Flake8 is a popular lint wrapper for python. Under the hood, it runs three other tools and combines their results:

Run Locally

The mozlint integration of flake8 can be run using mach:

$ mach lint --linter flake8 <file paths>

Alternatively, omit the --linter flake8 and run all configured linters, which will include flake8.


Only directories explicitly whitelisted will have flake8 run against them. To enable flake8 linting in a source directory, it must be added to the include directive in `tools/lint/flake8.lint. If you wish to exclude a subdirectory of an included one, you can add it to the exclude directive.

The default configuration file lives in topsrcdir/.flake8. The default configuration can be overridden for a given subdirectory by creating a new .flake8 file in the subdirectory. Be warned that .flake8 files cannot inherit from one another, so all configuration you wish to keep must be re-defined.


Only .flake8 files that live in a directory that is explicitly included in the include directive will be considered. See bug 1277851 for more details.

For an overview of the supported configuration, see flake8’s documentation.