flake8 can install hooks for Mercurial and Git so that flake8 is run automatically before commits. The commit will fail if there are any flake8 issues.

You can install the hook by issuing this command in the root of your project:

$ flake8 --install-hook

In the case of Git, the hook won’t be installed if a custom pre-commit hook file is already present in the .git/hooks directory.

You can control the behavior of the pre-commit hook using configuration file settings or environment variables:

flake8.complexity or FLAKE8_COMPLEXITY
Any value > 0 enables complexity checking with McCabe. (defaults to 10)
flake8.strict or FLAKE8_STRICT
If True, this causes the commit to fail in case of any errors at all. (defaults to False)
flake8.ignore or FLAKE8_IGNORE
Comma-separated list of errors and warnings to ignore. (defaults to empty)
flake8.lazy or FLAKE8_LAZY
If True, also scans those files not added to the index before commit. (defaults to False)

You can set these either through the git command line

$ git config flake8.complexity 10
$ git config flake8.strict true

Or by directly editing .git/config and adding a section like

    complexity = 10
    strict = true
    lazy = false