Contributing to Flake8

There are many ways to contriubte to Flake8, and we encourage them all:

  • contributing bug reports and feature requests
  • contributing documenation (and yes that includes this document)
  • reviewing and triaging bugs and merge requests

Before you go any further, please allow me to reassure you that I do want your contribution. If you think your contribution might not be valuable, I reassure you that any help you can provide is valuable.

Code of Conduct

Flake8 adheres to the Python Code Quality Authority’s Code of Conduct. Any violations of the Code of Conduct should be reported to Ian Cordasco (graffatcolmingov [at] gmail [dot] com).

Setting Up A Development Environment

To contribute to Flake8‘s development, you simply need:

  • Python (one of the versions we support)

  • tox

    We suggest installing this like:

    pip install --user tox


    python<version> -m pip install --user tox
  • your favorite editor

Filing a Bug

When filing a bug against Flake8, please fill out the issue template as it is provided to you by GitLab. If your bug is in reference to one of the checks that Flake8 reports by default, please do not report them to Flake8 unless Flake8 is doing something to prevent the check from running or you have some reason to believe Flake8 is inhibiting the effectiveness of the check.

Please search for closed and open bug reports before opening new ones.

All bug reports about checks should go to their respective projects:

  • Error codes starting with E and W should be reported to pycodestyle.
  • Error codes starting with F should be reported to pyflakes
  • Error codes starting with C should be reported to mccabe

Requesting a New Feature

When requesting a new feature in Flake8, please fill out the issue template. Please also note if there are any existing alternatives to your new feature either via plugins, or combining command-line options. Please provide example use cases. For example, do not ask for a feature like this:

I need feature frobulate for my job.

Instead ask:

I need Flake8 to frobulate these files because my team expects them to frobulated but Flake8 currently does not frobulate them. We tried using --filename but we could not create a pattern that worked.

The more you explain about why you need a feature, the more likely we are to understand your needs and help you to the best of our ability.

Contributing Documentation

To contribute to Flake8‘s documentation, you might want to first read a little about reStructuredText or Sphinx. Flake8 has a guide of best practices when contributing to our documentation. For the most part, you should be fine following the structure and style of the rest of Flake8‘s documentation.

All of Flake8‘s documentation is written in reStructuredText and rendered by Sphinx. The source (reStructuredText) lives in docs/source/. To build the documentation the way our Continuous Integration does, run:

tox -e docs

To view the documentation locally, you can also run:

tox -e serve-docs

You can run the latter in a separate terminal and continuously re-run the documentation generation and refresh the documentation you’re working on.


We lint our documentation just like we lint our code. You should also run:

tox -e linters

After making changes and before pushing them to ensure that they will pass our CI tests.

Contributing Code

Flake8 development happens on GitLab. Code contributions should be submitted there.

Merge requests should:

  • Fix one issue and fix it well

    Fix the issue, but do not include extraneous refactoring or code reformatting. In other words, keep the diff short, but only as short as is necessary to fix the bug appropriately and add sufficient testing around it. Long diffs are fine, so long as everything that it includes is necessary to the purpose of the merge request.

  • Have descriptive titles and descriptions

    Searching old merge requests is made easier when a merge request is well described.

  • Have commits that follow this style:

    Create a short title that is 50 characters long
    Ensure the title and commit message use the imperative voice. The
    commit and you are doing something. Also, please ensure that the
    body of the commit message does not exceed 72 characters.
    The body may have multiple paragraphs as necessary.
    The final line of the body references the issue appropriately.

Reviewing and Triaging Issues and Merge Requests

When reviewing other people’s merge requests and issues, please be especially mindful of how the words you choose can be read by someone else. We strive for professional code reviews that do not insult the contributor’s intelligence or impugn their character. The code review should be focused on the code, it’s effectiveness, and whether it is appropriate for Flake8.

If you have the ability to edit an issue or merge request’s labels, please do so to make search and prioritization easier.

Flake8 uses milestones with both issues and merge requests. This provides direction for other contributors about when an issue or merge request will be delivered.