ruff 0.0.127

An extremely fast Python linter, written in Rust.

Ruff

An extremely fast Python linter, written in Rust.

Linting the CPython codebase from scratch.

• ⚡️ 10-100x faster than existing linters
• 🐍 Installable via pip
• 🤝 Python 3.10 compatibility
• 🛠️ pyproject.toml support
• 📦 Built-in caching, to avoid re-analyzing unchanged files
• 🔧 --fix support, for automatic error correction (e.g., automatically remove unused imports)
• 👀 --watch support, for continuous file monitoring
• ⚖️ Near-parity with the built-in Flake8 rule set
• 🔌 Native re-implementations of popular Flake8 plugins, like flake8-docstrings (pydocstyle)

Ruff aims to be orders of magnitude faster than alternative tools while integrating more functionality behind a single, common interface. Ruff can be used to replace Flake8 (plus a variety of plugins), isort, pydocstyle, yesqa, and even a subset of pyupgrade and autoflake all while executing tens or hundreds of times faster than any individual tool.

(Coming from Flake8? Try flake8-to-ruff to automatically convert your existing configuration.)

Ruff is actively developed and used in major open-source projects like FastAPI, Zulip, pydantic, and Saleor.

Read the launch blog post.

Table of Contents

1. Installation and Usage
2. Configuration
3. Supported Rules
   1. Pyflakes (F)
   2. pycodestyle (E)
   3. isort (I)
   4. pydocstyle (D)
   5. pyupgrade (U)
   6. pep8-naming (N)
   7. flake8-bandit (S)
   8. flake8-comprehensions (C)
   9. flake8-bugbear (B)
   10. flake8-builtins (A)
   11. flake8-tidy-imports (I25)
   12. flake8-print (T)
   13. flake8-quotes (Q)
   14. flake8-annotations (ANN)
   15. flake8-2020 (YTT)
   16. flake8-blind-except (BLE)
   17. flake8-boolean-trap (FBT)
   18. mccabe (C90)
   19. Ruff-specific rules (RUF)
   20. Meta rules (M)
4. Editor Integrations
5. FAQ
6. Development
7. Releases
8. Benchmarks
9. License
10. Contributing

Installation and Usage

Installation

Available as ruff on PyPI:

pip install ruff

Usage

To run Ruff, try any of the following:

ruff path/to/code/to/check.py
ruff path/to/code/
ruff path/to/code/*.py

You can run Ruff in --watch mode to automatically re-run on-change:

ruff path/to/code/ --watch

Ruff also works with pre-commit:

repos:
  - repo: https://github.com/charliermarsh/ruff-pre-commit
    rev: v0.0.116
    hooks:
      - id: ruff

Note: prior to v0.0.86, ruff-pre-commit used lint (rather than ruff) as the hook ID.

Configuration

Ruff is configurable both via pyproject.toml and the command line. If left unspecified, the default configuration is equivalent to:

[tool.ruff]
line-length = 88

# Enable Flake's "E" and "F" codes by default.
select = ["E", "F"]
ignore = []

# Exclude a variety of commonly ignored directories.
exclude = [
    ".bzr",
    ".direnv",
    ".eggs",
    ".git",
    ".hg",
    ".mypy_cache",
    ".nox",
    ".pants.d",
    ".ruff_cache",
    ".svn",
    ".tox",
    ".venv",
    "__pypackages__",
    "_build",
    "buck-out",
    "build",
    "dist",
    "node_modules",
    "venv",
]
per-file-ignores = {}

# Allow unused variables when underscore-prefixed.
dummy-variable-rgx = "^(_+|(_+[a-zA-Z0-9_]*[a-zA-Z0-9]+?))$"

# Assume Python 3.10.
target-version = "py310"

As an example, the following would configure Ruff to (1) avoid checking for line-length violations (E501) and (2) ignore unused import rules in __init__.py files:

[tool.ruff]
select = ["E", "F"]

# Never enforce `E501`.
ignore = ["E501"]

# Ignore `F401` violations in any `__init__.py` file, and in `path/to/file.py`.
per-file-ignores = {"__init__.py" = ["F401"], "path/to/file.py" = ["F401"]}

Plugin configurations should be expressed as subsections, e.g.:

[tool.ruff]
# Add "Q" to the list of enabled codes.
select = ["E", "F", "Q"]

[tool.ruff.flake8-quotes]
docstring-quotes = "double"

Alternatively, common configuration settings can be provided via the command-line:

ruff path/to/code/ --select F401 --select F403

See ruff --help for more:

ruff: An extremely fast Python linter.

Usage: ruff [OPTIONS] <FILES>...

Arguments:
  <FILES>...

Options:
      --config <CONFIG>
          Path to the `pyproject.toml` file to use for configuration
  -v, --verbose
          Enable verbose logging
  -q, --quiet
          Only log errors
  -s, --silent
          Disable all logging (but still exit with status code "1" upon detecting errors)
  -e, --exit-zero
          Exit with status code "0", even upon detecting errors
  -w, --watch
          Run in watch mode by re-running whenever files change
      --fix
          Attempt to automatically fix lint errors
  -n, --no-cache
          Disable cache reads
      --select <SELECT>
          List of error codes to enable
      --extend-select <EXTEND_SELECT>
          Like --select, but adds additional error codes on top of the selected ones
      --ignore <IGNORE>
          List of error codes to ignore
      --extend-ignore <EXTEND_IGNORE>
          Like --ignore, but adds additional error codes on top of the ignored ones
      --exclude <EXCLUDE>
          List of paths, used to exclude files and/or directories from checks
      --extend-exclude <EXTEND_EXCLUDE>
          Like --exclude, but adds additional files and directories on top of the excluded ones
      --per-file-ignores <PER_FILE_IGNORES>
          List of mappings from file pattern to code to exclude
      --format <FORMAT>
          Output serialization format for error messages [default: text] [possible values: text, json]
      --show-files
          See the files ruff will be run against with the current settings
      --show-settings
          See ruff's settings
      --add-noqa
          Enable automatic additions of noqa directives to failing lines
      --dummy-variable-rgx <DUMMY_VARIABLE_RGX>
          Regular expression matching the name of dummy variables
      --target-version <TARGET_VERSION>
          The minimum Python version that should be supported
      --line-length <LINE_LENGTH>
          Set the line-length for length-associated checks and automatic formatting
      --max-complexity <MAX_COMPLEXITY>
          Set the maximum cyclomatic complexity for complexity-associated checks
      --stdin-filename <STDIN_FILENAME>
          The name of the file when passing it through stdin
  -h, --help
          Print help information
  -V, --version
          Print version information

Excluding files

Exclusions are based on globs, and can be either:

• Single-path patterns, like .mypy_cache (to exclude any directory named .mypy_cache in the tree), foo.py (to exclude any file named foo.py), or foo_*.py (to exclude any file matching foo_*.py ).
• Relative patterns, like directory/foo.py (to exclude that specific file) or directory/*.py (to exclude any Python files in directory). Note that these paths are relative to the project root (e.g., the directory containing your pyproject.toml).

Ignoring errors

To omit a lint check entirely, add it to the "ignore" list via --ignore or --extend-ignore, either on the command-line or in your project.toml file.

To ignore an error in-line, Ruff uses a noqa system similar to Flake8. To ignore an individual error, add # noqa: {code} to the end of the line, like so:

# Ignore F841.
x = 1  # noqa: F841

# Ignore E741 and F841.
i = 1  # noqa: E741, F841

# Ignore _all_ errors.
x = 1  # noqa

Note that, for multi-line strings, the noqa directive should come at the end of the string, and will apply to the entire body, like so:

"""Lorem ipsum dolor sit amet.

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
"""  # noqa: E501

Ruff supports several workflows to aid in noqa management.

First, Ruff provides a special error code, M001, to enforce that your noqa directives are "valid", in that the errors they say they ignore are actually being triggered on that line (and thus suppressed). You can run ruff /path/to/file.py --extend-select M001 to flag unused noqa directives.

Second, Ruff can automatically remove unused noqa directives via its autofix functionality. You can run ruff /path/to/file.py --extend-select M001 --fix to automatically remove unused noqa directives.

Third, Ruff can automatically add noqa directives to all failing lines. This is useful when migrating a new codebase to Ruff. You can run ruff /path/to/file.py --add-noqa to automatically add noqa directives to all failing lines, with the appropriate error codes.

Supported Rules

Regardless of the rule's origin, Ruff re-implements every rule in Rust as a first-party feature.

By default, Ruff enables all E and F error codes, which correspond to those built-in to Flake8.

The 🛠 emoji indicates that a rule is automatically fixable by the --fix command-line option.

Pyflakes

For more, see Pyflakes on PyPI.

Code	Name	Message	Fix
F401	UnusedImport	... imported but unused	🛠
F402	ImportShadowedByLoopVar	Import ... from line 1 shadowed by loop variable
F403	ImportStarUsed	from ... import * used; unable to detect undefined names
F404	LateFutureImport	from __future__ imports must occur at the beginning of the file
F405	ImportStarUsage	... may be undefined, or defined from star imports: ...
F406	ImportStarNotPermitted	from ... import * only allowed at module level
F407	FutureFeatureNotDefined	Future feature ... is not defined
F541	FStringMissingPlaceholders	f-string without any placeholders
F601	MultiValueRepeatedKeyLiteral	Dictionary key literal repeated
F602	MultiValueRepeatedKeyVariable	Dictionary key ... repeated
F621	ExpressionsInStarAssignment	Too many expressions in star-unpacking assignment
F622	TwoStarredExpressions	Two starred expressions in assignment
F631	AssertTuple	Assert test is a non-empty tuple, which is always True
F632	IsLiteral	Use == and != to compare constant literals	🛠
F633	InvalidPrintSyntax	Use of >> is invalid with print function
F634	IfTuple	If test is a tuple, which is always True
F701	BreakOutsideLoop	break outside loop
F702	ContinueOutsideLoop	continue not properly in loop
F704	YieldOutsideFunction	yield or yield from statement outside of a function
F706	ReturnOutsideFunction	return statement outside of a function/method
F707	DefaultExceptNotLast	An except block as not the last exception handler
F722	ForwardAnnotationSyntaxError	Syntax error in forward annotation: ...
F821	UndefinedName	Undefined name ...
F822	UndefinedExport	Undefined name ... in __all__
F823	UndefinedLocal	Local variable ... referenced before assignment
F831	DuplicateArgumentName	Duplicate argument name in function definition
F841	UnusedVariable	Local variable ... is assigned to but never used
F901	RaiseNotImplemented	raise NotImplemented should be raise NotImplementedError	🛠

pycodestyle

For more, see pycodestyle on PyPI.

Code	Name	Message	Fix
E402	ModuleImportNotAtTopOfFile	Module level import not at top of file
E501	LineTooLong	Line too long (89 > 88 characters)
E711	NoneComparison	Comparison to None should be cond is None	🛠
E712	TrueFalseComparison	Comparison to True should be cond is True	🛠
E713	NotInTest	Test for membership should be not in	🛠
E714	NotIsTest	Test for object identity should be is not	🛠
E721	TypeComparison	Do not compare types, use isinstance()
E722	DoNotUseBareExcept	Do not use bare except
E731	DoNotAssignLambda	Do not assign a lambda expression, use a def
E741	AmbiguousVariableName	Ambiguous variable name: ...
E742	AmbiguousClassName	Ambiguous class name: ...
E743	AmbiguousFunctionName	Ambiguous function name: ...
E902	IOError	IOError: ...
E999	SyntaxError	SyntaxError: ...
W292	NoNewLineAtEndOfFile	No newline at end of file
W605	InvalidEscapeSequence	Invalid escape sequence: '\c'

isort

For more, see isort on PyPI.

Code	Name	Message	Fix
I001	UnsortedImports	Import block is un-sorted or un-formatted	🛠

pydocstyle

For more, see pydocstyle on PyPI.

Code	Name	Message	Fix
D100	PublicModule	Missing docstring in public module
D101	PublicClass	Missing docstring in public class
D102	PublicMethod	Missing docstring in public method
D103	PublicFunction	Missing docstring in public function
D104	PublicPackage	Missing docstring in public package
D105	MagicMethod	Missing docstring in magic method
D106	PublicNestedClass	Missing docstring in public nested class
D107	PublicInit	Missing docstring in __init__
D200	FitsOnOneLine	One-line docstring should fit on one line
D201	NoBlankLineBeforeFunction	No blank lines allowed before function docstring (found 1)	🛠
D202	NoBlankLineAfterFunction	No blank lines allowed after function docstring (found 1)	🛠
D203	OneBlankLineBeforeClass	1 blank line required before class docstring	🛠
D204	OneBlankLineAfterClass	1 blank line required after class docstring	🛠
D205	BlankLineAfterSummary	1 blank line required between summary line and description	🛠
D206	IndentWithSpaces	Docstring should be indented with spaces, not tabs
D207	NoUnderIndentation	Docstring is under-indented	🛠
D208	NoOverIndentation	Docstring is over-indented	🛠
D209	NewLineAfterLastParagraph	Multi-line docstring closing quotes should be on a separate line	🛠
D210	NoSurroundingWhitespace	No whitespaces allowed surrounding docstring text	🛠
D211	NoBlankLineBeforeClass	No blank lines allowed before class docstring	🛠
D212	MultiLineSummaryFirstLine	Multi-line docstring summary should start at the first line
D213	MultiLineSummarySecondLine	Multi-line docstring summary should start at the second line
D214	SectionNotOverIndented	Section is over-indented ("Returns")	🛠
D215	SectionUnderlineNotOverIndented	Section underline is over-indented ("Returns")	🛠
D300	UsesTripleQuotes	Use """triple double quotes"""
D400	EndsInPeriod	First line should end with a period
D402	NoSignature	First line should not be the function's signature
D403	FirstLineCapitalized	First word of the first line should be properly capitalized
D404	NoThisPrefix	First word of the docstring should not be "This"
D405	CapitalizeSectionName	Section name should be properly capitalized ("returns")	🛠
D406	NewLineAfterSectionName	Section name should end with a newline ("Returns")	🛠
D407	DashedUnderlineAfterSection	Missing dashed underline after section ("Returns")	🛠
D408	SectionUnderlineAfterName	Section underline should be in the line following the section's name ("Returns")	🛠
D409	SectionUnderlineMatchesSectionLength	Section underline should match the length of its name ("Returns")	🛠
D410	BlankLineAfterSection	Missing blank line after section ("Returns")	🛠
D411	BlankLineBeforeSection	Missing blank line before section ("Returns")	🛠
D412	NoBlankLinesBetweenHeaderAndContent	No blank lines allowed between a section header and its content ("Returns")	🛠
D413	BlankLineAfterLastSection	Missing blank line after last section ("Returns")	🛠
D414	NonEmptySection	Section has no content ("Returns")
D415	EndsInPunctuation	First line should end with a period, question mark, or exclamation point
D416	SectionNameEndsInColon	Section name should end with a colon ("Returns")	🛠
D417	DocumentAllArguments	Missing argument descriptions in the docstring: x, y
D418	SkipDocstring	Function decorated with @overload shouldn't contain a docstring
D419	NonEmpty	Docstring is empty

pyupgrade

For more, see pyupgrade on PyPI.

Code	Name	Message	Fix
U001	UselessMetaclassType	__metaclass__ = type is implied	🛠
U003	TypeOfPrimitive	Use str instead of type(...)	🛠
U004	UselessObjectInheritance	Class ... inherits from object	🛠
U005	DeprecatedUnittestAlias	assertEquals is deprecated, use assertEqual instead	🛠
U006	UsePEP585Annotation	Use list instead of List for type annotations	🛠
U007	UsePEP604Annotation	Use X | Y for type annotations	🛠
U008	SuperCallWithParameters	Use super() instead of super(__class__, self)	🛠
U009	PEP3120UnnecessaryCodingComment	UTF-8 encoding declaration is unnecessary	🛠
U010	UnnecessaryFutureImport	Unnecessary __future__ import ... for target Python version	🛠
U011	UnnecessaryLRUCacheParams	Unnecessary parameters to functools.lru_cache	🛠
U012	UnnecessaryEncodeUTF8	Unnecessary call to encode as UTF-8	🛠
U013	ConvertTypedDictFunctionalToClass	Convert TypedDict functional syntax to class syntax	🛠

pep8-naming

For more, see pep8-naming on PyPI.

Code	Name	Message	Fix
N801	InvalidClassName	Class name ... should use CapWords convention
N802	InvalidFunctionName	Function name ... should be lowercase
N803	InvalidArgumentName	Argument name ... should be lowercase
N804	InvalidFirstArgumentNameForClassMethod	First argument of a class method should be named cls
N805	InvalidFirstArgumentNameForMethod	First argument of a method should be named self
N806	NonLowercaseVariableInFunction	Variable ... in function should be lowercase
N807	DunderFunctionName	Function name should not start and end with __
N811	ConstantImportedAsNonConstant	Constant ... imported as non-constant ...
N812	LowercaseImportedAsNonLowercase	Lowercase ... imported as non-lowercase ...
N813	CamelcaseImportedAsLowercase	Camelcase ... imported as lowercase ...
N814	CamelcaseImportedAsConstant	Camelcase ... imported as constant ...
N815	MixedCaseVariableInClassScope	Variable mixedCase in class scope should not be mixedCase
N816	MixedCaseVariableInGlobalScope	Variable mixedCase in global scope should not be mixedCase
N817	CamelcaseImportedAsAcronym	Camelcase ... imported as acronym ...
N818	ErrorSuffixOnExceptionName	Exception name ... should be named with an Error suffix

flake8-bandit

For more, see flake8-bandit on PyPI.

Code	Name	Message	Fix
S101	AssertUsed	Use of assert detected
S102	ExecUsed	Use of exec detected
S104	HardcodedBindAllInterfaces	Possible binding to all interfaces
S105	HardcodedPasswordString	Possible hardcoded password: "..."
S106	HardcodedPasswordFuncArg	Possible hardcoded password: "..."
S107	HardcodedPasswordDefault	Possible hardcoded password: "..."

flake8-comprehensions

For more, see flake8-comprehensions on PyPI.

Code	Name	Message	Fix
C400	UnnecessaryGeneratorList	Unnecessary generator (rewrite as a list comprehension)	🛠
C401	UnnecessaryGeneratorSet	Unnecessary generator (rewrite as a set comprehension)	🛠
C402	UnnecessaryGeneratorDict	Unnecessary generator (rewrite as a dict comprehension)	🛠
C403	UnnecessaryListComprehensionSet	Unnecessary list comprehension (rewrite as a set comprehension)	🛠
C404	UnnecessaryListComprehensionDict	Unnecessary list comprehension (rewrite as a dict comprehension)	🛠
C405	UnnecessaryLiteralSet	Unnecessary (list|tuple) literal (rewrite as a set literal)	🛠
C406	UnnecessaryLiteralDict	Unnecessary (list|tuple) literal (rewrite as a dict literal)	🛠
C408	UnnecessaryCollectionCall	Unnecessary (dict|list|tuple) call (rewrite as a literal)	🛠
C409	UnnecessaryLiteralWithinTupleCall	Unnecessary (list|tuple) literal passed to tuple() (remove the outer call to tuple())	🛠
C410	UnnecessaryLiteralWithinListCall	Unnecessary (list|tuple) literal passed to list() (rewrite as a list literal)	🛠
C411	UnnecessaryListCall	Unnecessary list call (remove the outer call to list())	🛠
C413	UnnecessaryCallAroundSorted	Unnecessary (list|reversed) call around sorted()
C414	UnnecessaryDoubleCastOrProcess	Unnecessary (list|reversed|set|sorted|tuple) call within (list|set|sorted|tuple)()
C415	UnnecessarySubscriptReversal	Unnecessary subscript reversal of iterable within (reversed|set|sorted)()
C416	UnnecessaryComprehension	Unnecessary (list|set) comprehension (rewrite using (list|set)())	🛠
C417	UnnecessaryMap	Unnecessary map usage (rewrite using a (list|set|dict) comprehension)

flake8-boolean-trap

For more, see flake8-boolean-trap on PyPI.

Code	Name	Message	Fix
FBT001	BooleanPositionalArgInFunctionDefinition	Boolean positional arg in function definition
FBT002	BooleanDefaultValueInFunctionDefinition	Boolean default value in function definition
FBT003	BooleanPositionalValueInFunctionCall	Boolean positional value in function call

flake8-bugbear

For more, see flake8-bugbear on PyPI.

Code	Name	Message	Fix
B002	UnaryPrefixIncrement	Python does not support the unary prefix increment
B003	AssignmentToOsEnviron	Assigning to os.environ doesn't clear the environment
B004	UnreliableCallableCheck	Using hasattr(x, '__call__') to test if x is callable is unreliable. Use callable(x) for consistent results.
B005	StripWithMultiCharacters	Using .strip() with multi-character strings is misleading the reader
B006	MutableArgumentDefault	Do not use mutable data structures for argument defaults
B007	UnusedLoopControlVariable	Loop control variable i not used within the loop body	🛠
B008	FunctionCallArgumentDefault	Do not perform function call in argument defaults
B009	GetAttrWithConstant	Do not call getattr with a constant attribute value. It is not any safer than normal property access.	🛠
B010	SetAttrWithConstant	Do not call setattr with a constant attribute value. It is not any safer than normal property access.
B011	DoNotAssertFalse	Do not assert False (python -O removes these calls), raise AssertionError()	🛠
B012	JumpStatementInFinally	return/continue/break inside finally blocks cause exceptions to be silenced
B013	RedundantTupleInExceptionHandler	A length-one tuple literal is redundant. Write except ValueError instead of except (ValueError,).
B014	DuplicateHandlerException	Exception handler with duplicate exception: ValueError	🛠
B015	UselessComparison	Pointless comparison. This comparison does nothing but waste CPU instructions. Either prepend assert or remove it.
B016	CannotRaiseLiteral	Cannot raise a literal. Did you intend to return it or raise an Exception?
B017	NoAssertRaisesException	assertRaises(Exception) should be considered evil
B018	UselessExpression	Found useless expression. Either assign it to a variable or remove it.
B019	CachedInstanceMethod	Use of functools.lru_cache or functools.cache on methods can lead to memory leaks
B020	LoopVariableOverridesIterator	Loop control variable ... overrides iterable it iterates
B021	FStringDocstring	f-string used as docstring. This will be interpreted by python as a joined string rather than a docstring.
B022	UselessContextlibSuppress	No arguments passed to contextlib.suppress. No exceptions will be suppressed and therefore this context manager is redundant
B024	AbstractBaseClassWithoutAbstractMethod	... is an abstract base class, but it has no abstract methods
B025	DuplicateTryBlockException	try-except block with duplicate exception Exception
B026	StarArgUnpackingAfterKeywordArg	Star-arg unpacking after a keyword argument is strongly discouraged
B027	EmptyMethodWithoutAbstractDecorator	... is an empty method in an abstract base class, but has no abstract decorator

flake8-builtins

For more, see flake8-builtins on PyPI.

Code	Name	Message	Fix
A001	BuiltinVariableShadowing	Variable ... is shadowing a python builtin
A002	BuiltinArgumentShadowing	Argument ... is shadowing a python builtin
A003	BuiltinAttributeShadowing	Class attribute ... is shadowing a python builtin

flake8-tidy-imports

For more, see flake8-tidy-imports on PyPI.

Code	Name	Message	Fix
I252	BannedRelativeImport	Relative imports are banned

flake8-print

For more, see flake8-print on PyPI.

Code	Name	Message	Fix
T201	PrintFound	print found	🛠
T203	PPrintFound	pprint found	🛠

flake8-quotes

For more, see flake8-quotes on PyPI.

Code	Name	Message	Fix
Q000	BadQuotesInlineString	Single quotes found but double quotes preferred
Q001	BadQuotesMultilineString	Single quote multiline found but double quotes preferred
Q002	BadQuotesDocstring	Single quote docstring found but double quotes preferred
Q003	AvoidQuoteEscape	Change outer quotes to avoid escaping inner quotes

flake8-annotations

For more, see flake8-annotations on PyPI.

Code	Name	Message	Fix
ANN001	MissingTypeFunctionArgument	Missing type annotation for function argument ...
ANN002	MissingTypeArgs	Missing type annotation for *...
ANN003	MissingTypeKwargs	Missing type annotation for **...
ANN101	MissingTypeSelf	Missing type annotation for ... in method
ANN102	MissingTypeCls	Missing type annotation for ... in classmethod
ANN201	MissingReturnTypePublicFunction	Missing return type annotation for public function ...
ANN202	MissingReturnTypePrivateFunction	Missing return type annotation for private function ...
ANN204	MissingReturnTypeMagicMethod	Missing return type annotation for magic method ...
ANN205	MissingReturnTypeStaticMethod	Missing return type annotation for staticmethod ...
ANN206	MissingReturnTypeClassMethod	Missing return type annotation for classmethod ...
ANN401	DynamicallyTypedExpression	Dynamically typed expressions (typing.Any) are disallowed in ...

flake8-2020

For more, see flake8-2020 on PyPI.

Code	Name	Message	Fix
YTT101	SysVersionSlice3Referenced	sys.version[:3] referenced (python3.10), use sys.version_info
YTT102	SysVersion2Referenced	sys.version[2] referenced (python3.10), use sys.version_info
YTT103	SysVersionCmpStr3	sys.version compared to string (python3.10), use sys.version_info
YTT201	SysVersionInfo0Eq3Referenced	sys.version_info[0] == 3 referenced (python4), use >=
YTT202	SixPY3Referenced	six.PY3 referenced (python4), use not six.PY2
YTT203	SysVersionInfo1CmpInt	sys.version_info[1] compared to integer (python4), compare sys.version_info to tuple
YTT204	SysVersionInfoMinorCmpInt	sys.version_info.minor compared to integer (python4), compare sys.version_info to tuple
YTT301	SysVersion0Referenced	sys.version[0] referenced (python10), use sys.version_info
YTT302	SysVersionCmpStr10	sys.version compared to string (python10), use sys.version_info
YTT303	SysVersionSlice1Referenced	sys.version[:1] referenced (python10), use sys.version_info

flake8-blind-except

For more, see flake8-blind-except on PyPI.

Code	Name	Message	Fix
BLE001	BlindExcept	Blind except Exception: statement

mccabe

For more, see mccabe on PyPI.

Code	Name	Message	Fix
C901	FunctionIsTooComplex	... is too complex (10)

Ruff-specific rules

Code	Name	Message	Fix
RUF001	AmbiguousUnicodeCharacterString	String contains ambiguous unicode character '𝐁' (did you mean 'B'?)	🛠
RUF002	AmbiguousUnicodeCharacterDocstring	Docstring contains ambiguous unicode character '𝐁' (did you mean 'B'?)	🛠
RUF003	AmbiguousUnicodeCharacterComment	Comment contains ambiguous unicode character '𝐁' (did you mean 'B'?)

Meta rules

Code	Name	Message	Fix
M001	UnusedNOQA	Unused noqa directive	🛠

Editor Integrations

VS Code (Official)

Download the Ruff VS Code extension.

PyCharm

Ruff can be installed as an External Tool in PyCharm. Open the Preferences pane, then navigate to "Tools", then "External Tools". From there, add a new tool with the following configuration:

Ruff should then appear as a runnable action:

Vim & Neovim (Unofficial)

Ruff is available as part of the coc-pyright extension for coc.nvim.

Ruff can also be integrated via efm in just a few lines.

tools:
  python-ruff: &python-ruff
    lint-command: 'ruff --config ~/myconfigs/linters/ruff.toml --quiet ${INPUT}'
    lint-stdin: true
    lint-formats:
      - '%f:%l:%c: %m'
    format-command: 'ruff --stdin-filename ${INPUT} --config ~/myconfigs/linters/ruff.toml --fix --exit-zero --quiet -'
    format-stdin: true

For neovim users using null-ls, Ruff is already integrated.

local null_ls = require("null-ls")
local methods = require("null-ls.methods")
local helpers = require("null-ls.helpers")

local function ruff_fix()
    return helpers.make_builtin({
        name = "ruff",
        meta = {
            url = "https://github.com/charliermarsh/ruff/",
            description = "An extremely fast Python linter, written in Rust.",
        },
        method = methods.internal.FORMATTING,
        filetypes = { "python" },
        generator_opts = {
            command = "ruff",
            args = { "--fix", "-e", "-n", "--stdin-filename", "$FILENAME", "-" },
            to_stdin = true
        },
        factory = helpers.formatter_factory
    })
end

null_ls.setup({
    sources = {
        ruff_fix(),
        null_ls.builtins.diagnostics.ruff,
    }
})

Language Server Protocol (Unofficial)

ruffd is a Rust-based language server for Ruff that implements the Language Server Protocol (LSP).

GitHub Actions

GitHub Actions has everything you need to run Ruff out-of-the-box:

name: CI
on: push
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Install Python
        uses: actions/setup-python@v4
        with:
          python-version: "3.10"
      - name: Install dependencies
        run: |
          python -m pip install --upgrade pip
          pip install ruff
      - name: Run Ruff
        run: ruff .

FAQ

Is Ruff compatible with Black?

Yes. Ruff is compatible with Black out-of-the-box, as long as the line-length setting is consistent between the two.

As a project, Ruff is designed to be used alongside Black and, as such, will defer implementing stylistic lint rules that are obviated by autoformatting.

How does Ruff compare to Flake8?

(Coming from Flake8? Try flake8-to-ruff to automatically convert your existing configuration.)

Ruff can be used as a (near) drop-in replacement for Flake8 when used (1) without or with a small number of plugins, (2) alongside Black, and (3) on Python 3 code.

Under those conditions Ruff is missing 14 rules related to string .format calls, 1 rule related to docstring parsing, and 1 rule related to redefined variables.

Ruff re-implements some of the most popular Flake8 plugins and related code quality tools natively, including:

• pydocstyle
• pep8-naming
• yesqa
• flake8-docstrings
• flake8-builtins
• flake8-super
• flake8-tidy-imports (1/3)
• flake8-print
• flake8-quotes
• flake8-annotations
• flake8-comprehensions
• flake8-bandit (6/40)
• flake8-bugbear (25/32)
• flake8-2020
• flake8-blind-except
• flake8-boolean-trap
• mccabe
• isort
• pyupgrade (14/33)
• autoflake (1/7)

Beyond rule-set parity, Ruff suffers from the following limitations vis-à-vis Flake8:

1. Ruff does not yet support a few Python 3.9 and 3.10 language features, including structural pattern matching and parenthesized context managers.
2. Flake8 has a plugin architecture and supports writing custom lint rules. (To date, popular Flake8 plugins have been re-implemented within Ruff directly.)

Which tools does Ruff replace?

Today, Ruff can be used to replace Flake8 when used with any of the following plugins:

• pydocstyle
• pep8-naming
• flake8-docstrings
• flake8-builtins
• flake8-super
• flake8-tidy-imports (1/3)
• flake8-print
• flake8-quotes
• flake8-annotations
• flake8-bandit (6/40)
• flake8-comprehensions
• flake8-bugbear (26/32)
• flake8-2020
• flake8-blind-except
• flake8-boolean-trap
• mccabe

Ruff can also replace isort, yesqa, and a subset of the rules implemented in pyupgrade (14/33).

If you're looking to use Ruff, but rely on an unsupported Flake8 plugin, free to file an Issue.

Do I need to install Rust to use Ruff?

Nope! Ruff is available as ruff on PyPI:

pip install ruff

Ruff ships with wheels for all major platforms, which enables pip to install Ruff without relying on Rust at all.

Can I write my own plugins for Ruff?

Ruff does not yet support third-party plugins, though a plugin system is within-scope for the project. See #283 for more.

How does Ruff's import sorting compare to isort?

Ruff's import sorting is intended to be nearly equivalent to isort when used profile = "black". (There are some minor differences in how Ruff and isort break ties between similar imports.)

Like isort, Ruff's import sorting is compatible with Black.

Ruff is less configurable than isort, but supports the known-first-party, known-third-party, extra-standard-library, and src settings, like so:

[tool.ruff]
select = [
    # Pyflakes
    "F",
    # Pycodestyle
    "E",
    "W",
    # isort
    "I"
]
src = ["src", "tests"]

[tool.ruff.isort]
known-first-party = ["my_module1", "my_module2"]

Does Ruff support NumPy- or Google-style docstrings?

Yes! To enable a specific docstring convention, start by enabling all pydocstyle error codes, and then selectively disabling based on your preferred convention.

For example, if you're coming from flake8-docstrings, the following configuration is equivalent to --docstring-convention=numpy:

[tool.ruff]
extend-select = ["D"]
extend-ignore = [
    "D107",
    "D203",
    "D212",
    "D213",
    "D402",
    "D413",
    "D415",
    "D416",
    "D417",
]

Similarly, the following is equivalent to --docstring-convention=google:

[tool.ruff]
extend-select = ["D"]
extend-ignore = [
    "D203",
    "D204",
    "D213",
    "D215",
    "D400",
    "D404",
    "D406",
    "D407",
    "D408",
    "D409",
    "D413",
]

Similarly, the following is equivalent to --docstring-convention=pep8:

[tool.ruff]
extend-select = ["D"]
extend-ignore = [
    "D203",
    "D212",
    "D213",
    "D214",
    "D215",
    "D404",
    "D405",
    "D406",
    "D407",
    "D408",
    "D409",
    "D410",
    "D411",
    "D413",
    "D415",
    "D416",
    "D417",
]

Development

Ruff is written in Rust (1.65.0). You'll need to install the Rust toolchain for development.

Assuming you have cargo installed, you can run:

cargo run resources/test/fixtures

For development, we use nightly Rust:

cargo +nightly fmt
cargo +nightly clippy
cargo +nightly test

Releases

Ruff is distributed on PyPI, and published via maturin.

See: .github/workflows/release.yaml.

Benchmarks

First, clone CPython. It's a large and diverse Python codebase, which makes it a good target for benchmarking.

git clone --branch 3.10 https://github.com/python/cpython.git resources/test/cpython

Add this pyproject.toml to the CPython directory:

[tool.ruff]
line-length = 88
extend-exclude = [
    "Lib/lib2to3/tests/data/bom.py",
    "Lib/lib2to3/tests/data/crlf.py",
    "Lib/lib2to3/tests/data/different_encoding.py",
    "Lib/lib2to3/tests/data/false_encoding.py",
    "Lib/lib2to3/tests/data/py2_test_grammar.py",
    "Lib/test/bad_coding2.py",
    "Lib/test/badsyntax_3131.py",
    "Lib/test/badsyntax_pep3120.py",
    "Lib/test/encoded_modules/module_iso_8859_1.py",
    "Lib/test/encoded_modules/module_koi8_r.py",
    "Lib/test/test_fstring.py",
    "Lib/test/test_grammar.py",
    "Lib/test/test_importlib/test_util.py",
    "Lib/test/test_named_expressions.py",
    "Lib/test/test_patma.py",
    "Lib/test/test_source_encoding.py",
    "Tools/c-analyzer/c_parser/parser/_delim.py",
    "Tools/i18n/pygettext.py",
    "Tools/test2to3/maintest.py",
    "Tools/test2to3/setup.py",
    "Tools/test2to3/test/test_foo.py",
    "Tools/test2to3/test2to3/hello.py",
]

Next, to benchmark the release build:

cargo build --release

hyperfine --ignore-failure --warmup 10 --runs 100 \
  "./target/release/ruff ./resources/test/cpython/ --no-cache" \
  "./target/release/ruff ./resources/test/cpython/"

Benchmark 1: ./target/release/ruff ./resources/test/cpython/ --no-cache
  Time (mean ± σ):     297.4 ms ±   4.9 ms    [User: 2460.0 ms, System: 67.2 ms]
  Range (min … max):   287.7 ms … 312.1 ms    100 runs

  Warning: Ignoring non-zero exit code.

Benchmark 2: ./target/release/ruff ./resources/test/cpython/
  Time (mean ± σ):      79.6 ms ±   7.3 ms    [User: 59.7 ms, System: 356.1 ms]
  Range (min … max):    62.4 ms … 111.2 ms    100 runs

  Warning: Ignoring non-zero exit code.

To benchmark against the ecosystem's existing tools:

hyperfine --ignore-failure --warmup 5 \
  "./target/release/ruff ./resources/test/cpython/ --no-cache" \
  "pylint --recursive=y resources/test/cpython/" \
  "pyflakes resources/test/cpython" \
  "autoflake --recursive --expand-star-imports --remove-all-unused-imports --remove-unused-variables --remove-duplicate-keys resources/test/cpython" \
  "pycodestyle resources/test/cpython" \
  "flake8 resources/test/cpython" \
  "python -m scripts.run_flake8 resources/test/cpython"

In order, these evaluate:

• Ruff
• Pylint
• Pyflakes
• autoflake
• pycodestyle
• Flake8
• Flake8, with a hack to enable multiprocessing on macOS

(You can poetry install from ./scripts to create a working environment for the above.)

Benchmark 1: ./target/release/ruff ./resources/test/cpython/ --no-cache
  Time (mean ± σ):     297.9 ms ±   7.0 ms    [User: 2436.6 ms, System: 65.9 ms]
  Range (min … max):   289.9 ms … 314.6 ms    10 runs

  Warning: Ignoring non-zero exit code.

Benchmark 2: pylint --recursive=y resources/test/cpython/
  Time (mean ± σ):     37.634 s ±  0.225 s    [User: 36.728 s, System: 0.853 s]
  Range (min … max):   37.201 s … 38.106 s    10 runs

  Warning: Ignoring non-zero exit code.

Benchmark 3: pyflakes resources/test/cpython
  Time (mean ± σ):     40.950 s ±  0.449 s    [User: 40.688 s, System: 0.229 s]
  Range (min … max):   40.348 s … 41.671 s    10 runs

  Warning: Ignoring non-zero exit code.

Benchmark 4: autoflake --recursive --expand-star-imports --remove-all-unused-imports --remove-unused-variables --remove-duplicate-keys resources/test/cpython
  Time (mean ± σ):     11.562 s ±  0.160 s    [User: 107.022 s, System: 1.143 s]
  Range (min … max):   11.417 s … 11.917 s    10 runs

Benchmark 5: pycodestyle resources/test/cpython
  Time (mean ± σ):     67.428 s ±  0.985 s    [User: 67.199 s, System: 0.203 s]
  Range (min … max):   65.313 s … 68.496 s    10 runs

  Warning: Ignoring non-zero exit code.

Benchmark 6: flake8 resources/test/cpython
  Time (mean ± σ):     116.099 s ±  1.178 s    [User: 115.217 s, System: 0.845 s]
  Range (min … max):   114.180 s … 117.724 s    10 runs

  Warning: Ignoring non-zero exit code.

Benchmark 7: python -m scripts.run_flake8 resources/test/cpython
  Time (mean ± σ):     20.477 s ±  0.349 s    [User: 142.372 s, System: 1.504 s]
  Range (min … max):   20.107 s … 21.183 s    10 runs

Summary
  './target/release/ruff ./resources/test/cpython/ --no-cache' ran
   38.81 ± 1.05 times faster than 'autoflake --recursive --expand-star-imports --remove-all-unused-imports --remove-unused-variables --remove-duplicate-keys resources/test/cpython'
   68.74 ± 1.99 times faster than 'python -m scripts.run_flake8 resources/test/cpython'
  126.33 ± 3.05 times faster than 'pylint --recursive=y resources/test/cpython/'
  137.46 ± 3.55 times faster than 'pyflakes resources/test/cpython'
  226.35 ± 6.23 times faster than 'pycodestyle resources/test/cpython'
  389.73 ± 9.92 times faster than 'flake8 resources/test/cpython'

License

MIT

Contributing

Contributions are welcome and hugely appreciated. To get started, check out the contributing guidelines.