Ruff

Ruff replaces Pylint, isort, and black with a single pass that runs 10-100x faster. It's a Python linter and formatter written in Rust that replaces five or six tools at once. The speed difference is not subtle. Large codebases that took 30 seconds now take under a second.

Everything is free under MIT. No paid tier, no cloud, no account. Ruff is from Astral (same team as uv), and like uv, there's no monetization yet. Every rule from flake8, isort, pycodestyle, pyflakes, and more is reimplemented and included.

The catch: Ruff doesn't support custom plugins the way flake8 does. If your team relies on custom flake8 plugins for domain-specific rules, you can't migrate those yet. And like uv, Astral's long-term business model is undefined. You're betting on a VC-funded company's goodwill. The Apache/MIT license protects you, but active maintenance isn't guaranteed forever.