ruff 0.0.251

An extremely fast Python linter, written in Rust.

Ruff

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An extremely fast Python linter, written in Rust.

Linting the CPython codebase from scratch.

• ⚡️ 10-100x faster than existing linters
• 🐍 Installable via pip
• 🛠️ pyproject.toml support
• 🤝 Python 3.11 compatibility
• 📦 Built-in caching, to avoid re-analyzing unchanged files
• 🔧 Autofix support, for automatic error correction (e.g., automatically remove unused imports)
• 📏 Over 400 built-in rules (and growing)
• ⚖️ Near-parity with the built-in Flake8 rule set
• 🔌 Native re-implementations of dozens of Flake8 plugins, like flake8-bugbear
• ⌨️ First-party editor integrations for VS Code and more
• 🌎 Monorepo-friendly, with hierarchical and cascading configuration

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 dozens of plugins), isort, pydocstyle, yesqa, eradicate, pyupgrade, and autoflake, all while executing tens or hundreds of times faster than any individual tool.

Ruff is extremely actively developed and used in major open-source projects like:

• pandas
• FastAPI
• Transformers (Hugging Face)
• Apache Airflow
• SciPy

...and many more.

Read the launch blog post or the most recent project update.

Testimonials

Sebastián Ramírez, creator of FastAPI:

Ruff is so fast that sometimes I add an intentional bug in the code just to confirm it's actually running and checking the code.

Nick Schrock, founder of Elementl, co-creator of GraphQL:

Why is Ruff a gamechanger? Primarily because it is nearly 1000x faster. Literally. Not a typo. On our largest module (dagster itself, 250k LOC) pylint takes about 2.5 minutes, parallelized across 4 cores on my M1. Running ruff against our entire codebase takes .4 seconds.

Bryan Van de Ven, co-creator of Bokeh, original author of Conda:

Ruff is ~150-200x faster than flake8 on my machine, scanning the whole repo takes ~0.2s instead of ~20s. This is an enormous quality of life improvement for local dev. It's fast enough that I added it as an actual commit hook, which is terrific.

Timothy Crosley, creator of isort:

Just switched my first project to Ruff. Only one downside so far: it's so fast I couldn't believe it was working till I intentionally introduced some errors.

Tim Abbott, lead developer of Zulip:

This is just ridiculously fast... ruff is amazing.

Table of Contents

For more, see the documentation.

1. Installation and Usage
2. Configuration
3. Supported Rules
4. Contributing
5. Support
6. Acknowledgements
7. Who's Using Ruff?
8. License

Installation and Usage

For more, see the documentation.

Installation

Ruff is available as ruff on PyPI:

pip install ruff

For macOS Homebrew and Linuxbrew users, Ruff is also available as ruff on Homebrew:

brew install ruff

For Conda users, Ruff is also available as ruff on conda-forge:

conda install -c conda-forge ruff

For Arch Linux users, Ruff is also available as ruff on the official repositories:

pacman -S ruff

For Alpine users, Ruff is also available as ruff on the testing repositories:

apk add ruff

Usage

To run Ruff, try any of the following:

ruff check .                        # Lint all files in the current directory (and any subdirectories)
ruff check path/to/code/            # Lint all files in `/path/to/code` (and any subdirectories)
ruff check path/to/code/*.py        # Lint all `.py` files in `/path/to/code`
ruff check path/to/code/to/file.py  # Lint `file.py`

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

ruff check path/to/code/ --watch

Ruff also works with pre-commit:

- repo: https://github.com/charliermarsh/ruff-pre-commit
  # Ruff version.
  rev: 'v0.0.251'
  hooks:
    - id: ruff

Or, to enable autofix:

- repo: https://github.com/charliermarsh/ruff-pre-commit
  # Ruff version.
  rev: 'v0.0.251'
  hooks:
    - id: ruff
      args: [--fix, --exit-non-zero-on-fix]

Configuration

Ruff can be configured via a pyproject.toml file, a ruff.toml file, or through the command line.

For a complete enumeration of the available configuration options, see the documentation.

Configure via pyproject.toml

If left unspecified, the default configuration is equivalent to:

[tool.ruff]
# Enable Pyflakes `E` and `F` codes by default.
select = ["E", "F"]
ignore = []

# Allow autofix for all enabled rules (when `--fix`) is provided.
fixable = ["A", "B", "C", "D", "E", "F", "..."]
unfixable = []

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

# Same as Black.
line-length = 88

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

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

[tool.ruff.mccabe]
# Unlike Flake8, default to a complexity level of 10.
max-complexity = 10

As an example, the following would configure Ruff to: (1) enforce flake8-bugbear rules, in addition to the defaults; (2) avoid enforcing line-length violations (E501); (3) avoid attempting to fix flake8-bugbear (B) violations; and (3) ignore import-at-top-of-file violations (E402) in __init__.py files:

[tool.ruff]
# Enable flake8-bugbear (`B`) rules.
select = ["E", "F", "B"]

# Never enforce `E501` (line length violations).
ignore = ["E501"]

# Avoid trying to fix flake8-bugbear (`B`) violations.
unfixable = ["B"]

# Ignore `E402` (import violations) in all `__init__.py` files, and in `path/to/file.py`.
[tool.ruff.per-file-ignores]
"__init__.py" = ["E402"]
"path/to/file.py" = ["E402"]

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"

Ruff mirrors Flake8's rule code system, in which each rule code consists of a one-to-three letter prefix, followed by three digits (e.g., F401). The prefix indicates that "source" of the rule (e.g., F for Pyflakes, E for pycodestyle, ANN for flake8-annotations). The set of enabled rules is determined by the select and ignore options, which support both the full code (e.g., F401) and the prefix (e.g., F).

As a special-case, Ruff also supports the ALL code, which enables all rules. Note that some of the pydocstyle rules conflict (e.g., D203 and D211) as they represent alternative docstring formats. Enabling ALL without further configuration may result in suboptimal behavior, especially for the pydocstyle plugin.

If you're wondering how to configure Ruff, here are some recommended guidelines:

• Prefer select and ignore over extend-select and extend-ignore, to make your rule set explicit.
• Use ALL with discretion. Enabling ALL will implicitly enable new rules whenever you upgrade.
• Start with a small set of rules (select = ["E", "F"]) and add a category at-a-time. For example, you might consider expanding to select = ["E", "F", "B"] to enable the popular flake8-bugbear extension.
• By default, Ruff's autofix is aggressive. If you find that it's too aggressive for your liking, consider turning off autofix for specific rules or categories (see: FAQ).

Configure via ruff.toml

As an alternative to pyproject.toml, Ruff will also respect a ruff.toml file, which implements an equivalent schema (though the [tool.ruff] hierarchy can be omitted). For example, the pyproject.toml described above would be represented via the following ruff.toml:

# Enable flake8-bugbear (`B`) rules.
select = ["E", "F", "B"]

# Never enforce `E501` (line length violations).
ignore = ["E501"]

# Avoid trying to fix flake8-bugbear (`B`) violations.
unfixable = ["B"]

# Ignore `E402` (import violations) in all `__init__.py` files, and in `path/to/file.py`.
[per-file-ignores]
"__init__.py" = ["E402"]
"path/to/file.py" = ["E402"]

For a full list of configurable options, see the list of all options.

Command-line interface

Some configuration settings can be provided via the command-line, such as those related to rule enablement and disablement, file discovery, logging level, and more:

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

See ruff help for more on Ruff's top-level commands:

Ruff: An extremely fast Python linter.

Usage: ruff [OPTIONS] <COMMAND>

Commands:
  check   Run Ruff on the given files or directories (default)
  rule    Explain a rule
  config  List or describe the available configuration options
  linter  List all supported upstream linters
  clean   Clear any caches in the current directory and any subdirectories
  help    Print this message or the help of the given subcommand(s)

Options:
  -h, --help     Print help
  -V, --version  Print version

Log levels:
  -v, --verbose  Enable verbose logging
  -q, --quiet    Print lint violations, but nothing else
  -s, --silent   Disable all logging (but still exit with status code "1" upon detecting lint violations)

For help with a specific command, see: `ruff help <command>`.

Or ruff help check for more on the linting command:

Run Ruff on the given files or directories (default)

Usage: ruff check [OPTIONS] [FILES]...

Arguments:
  [FILES]...  List of files or directories to check

Options:
      --fix
          Attempt to automatically fix lint violations
      --show-source
          Show violations with source code
      --show-fixes
          Show an enumeration of all autofixed lint violations
      --diff
          Avoid writing any fixed files back; instead, output a diff for each changed file to stdout
  -w, --watch
          Run in watch mode by re-running whenever files change
      --fix-only
          Fix any fixable lint violations, but don't report on leftover violations. Implies `--fix`
      --format <FORMAT>
          Output serialization format for violations [env: RUFF_FORMAT=] [possible values: text, json, junit, grouped, github, gitlab, pylint]
      --target-version <TARGET_VERSION>
          The minimum Python version that should be supported
      --config <CONFIG>
          Path to the `pyproject.toml` or `ruff.toml` file to use for configuration
      --statistics
          Show counts for every rule with at least one violation
      --add-noqa
          Enable automatic additions of `noqa` directives to failing lines
      --show-files
          See the files Ruff will be run against with the current settings
      --show-settings
          See the settings Ruff will use to lint a given Python file
  -h, --help
          Print help

Rule selection:
      --select <RULE_CODE>
          Comma-separated list of rule codes to enable (or ALL, to enable all rules)
      --ignore <RULE_CODE>
          Comma-separated list of rule codes to disable
      --extend-select <RULE_CODE>
          Like --select, but adds additional rule codes on top of the selected ones
      --per-file-ignores <PER_FILE_IGNORES>
          List of mappings from file pattern to code to exclude
      --fixable <RULE_CODE>
          List of rule codes to treat as eligible for autofix. Only applicable when autofix itself is enabled (e.g., via `--fix`)
      --unfixable <RULE_CODE>
          List of rule codes to treat as ineligible for autofix. Only applicable when autofix itself is enabled (e.g., via `--fix`)

File selection:
      --exclude <FILE_PATTERN>         List of paths, used to omit files and/or directories from analysis
      --extend-exclude <FILE_PATTERN>  Like --exclude, but adds additional files and directories on top of those already excluded
      --respect-gitignore              Respect file exclusions via `.gitignore` and other standard ignore files
      --force-exclude                  Enforce exclusions, even for paths passed to Ruff directly on the command-line

Miscellaneous:
  -n, --no-cache
          Disable cache reads
      --isolated
          Ignore all configuration files
      --cache-dir <CACHE_DIR>
          Path to the cache directory [env: RUFF_CACHE_DIR=]
      --stdin-filename <STDIN_FILENAME>
          The name of the file when passing it through stdin
  -e, --exit-zero
          Exit with status code "0", even upon detecting lint violations
      --exit-non-zero-on-fix
          Exit with a non-zero status code if any files were modified via autofix, even if no lint violations remain

Log levels:
  -v, --verbose  Enable verbose logging
  -q, --quiet    Print lint violations, but nothing else
  -s, --silent   Disable all logging (but still exit with status code "1" upon detecting lint violations)

pyproject.toml discovery

Similar to ESLint, Ruff supports hierarchical configuration, such that the "closest" pyproject.toml file in the directory hierarchy is used for every individual file, with all paths in the pyproject.toml file (e.g., exclude globs, src paths) being resolved relative to the directory containing the pyproject.toml file.

There are a few exceptions to these rules:

1. In locating the "closest" pyproject.toml file for a given path, Ruff ignores any pyproject.toml files that lack a [tool.ruff] section.
2. If a configuration file is passed directly via --config, those settings are used for across files. Any relative paths in that configuration file (like exclude globs or src paths) are resolved relative to the current working directory.
3. If no pyproject.toml file is found in the filesystem hierarchy, Ruff will fall back to using a default configuration. If a user-specific configuration file exists at ${config_dir}/ruff/pyproject.toml, that file will be used instead of the default configuration, with ${config_dir} being determined via the dirs crate, and all relative paths being again resolved relative to the current working directory.
4. Any pyproject.toml-supported settings that are provided on the command-line (e.g., via --select) will override the settings in every resolved configuration file.

Unlike ESLint, Ruff does not merge settings across configuration files; instead, the "closest" configuration file is used, and any parent configuration files are ignored. In lieu of this implicit cascade, Ruff supports an extend field, which allows you to inherit the settings from another pyproject.toml file, like so:

# Extend the `pyproject.toml` file in the parent directory.
extend = "../pyproject.toml"
# But use a different line length.
line-length = 100

All of the above rules apply equivalently to ruff.toml files. If Ruff detects both a ruff.toml and pyproject.toml file, it will defer to the ruff.toml.

Python file discovery

When passed a path on the command-line, Ruff will automatically discover all Python files in that path, taking into account the exclude and extend-exclude settings in each directory's pyproject.toml file.

By default, Ruff will also skip any files that are omitted via .ignore, .gitignore, .git/info/exclude, and global gitignore files (see: respect-gitignore).

Files that are passed to ruff directly are always linted, regardless of the above criteria. For example, ruff check /path/to/excluded/file.py will always lint file.py.

Rule resolution

The set of enabled rules is controlled via the select and ignore settings, along with the extend-select and extend-ignore modifiers.

To resolve the enabled rule set, Ruff may need to reconcile select and ignore from a variety of sources, including the current pyproject.toml, any inherited pyproject.toml files, and the CLI (e.g., --select).

In those scenarios, Ruff uses the "highest-priority" select as the basis for the rule set, and then applies any extend-select, ignore, and extend-ignore adjustments. CLI options are given higher priority than pyproject.toml options, and the current pyproject.toml file is given higher priority than any inherited pyproject.toml files.

For example, given the following pyproject.toml file:

[tool.ruff]
select = ["E", "F"]
ignore = ["F401"]

Running ruff check --select F401 would result in Ruff enforcing F401, and no other rules.

Running ruff check --extend-select B would result in Ruff enforcing the E, F, and B rules, with the exception of F401.

Suppressing errors

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

To ignore a violation inline, Ruff uses a noqa system similar to Flake8. To ignore an individual violation, 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_ violations.
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 string, like so:

"""Lorem ipsum dolor sit amet.

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor.
"""  # noqa: E501

To ignore all violations across an entire file, add # ruff: noqa to any line in the file, like so:

# ruff: noqa

To ignore a specific rule across an entire file, add # ruff: noqa: {code} to any line in the file, like so:

# ruff: noqa: F841

Or see the per-file-ignores configuration setting, which enables the same functionality via a pyproject.toml file.

Note that Ruff will also respect Flake8's # flake8: noqa directive, and will treat it as equivalent to # ruff: noqa.

Automatic error suppression

Ruff supports several workflows to aid in noqa management.

First, Ruff provides a special rule code, RUF100, to enforce that your noqa directives are "valid", in that the violations they say they ignore are actually being triggered on that line (and thus suppressed). You can run ruff check /path/to/file.py --extend-select RUF100 to flag unused noqa directives.

Second, Ruff can automatically remove unused noqa directives via its autofix functionality. You can run ruff check /path/to/file.py --extend-select RUF100 --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 check /path/to/file.py --add-noqa to automatically add noqa directives to all failing lines, with the appropriate rule codes.

Action comments

Ruff respects isort's action comments (# isort: skip_file, # isort: on, # isort: off, # isort: skip, and # isort: split), which enable selectively enabling and disabling import sorting for blocks of code and other inline configuration.

See the isort documentation for more.

Exit codes

By default, Ruff exits with the following status codes:

• 0 if no violations were found, or if all present violations were fixed automatically.
• 1 if violations were found.
• 2 if Ruff terminates abnormally due to invalid configuration, invalid CLI options, or an internal error.

This convention mirrors that of tools like ESLint, Prettier, and RuboCop.

Ruff supports two command-line flags that alter its exit code behavior:

• --exit-zero will cause Ruff to exit with a status code of 0 even if violations were found. Note that Ruff will still exit with a status code of 2 if it terminates abnormally.
• --exit-non-zero-on-fix will cause Ruff to exit with a status code of 1 if violations were found, even if all such violations were fixed automatically. Note that the use of --exit-non-zero-on-fix can result in a non-zero exit code even if no violations remain after autofixing.

Autocompletion

Ruff supports autocompletion for most shells. A shell-specific completion script can be generated by ruff generate-shell-completion <SHELL>, where <SHELL> is one of bash, elvish, fig, fish, powershell, or zsh.

The exact steps required to enable autocompletion will vary by shell. For example instructions, see the Poetry or ripgrep documentation.

As an example: to enable autocompletion for Zsh, run ruff generate-shell-completion zsh > ~/.zfunc/_ruff. Then add the following line to your ~/.zshrc file, if they're not already present:

fpath+=~/.zfunc
autoload -Uz compinit && compinit

Supported Rules

Ruff supports over 400 lint rules, many of which are inspired by popular tools like Flake8, isort, pyupgrade, and others. Regardless of the rule's origin, Ruff re-implements every rule in Rust as a first-party feature.

By default, Ruff enables Flake8's E and F rules. Ruff supports all rules from the F category, and a subset of the E category, omitting those stylistic rules made obsolete by the use of an autoformatter, like Black.

For a complete enumeration, see the list of rules in the Ruff documentation.

Contributing

Contributions are welcome and highly appreciated. To get started, check out the contributing guidelines. You can also join us on Discord.

Support

Having trouble? Check out the existing issues on GitHub, or feel free to open a new one.

You can also ask for help on Discord.

Acknowledgements

Ruff's linter draws on both the APIs and implementation details of many other tools in the Python ecosystem, especially Flake8, Pyflakes, pycodestyle, pydocstyle, pyupgrade, and isort.

In some cases, Ruff includes a "direct" Rust port of the corresponding tool. We're grateful to the maintainers of these tools for their work, and for all the value they've provided to the Python community.

Ruff's autoformatter is built on a fork of Rome's rome_formatter, and again draws on both the APIs and implementation details of Rome, Prettier, and Black.

Ruff is also influenced by a number of tools outside the Python ecosystem, like Clippy and ESLint.

Ruff is the beneficiary of a large number of contributors.

Ruff is released under the MIT license.

Who's Using Ruff?

Ruff is used in a number of major open-source projects, including:

• pandas
• FastAPI
• Transformers (Hugging Face)
• Diffusers (Hugging Face)
• Apache Airflow
• SciPy
• Zulip
• Bokeh
• Pydantic
• Dagster
• Dagger
• Sphinx
• Hatch
• PDM
• Jupyter
• Great Expectations
• ONNX
• Polars
• Ibis
• Synapse (Matrix)
• SnowCLI (Snowflake)
• Dispatch (Netflix)
• Saleor
• Pynecone
• OpenBB
• Home Assistant
• Pylint
• Cryptography (PyCA)
• cibuildwheel (PyPA)
• build (PyPA)
• Babel
• featuretools
• meson-python
• ZenML

License

MIT