Try out rust-python-parser (nom-based)
An extremely fast Python linter, written in Rust.
pippyproject.toml support--fix support--watch supportRead the launch blog post.
Available as ruff on PyPI:
pip install ruff
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: v0.0.48 hooks: - id: lint
ruff is configurable both via pyproject.toml and the command line.
For example, you could configure ruff to only enforce a subset of rules with:
[tool.ruff] line-length = 88 select = [ "F401", "F403", ]
Alternatively, on 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: -v, --verbose Enable verbose logging -q, --quiet 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 -f, --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 -h, --help Print help information -V, --version Print version information
Exclusions are based on globs, and can be either:
.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 ).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).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 (experimental) 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.
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.
ruff's goal is to achieve feature parity with Flake8 when used (1) without plugins, (2) alongside Black, and (3) on Python 3 code.
Under those conditions, ruff implements 44 out of 60 rules. (ruff is missing: 14 rules related to string .format calls, 1 rule related to docstring parsing, and 1 rule related to redefined variables.)
ruff also implements some of the most popular Flake8 plugins natively, including:
Beyond rule-set parity, ruff suffers from the following limitations vis-à-vis Flake8:
The ✅ emoji indicates a rule is enabled by default.
The 🛠 emoji indicates that a rule is automatically fixable by the --fix command-line option.
| Code | Name | Message | ||
|---|---|---|---|---|
| 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: ... | ✅ | |
| 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/method | ✅ | |
| 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 | ✅ | |
| 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 | ||
| SPR001 | SuperCallWithParameters | Use super() instead of super(__class__, self) | 🛠 | |
| T201 | PrintFound | print found | 🛠 | |
| T203 | PPrintFound | pprint found | 🛠 | |
| U001 | UselessMetaclassType | __metaclass__ = type is implied | 🛠 | |
| R001 | UselessObjectInheritance | Class ... inherits from object | 🛠 | |
| R002 | NoAssertEquals | assertEquals is deprecated, use assertEqual instead | 🛠 | |
| M001 | UnusedNOQA | Unused noqa directive | 🛠 |
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:
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@v2 - name: Install Python uses: actions/setup-python@v2 with: python-version: "3.10" - name: Install dependencies run: | python -m pip install --upgrade pip pip install ruff - name: Run ruff run: ruff .
ruff is written in Rust (1.63.0). You'll need to install the Rust toolchain for development.
Assuming you have cargo installed, you can run:
cargo run resources/test/fixtures cargo fmt cargo clippy cargo test
ruff is distributed on PyPI, and published via maturin.
See: .github/workflows/release.yaml.
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:
(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'
MIT
Contributions are welcome and hugely appreciated. To get started, check out the contributing guidelines.