Linting Python in Visual Studio Code

Linting highlights syntactical and stylistic problems in your Python source code, which oftentimes helps you identify and correct subtle programming errors or unconventional coding practices that can lead to errors. For example, linting detects use of an uninitialized or undefined variable, calls to undefined functions, missing parentheses, and even more subtle issues such as attempting to redefine built-in types or functions. Linting is thus distinct from Formatting because linting analyzes how the code runs and detects errors whereas formatting only restructures how code appears.

By default, linting for Python is enabled in Visual Studio Code using Pylint, and you can enable other linters of your choice. You can easily enable and disable all linting by using the Python: Enable Linting command.

Enable linters

To enable linters other than the default PyLint, open the Command Palette (kb(workbench.action.showCommands)) and select the Python: Select Linter command. This command adds "python.linting.<linter>Enabled": true to your settings, where <linter> is the name of the chosen linter. See Specific linters for details.

Enabling a linter prompts you to install the required packages in your selected environment for the chosen linter.

Prompt for installing a linter

Note: If you're using a global environment and VS Code is not running elevated, linter installation may fail. In that case, either run VS Code elevated, or manually run the Python package manager to install the linter at an elevated command prompt for the same environment: for example sudo pip3 install pylint (macOS/Linux) or pip install pylint (Windows, at an elevated prompt)

Disable linting

You can disable all Python linting with the Python: Enable Linting command, which shows a dropdown with the current linting state and options to turn Python linting on or off.

Python Enable Linting command dropdown

Run linting

To perform linting:

Issues are shown in the Problems panel and as underlines in the code editor. Hovering over an underlined issue displays the details:

Linting messages in the editor and the Problems panel

General linting settings

The remainder of this article describes settings for linting in general as well as specific linters. You can add any of the settings to your user settings.json file (opened with the File > Preferences > Settings command kb(workbench.action.openSettings)). Refer to User and Workspace settings to find out more about working with settings in VS Code generally.

To change the linting behavior across all enabled linters, modify the following settings:

Feature Setting
(python.linting.)		 Default value
Linting in general enabled true
Linting on file save lintOnSave true
Maximum number of linting messages maxNumberOfProblems 100
Exclude file and folder patterns ignorePatterns [".vscode/*.py", "**/site-packages/**/*.py"]

You can easily change python.linting.enabled by using the Python: Enable Linting command.

When enabling lintOnSave, you might also want to enable the generic files.autoSave option (see Save / Auto Save). The combination provides frequent linting feedback in your code as you type.

Specific linters

The following table provides a summary of available Python linters and their basic settings. Only Pylint is enabled by default. For descriptions of individual settings, see the Linter settings reference.

Linter Package name for pip install command Default state True/false enable setting
(python.linting.)		 Arguments setting
(python.linting.)		 Custom path setting
(python.linting.)
Pylint (default) pylint Enabled pylintEnabled pylintArgs pylintPath
Flake8 flake8 Disabled flake8Enabled flake8Args flake8Path
mypy mypy Disabled mypyEnabled mypyArgs mypyPath
pydocstyle pydocstyle Disabled pydocstyleEnabled pydocstyleArgs pydocstylePath
Pep8 (pycodestyle) pep8 Disabled pep8Enabled pep8Args pep8Path
prospector prospector Disabled prospectorEnabled prospectorArgs prospectorPath
pylama pylama Disabled pylamaEnabled pylamaArgs pylamaPath
bandit bandit Disabled banditEnabled banditArgs banditPath

To select a different linter, use the Python: Select Linter command. You can also edit your settings manually to enable multiple linters. Note, however, that using the Select Linter command overwrites those edits.

Custom arguments are specified in the appropriate arguments setting for each linter. Each top-level element of an argument string that's separated by a space on the command line must be a separate item in the args list. For example:

"python.linting.pylintArgs": ["--reports", "12", "--disable", "I0011"],
"python.linting.flake8Args": ["--ignore=E24,W504", "--verbose"]
"python.linting.pydocstyleArgs": ["--ignore=D400", "--ignore=D4"]

Note that if a top-level element is a single value, as delineated by quotation marks or braces, is still appears as a single item in the list even if the value itself contains spaces.

A custom path is generally unnecessary as the Python extension resolves the path to the linter based on the Python interpreter being used (see Environments). To use a different version of a linter, specify its path in the appropriate custom path setting. For example, if your selected interpreter is a virtual environment but you want to use a linter that's installed in a global environment, then set the appropriate path setting to point to the global environment's linter.

The sections that follow provide additional details for those individual linters linked in the table. In general, custom rules must be specified in a separate file as required by the linter you're using.

Pylint

Pylint messages fall into the categories in the following table with the indicated mapping to VS Code categories. You can change the setting to change the mapping.

Pylint category Description VS Code category mapping Applicable setting
(python.linting.)
Convention (C) Programming standard violation Information (green underline) pylintCategorySeverity.convention
Refactor (R) Bad code smell Hint (light bulbs) pylintCategorySeverity.refactor
Warning (W) Python-specific problems Warning pylintCategorySeverity.warning
Error (E) Likely code bugs Error (red underline) pylintCategorySeverity.error
Fatal (F) An error prevented further Pylint processing Error pylintCategorySeverity.fatal

Default Pylint rules

Python in Visual Studio code is configured by default to use a set of linting rules that are friendly to the largest number of Python developers:

These rules are applied through the following default arguments passed to Pylint:

--disable=all --enable=F,E,unreachable,duplicate-key,unnecessary-semicolon,global-variable-not-assigned,unused-variable,binary-op-exception,bad-format-string,anomalous-backslash-in-string,bad-open-mode

These arguments are passed whenever the python.linting.pylintUseMinimalCheckers is set to true (the default). If you specify a value in pylintArgs or use a Pylint configuration file (see the next section), then pylintUseMinimalCheckers is implicitly set to false.

For the complete list of Pylint messages, see readable-pylint-messages (GitHub).

Command-line arguments and configuration files

See Pylint command-line arguments for general switches. Command-line arguments can be used to load Pylint plugins, such as the plugin for Django:

"python.linting.pylintArgs": ["--load-plugins", "pylint_django"]

Options can also be specified in a pylintrc or .pylintrc options file in the workspace folder, as described on Pylint command line arguments.

To control which Pylint messages are shown, add the following contents to an options file:

[MESSAGES CONTROL]

# 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.
#enable=

# Disable 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).
#disable=

You can easily generate an options file using Pylint itself:

# Using an *nix shell or cmd on Windows
pylint --generate-rcfile > .pylintrc

For PowerShell you have to explictly specify a UTF-8 output encoding:

pylint --generate-rcfile | Out-File -Encoding utf8 .pylintrc

The generated file contains sections for all the Pylint options, along with documentation in the comments.

pydocstyle

Command-line arguments and configuration files

See pydocstyle Command Line Interface for general options. For example, to ignore error D400 (first line should end with a period), add the following line to your settings.json file:

"python.linting.pydocstyleArgs": ["--ignore=D400"]

A code prefix also instructs pydocstyle to ignore specific categories of errors. For example, to ignore all Docstring Content issues (D4XXX errors), add the following line to settings.json:

"python.linting.pydocstyleArgs": ["--ignore=D4"]

More details can be found in the pydocstyle documentation.

Options can also be read from a [pydocstyle] section of any of the following configuration files:

For more information, see Configuration Files.

Message category mapping

The Python extension maps all pydocstyle errors to the Convention (C) category.

Pep8 (pycodestyle)

Command-line arguments and configuration files

See pycodestyle example usage and output for general switches. For example, to ignore error E303 (too many blank lines), add the following line to your settings.json file:

"python.linting.pep8Args": ["--ignore=E303"]

Pep8 options are read from the [pep8] section of a tox.ini or setup.cfg file located in any parent folder of the path(s) being processed. For details, see pycodestyle configuration.

Message category mapping

The Python extension maps pep8 message categories to VS Code categories through the following settings. If desired, change the setting to change the mapping.

Pep8 category Applicable setting
(python.linting.)		 VS Code category mapping
W pep8CategorySeverity.W Warning
E pep8CategorySeverity.E Error

Prospector

Command-line arguments and configuration files

See Prospector Command Line Usage for general options. For example, to set a strictness level of "very high," add the following line to your settings.json file:

"python.linting.prospectorArgs": ["-s", "veryhigh"]

It's common with Prospector to use profiles to configure how Prospector runs. By default, Prospector loads the profile from a .prospector.yaml file in the current folder.

Because Prospector calls other tools, such as Pylint, any configuration files for those tools override tool-specific settings in .prospector.yaml. For example, suppose you specify the following in .prospector.yaml:

pylint:
  disable:
    - too-many-arguments

If you also have a .pylintrc file that enables the too-many-arguments warning, you continue to see the warning from Pylint within VS Code.

Message category mapping

The Python extension maps all Prospector errors and warnings to the Error (E) category.

Flake8

Command-line arguments and configuration files

See Invoking Flake8 for general switches. For example, to ignore error E303 (too many blank lines), use the following setting:

"python.linting.flake8Args": ["--ignore=E303"]

By default, Flake8 ignores E121, E123, E126, E226, E24, and E704.

Flake8 user options are read from the C:\Users\<username>\.flake8 (Windows) or ~/.config/flake8 (macOS/Linux) file.

At the project level, options are read from the [flake8] section of a tox.ini, setup.cfg, or .flake8 file.

For details, see Flake8 configuration.

Message category mapping

The Python extension maps flake8 message categories to VS Code categories through the following settings. If desired, change the setting to change the mapping.

Flake8 category Applicable setting
(python.linting.)		 VS Code category mapping
F flake8CategorySeverity.F Error
E flake8CategorySeverity.E Error
W flake8CategorySeverity.W Warning

mypy

Message category mapping

The Python extension maps mypy message categories to VS Code categories through the following settings. If desired, change the setting to change the mapping.

mypy category Applicable setting
(python.linting.)		 VS Code category mapping
error mypyCategorySeverity.error Error
note mypyCategorySeverity.note Information

Troubleshooting linting

Error message Cause Solution
... unable to import \<module_name> The Python extension is using the wrong version of Pylint. Ensure that the pythonPath setting points to a valid Python installation where Pylint is installed. Alternately, set the python.linting.pylintPath to an appropriate version of Pylint for the Python interpreter being used.
Linting with \<linter> failed ... The path to the Python interpreter is incorrect. Check the pythonPath setting (see Environments).
The linter has not been installed in the current Python environment. Open a command window, navigate to the location of the Python interpreter in the pythonPath setting, and run pip install for the linter.
The path to the linter is incorrect. Ensure that the appropriate python.linting.<linter>Path setting for the linter is correct.
Custom arguments are defined incorrectly. Check the appropriate python.linting.<linter>Args settings, and that the value of the setting is a list of the argument elements that are separated by spaces. For example, "python.linting.pylintPath": "pylint --load-plugins pylint_django" is incorrect. The correct syntax is "python.linting.pylintArgs": ["--load-plugins", "pylint_django"].

Next steps