Using Version Control Hooks

Usage with the pre-commit git hooks framework

Flake8 can be included as a hook for pre-commit. The easiest way to get started is to add this configuration to your .pre-commit-config.yaml:

-   repo:
    rev: ''  # pick a git hash / tag to point to
    -   id: flake8

See the pre-commit docs for how to customize this configuration.

Checked-in python files will be passed as positional arguments. flake8 will always lint explicitly passed arguments (flake8 --exclude has no effect). Instead use pre-commit’s exclude: ... regex to exclude files. pre-commit won’t ever pass untracked files to flake8 so excluding .git / .tox / etc. is unnecesary.

-   id: flake8
    exclude: ^testing/(data|examples)/

pre-commit creates an isolated environment for hooks. To use flake8 plugins, use the additional_dependencies setting.

-   id: flake8
    additional_dependencies: [flake8-docstrings]

Built-in Hook Integration


It is strongly suggested to use Flake8 via pre-commit over the built-in hook mechanisms. pre-commit smooths out many of the rough edges of git and is much more battle-tested than the Flake8 hook impementation.

Flake8 can be integrated into your development workflow in many ways. A default installation of Flake8 can install pre-commit hooks for both Git and Mercurial. To install a built-in hook, you can use the flake8 --install-hook command-line option. For example, you can install a git pre-commit hook by running:

flake8 --install-hook git

This will install the pre-commit hook into .git/hooks/. Alternatively, you can install the mercurial commit hook by running

flake8 --install-hook mercurial

Preventing Commits

By default, Flake8 does not prevent you from creating a commit with these hooks. Both hooks can be configured to be strict easily.

Both our Git and Mercurial hooks check for the presence of flake8.strict in each VCS’ config. For example, you might configure this like so:

git config --bool flake8.strict true
hg config flake8.strict true

Checking All Modified Files Currently Tracked


Mercurial does not have the concept of an index or “stage” as best as I understand.

Flake8 aims to make smart choices that keep things fast for users where possible. As a result, the Flake8 Git pre-commit will default to only checking files that have been staged (i.e., added to the index). If, however, you are keen to be lazy and not independenty add files to your git index, you can set flake8.lazy to true (similar to how you would set flake8.strict above) and this will check all tracked files.

This is to support users who often find themselves doing things like:

git commit -a


If you have files you have not yet added to the index, Flake8 will not see these and will not check them for you. You must git-add them first.