Ruff (Rust, by Astral) is a Python linter and formatter that runs 10–100× faster than the tools it replaces — Flake8 (+dozens of plugins), Black, isort, pyupgrade, pydocstyle, bandit and more — behind two commands: ruff check (lint) and ruff format (format). Config lives in pyproject.toml. This sheet targets Ruff 0.16, which enables far more rules by default and adds # ruff: ignore line suppressions.
Verified 2026-08-24 against the official docs at docs.astral.sh/ruff and the astral-sh/ruff repo (Ruff 0.16). Single static binary; the formatter is intentionally Black-compatible.
Two commands do everything: ruff check and ruff format. The rest is choosing rules and suppressing the odd false positive.
Two subcommands: lint and format.
pip install ruff # or: uv tool install ruff★uvx ruff ... to run without installing.ruff check .★ruff format .★ruff format --check to verify without writing (CI).ruff check --diff · ruff format --diffruff check --fix .★ruff check --fix --unsafe-fixes .★ruff check --watch .ruff check --add-noqa .noqa comments for all current findings — a pragmatic way to adopt Ruff on a legacy codebase.Each rule has a code; codes group into categories by the tool they came from.
E / W = pycodestyle · F = Pyflakes · I = isort★B = bugbear · UP = pyupgrade · SIM = simplify · C4 = comprehensions★N = pep8-naming · S = bandit (security) · PT = pytest · D = pydocstyleRUF = Ruff-native · ANN = annotations · PL = pylintE501 = line too long, F401 = unused import.ruff linter # list all rule categories★ruff rule F401 · ruff rule --all★ruff check --statistics .One [tool.ruff] block controls both linter and formatter.
[tool.ruff]
line-length = 88
target-version = "py312"★target-version drives which upgrades (UP) apply. Also ruff.toml standalone.[tool.ruff]
extend-exclude = ["migrations", "build"].gitignore by default; add extra excludes here.ruff check --config "line-length=100" .[tool.ruff.lint]
select = ["E", "F", "I", "B", "UP", "SIM", "C4", "N"]★[tool.ruff.lint]. A solid, opinionated starter set. Use extend-select to add to the defaults instead of replacing.ignore = ["E501"]★E501 (line length) is common when you let the formatter handle wrapping.[tool.ruff.lint.per-file-ignores]
"__init__.py" = ["F401"]
"tests/*" = ["S101"]★__init__, assert in tests.[tool.ruff.lint.isort]
known-first-party = ["myapp"]The Black-compatible half.
ruff format .★[tool.ruff.format]
quote-style = "double"
indent-style = "space"★docstring-code-format = true formats code blocks in docstrings; 0.16 also formats code in Markdown.select = ["I"] # let the LINTER sort imports; formatter won't★I), not part of format. Enable I and run check --fix to sort.enable I, ignore E501 to avoid fightingtipE501) in lint so the two don't disagree about wrapping.Silence false positives and wire into your workflow.
x = bad() # noqa: E501★# noqa silences all — prefer naming the codes.# ruff: ignore[E501] # 0.16: like noqa, incl. on the preceding line# ruff: noqa # at top of file = ignore this file entirely
# ruff: noqa: F401 # file-level, specific rule★ruff check --fix --exit-zero · --output-format=github# .pre-commit-config.yaml
- repo: https://github.com/astral-sh/ruff-pre-commit
hooks: [{id: ruff-check, args: [--fix]}, {id: ruff-format}]★ruff server # built-in language server (LSP)ruff check --output-format=json | ...select replaces, extend-select addsselect defines the entire active set. To keep defaults and add more, use extend-select.lint config under [tool.ruff.lint]select/ignore live under [tool.ruff.lint], not [tool.ruff]. Old top-level keys are deprecated.import sorting is a lint rule, not formatruff format won't sort imports — enable I and run check --fix (or the pre-commit lint hook).Ruff is not a type checkerunsafe fixes can change behavior--unsafe-fixes may alter semantics — review the diff and rely on tests.