \_\_init\_\_ files, and provides a new option ignore-interface-methods, useful when you're using zope Interface implementation in your project - • base checker checks for disallowed builtins call (controlled by the bad-functions option) and for use of \* and \*\* - • format checker checks for use of \<\> and "l" as long int marker - • major internal API changes - • use the rewrite of astng, based on compiler.ast - • added unique id for messages, as suggested by Wolfgang Grafen - • added unique id for reports - • can take multiple modules or files as argument - • new options command line options : --disable-msg, --enable-msg, --help-msg, --include-ids, --reports, --disable-report, --cache-size - • \--version shows the version of the python interpreter - • removed some options which are now replaced by \[en\|dis\]able-msg, or disable-report - • read disable-msg and enable-msg options in source files (should be in comments on the top of the file, in the form "# pylint: disable-msg=W0402" - • new message for modules importing themselves instead of the "cyclic import" message - • fix bug with relative and cyclic imports - • fix bug in imports checker (cycle was not always detected) - • still fixes in format checker : don't check comment and docstring, check first line after an indent - • allowed/prohibited names now apply to all identifiers, not only variables, so changed the configuration option from (good\|bad)-variable-names to (good\|bad)-names - • added string, rexec and Bastion to the default list of deprecated modules - • do not print redefinition warning for function/class/method defined in mutually exclusive branches ### What's New in Pylint 0.2.1? Release date: 2003-10-10 - • added some documentation, fixed some typos - • set environment variable PYLINT\_IMPORT to 1 during pylint execution. - • check that variables "imported" using the global statement exist - • indentation problems are now warning instead of errors - • fix checkers.initialize to try to load all files with a known python extension (patch from wrobell) - • fix a bunch of messages - • fix sample configuration file - • fix the bad-construction option - • fix encoding checker - • fix format checker ### What's New in Pylint 0.2.0? Release date: 2003-09-12 - • new source encoding / FIXME checker (pep 263) - • new --zope option which trigger Zope import. Useful to check Zope products code. - • new --comment option which enable the evaluation note comment (disabled by default). - • a ton of bug fixes - • easy functional test infrastructure ### What's New in Pylint 0.1.2? Release date: 2003-06-18 - • bug fix release - • remove dependency to pyreverse ### What's New in Pylint 0.1.1? Release date: 2003-06-01 - • much more functionalities ! ### What's New in Pylint 0.1? Release date: 2003-05-19 - • initial release ### Frequently Asked Questions ### How do I install Pylint? For command line use, pylint is installed with: ``` pip install pylint ``` Or if you want to also check spelling with **enchant** (you might need to install the enchant C library \): ``` pip install pylint[spelling] ``` It can also be integrated in most editors or IDEs. More information can be found in the documentation \. ### How do I contribute to Pylint? We welcome all forms of contributions such as updates for documentation, new code, checking issues for duplicates or telling us that we can close them, confirming that issues still exist, creating issues because you found a bug or want a feature \, etc. Everything is much appreciated! Please follow the code of conduct \ and check the Contributor Guides \ if you want to make a code contribution. ### Does Pylint follow a versioning scheme? See upgrading pylint in the installation guide \<#upgrading-pylint\>. ### How do I find the name corresponding to a specific command line option? See the configuration documentation \<#all-configurations-options\>. ### What is the format of the configuration file? The configuration file can be an **ini** or **toml** file. See the exhaustive list of possible options \<#all-options\>. ### How to disable a particular message? Read Messages control \<#message-control\> for details and examples. ### Pylint gave my code a negative rating out of ten. That can't be right! Prior to Pylint 2.13.0, the score formula used by default had no lower bound. The new default score formula is ``` max(0, 0 if fatal else 10.0 - ((float(5 * error + warning + refactor + convention) / statement) * 10)) ``` If your project contains a configuration file created by an earlier version of Pylint, you can set **evaluation** to the above expression to get the new behavior. Likewise, since negative values are still technically supported, **evaluation** can be set to a version of the above expression that does not enforce a floor of zero. ### How do I avoid getting unused argument warnings for API I do not control? Prefix (ui) the callback's name by *cb\_* (callback), as in cb\_onclick(...). By doing so arguments usage won't be checked. Another solution is to use one of the names defined in the "dummy-variables" configuration variable for unused argument ("\_" and "dummy" by default). ### Why are there a bunch of messages disabled by default? Either because they are prone to false positives or that they are opinionated enough to not be included as default messages. You can see the plugin you need to explicitly load in the technical reference \<#optional-checkers\>. ### I want to run pylint on each keystroke in my IDE. How do I do that? Pylint full suite of checks will never be fast enough to run on every keystroke. However, some IDEs can run pylint when the IDE opens or saves files. See, for example, the Microsoft plugin for VS Code \. That said, pylint is best suited for linting on save for small projects, for continuous integration jobs, or a git **pre-push** hook for big projects. The larger your repository is, the slower pylint will be. If you want to make pylint faster for this type of use case, you can use the **--errors-only** option, which will remove all the refactor, convention, and warning checks. You can also disable checks with inherently high complexity that need to analyse the full code base like **duplicate-code** or **cyclic-import** (this list is not exhaustive). ### Why do I have non-deterministic results when I try to parallelize pylint ? pylint should analyse all your code at once in order to best infer the actual values that result from calls. If only some of the files are given, pylint might miss a particular value's type and produce inferior inference for the subset. Parallelization of pylint is not easy; we also discourage the use of the **-j** option if this matters to you. ### Which messages should I disable to avoid duplicates if I use other popular linters ? pycodestyle \: bad-indentation, bare-except, line-too-long, missing-final-newline, multiple-statements, singleton-comparison, trailing-newlines, trailing-whitespace, unnecessary-negation, unnecessary-semicolon, wrong-import-position pyflakes \: undefined-variable, unused-import, unused-variable mccabe \: too-many-branches pydocstyle \: missing-module-docstring, missing-class-docstring, missing-function-docstring pep8-naming \: invalid-name, bad-classmethod-argument, bad-mcs-classmethod-argument, no-self-argument isort \ and flake8-import-order \: ungrouped-imports, wrong-import-order ### How do I avoid "access to undefined member" messages in my mixin classes? You should add the **no-member** message to your **ignored-checks-for-mixins** option and name your mixin class with a name which ends with "Mixin" or "mixin" (default) or change the default value by changing the **mixin-class-rgx** option. ### Where is the persistent data stored to compare between successive runs? Analysis data are stored as a pickle file in a directory which is localized using the following rules: - • value of the PYLINTHOME environment variable if set - • - **"pylint" subdirectory of the user's XDG\_CACHE\_HOME if the environment variable is set, otherwise** - • Linux: "~/.cache/pylint" - • macOS: "~/Library/Caches/pylint" - • Windows: "C:Users\AppDataLocalpylint" - • ".pylint.d" directory in the current directory ### How does the website pylint dot org relate to this project? Historically, pylint dot org served as the primary website for Pylint. However, we no longer have access to the domain. The current owners are monetizing this by displaying advertisements alongside outdated documentation without contributing to pylint at all. For the latest and official Pylint documentation, please visit pylint.readthedocs.io \. Please see issue 8934 \ for more details. ### Contact ### Bug reports, feedback You think you have found a bug in Pylint? Well, this may be the case since Pylint and Python are under heavy development! Please take the time to check if it is already in the issue tracker at \ Note that the issue might also be reported in one of Pylint's major dependencies, astroid: - • \ ### Discord server You can discuss your problem using the discord server: \ ### Mailing lists The code-quality mailing list is shared with other tools that aim at improving the quality of python code. You can subscribe to this mailing list at \ Archives are available at \ Archives before April 2013 are not available anymore. At \ it was under **python-projects**. ### Support \[image: Tidelift\] \[image\] Professional support for pylint is available as part of the Tidelift Subscription \. Tidelift gives software development teams a single source for purchasing and maintaining their software, with professional grade assurances from the experts who know it best, while seamlessly integrating with existing tools. ## Author Logilab and Pylint contributors ## Copyright 2003-2026, Logilab and Pylint contributors