flake8: Style Linting Command Reference

The long-standing pyflakes + pycodestyle linter.

flake8 combines pyflakes and pycodestyle to catch unused imports, undefined names, and style violations. It remains a common CI lint gate, though ruff is a faster alternative.

Common flags / usage

• flake8 . -- lint the current tree
• --select CODES -- enable only specific checks
• --extend-ignore CODES -- ignore additional checks
• --max-line-length N -- set the line-length limit
• config via setup.cfg, tox.ini, or .flake8

Example

- run: pip install flake8
- run: flake8 --max-line-length=100 src/ tests/

In CI

Keep flake8 settings in setup.cfg or .flake8 so local and CI runs agree. flake8 exits non-zero on any finding, gating the build. Many teams now run ruff check for the same coverage at much higher speed.

Key takeaways

• flake8 catches style issues and simple errors via pyflakes/pycodestyle.
• Configure it in setup.cfg/.flake8 so CI and local match.
• It gates on any finding; ruff is a faster modern alternative.

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