ruff 0.0.25

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
• 📦 ESLint-inspired cache semantics
• 👀 TypeScript-inspired --watch semantics

ruff is a proof-of-concept and not yet intended for production use. It supports only a small subset of the Flake8 rules, and may crash on your codebase.

Read the launch blog post.

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 (requires Cargo on system):

repos:
- repo: https://github.com/charliermarsh/ruff
  rev: v0.0.25
  hooks:
    - id: lint

Configuration

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 F403

See ruff --help for more:

ruff
An extremely fast Python linter.

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

ARGS:
    <FILES>...

OPTIONS:
    -e, --exit-zero             Exit with status code "0", even upon detecting errors
    -h, --help                  Print help information
        --ignore <IGNORE>...    Comma-separated list of error codes to ignore
    -n, --no-cache              Disable cache reads
    -q, --quiet                 Disable all logging (but still exit with status code "1" upon
                                detecting errors)
        --select <SELECT>...    Comma-separated list of error codes to enable
    -v, --verbose               Enable verbose logging
    -w, --watch                 Run in watch mode by re-running whenever files change

Rules

Code	Name	Message
E501	LineTooLong	Line too long
F401	UnusedImport	... imported but unused
F403	ImportStarUsage	Unable to detect undefined names
F541	FStringMissingPlaceholders	f-string without any placeholders
F634	IfTuple	If test is a tuple, which is always True
F704	YieldOutsideFunction	a yield or yield from statement outside of a function/method
F706	ReturnOutsideFunction	a return statement outside of a function/method
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
R0205	UselessObjectInheritance	Class ... inherits from object

Development

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

Deployment

ruff is distributed on PyPI, and published via maturin.

See: .github/workflows/release.yaml.

Benchmarking

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.linter]
line-length = 88
exclude = [
    "Lib/ctypes/test/test_numbers.py",
    "Lib/dataclasses.py",
    "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/sqlite3/test/factory.py",
    "Lib/sqlite3/test/hooks.py",
    "Lib/sqlite3/test/regression.py",
    "Lib/sqlite3/test/transactions.py",
    "Lib/sqlite3/test/types.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/sortperf.py",
    "Lib/test/test_email/torture_test.py",
    "Lib/test/test_fstring.py",
    "Lib/test/test_genericpath.py",
    "Lib/test/test_getopt.py",
    "Lib/test/test_grammar.py",
    "Lib/test/test_htmlparser.py",
    "Lib/test/test_importlib/stubs.py",
    "Lib/test/test_importlib/test_files.py",
    "Lib/test/test_importlib/test_metadata_api.py",
    "Lib/test/test_importlib/test_open.py",
    "Lib/test/test_importlib/test_util.py",
    "Lib/test/test_named_expressions.py",
    "Lib/test/test_patma.py",
    "Lib/test/test_peg_generator/__main__.py",
    "Lib/test/test_pipes.py",
    "Lib/test/test_source_encoding.py",
    "Lib/test/test_weakref.py",
    "Lib/test/test_webbrowser.py",
    "Lib/tkinter/__main__.py",
    "Lib/tkinter/test/test_tkinter/test_variables.py",
    "Modules/_decimal/libmpdec/literature/fnt.py",
    "Modules/_decimal/tests/deccheck.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 1 \
  "./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):     353.6 ms ±   7.6 ms    [User: 2868.8 ms, System: 171.5 ms]
  Range (min … max):   344.4 ms … 367.3 ms    10 runs

Benchmark 2: ./target/release/ruff ./resources/test/cpython/
  Time (mean ± σ):      59.6 ms ±   2.5 ms    [User: 36.4 ms, System: 345.6 ms]
  Range (min … max):    55.9 ms …  67.0 ms    48 runs

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" \
  "pycodestyle --select E501 resources/test/cpython" \
  "flake8 resources/test/cpython" \
  "flake8 --select=F831,F541,F634,F403,F706,F901,E501 resources/test/cpython" \
  "python -m scripts.run_flake8 resources/test/cpython" \
  "python -m scripts.run_flake8 resources/test/cpython --select=F831,F541,F634,F403,F706,F901,E501"

In order, these evaluate:

• ruff
• Pylint
• PyFlakes
• autoflake
• pycodestyle
• pycodestyle, limited to the checks supported by ruff
• Flake8
• Flake8, limited to the checks supported by ruff
• Flake8, with a hack to enable multiprocessing on macOS
• Flake8, with a hack to enable multiprocessing on macOS, limited to the checks supported by ruff

(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):     469.3 ms ±  16.3 ms    [User: 2663.0 ms, System: 972.5 ms]
  Range (min … max):   445.2 ms … 494.8 ms    10 runs

Benchmark 2: pylint --recursive=y resources/test/cpython/
  Time (mean ± σ):     27.211 s ±  0.097 s    [User: 26.405 s, System: 0.799 s]
  Range (min … max):   27.056 s … 27.349 s    10 runs

Benchmark 3: pyflakes resources/test/cpython
  Time (mean ± σ):     27.309 s ±  0.033 s    [User: 27.137 s, System: 0.169 s]
  Range (min … max):   27.267 s … 27.372 s    10 runs

Benchmark 4: autoflake --recursive --expand-star-imports --remove-all-unused-imports --remove-unused-variables --remove-duplicate-keys resources/test/cpython
  Time (mean ± σ):      8.027 s ±  0.024 s    [User: 74.255 s, System: 0.953 s]
  Range (min … max):    7.969 s …  8.052 s    10 runs

Benchmark 5: pycodestyle resources/test/cpython
  Time (mean ± σ):     41.666 s ±  0.266 s    [User: 41.531 s, System: 0.132 s]
  Range (min … max):   41.295 s … 41.980 s    10 runs

Benchmark 6: pycodestyle --select E501 resources/test/cpython
  Time (mean ± σ):     14.547 s ±  0.077 s    [User: 14.466 s, System: 0.079 s]
  Range (min … max):   14.429 s … 14.695 s    10 runs

Benchmark 7: flake8 resources/test/cpython
  Time (mean ± σ):     75.700 s ±  0.152 s    [User: 75.254 s, System: 0.440 s]
  Range (min … max):   75.513 s … 76.014 s    10 runs

Benchmark 8: flake8 --select=F831,F541,F634,F403,F706,F901,E501 resources/test/cpython
  Time (mean ± σ):     75.122 s ±  0.532 s    [User: 74.677 s, System: 0.440 s]
  Range (min … max):   74.130 s … 75.606 s    10 runs

Benchmark 9: python -m scripts.run_flake8 resources/test/cpython
  Time (mean ± σ):     12.794 s ±  0.147 s    [User: 90.792 s, System: 0.738 s]
  Range (min … max):   12.606 s … 13.030 s    10 runs

Benchmark 10: python -m scripts.run_flake8 resources/test/cpython --select=F831,F541,F634,F403,F706,F901,E501
  Time (mean ± σ):     12.487 s ±  0.118 s    [User: 90.052 s, System: 0.714 s]
  Range (min … max):   12.265 s … 12.665 s    10 runs

Summary
  './target/release/ruff ./resources/test/cpython/ --no-cache' ran
   17.10 ± 0.60 times faster than 'autoflake --recursive --expand-star-imports --remove-all-unused-imports --remove-unused-variables --remove-duplicate-keys resources/test/cpython'
   26.60 ± 0.96 times faster than 'python -m scripts.run_flake8 resources/test/cpython --select=F831,F541,F634,F403,F706,F901,E501'
   27.26 ± 1.00 times faster than 'python -m scripts.run_flake8 resources/test/cpython'
   30.99 ± 1.09 times faster than 'pycodestyle --select E501 resources/test/cpython'
   57.98 ± 2.03 times faster than 'pylint --recursive=y resources/test/cpython/'
   58.19 ± 2.02 times faster than 'pyflakes resources/test/cpython'
   88.77 ± 3.14 times faster than 'pycodestyle resources/test/cpython'
  160.06 ± 5.68 times faster than 'flake8 --select=F831,F541,F634,F403,F706,F901,E501 resources/test/cpython'
  161.29 ± 5.61 times faster than 'flake8 resources/test/cpython'

License

MIT