Ruff Formatter

Fast Python code formatter, drop-in replacement for Black with >99.9% compatibility.

Quick Reference

Format all files in current directory

ruff format .

Format specific file(s)

ruff format path/to/file.py

Check without modifying (CI/pre-commit)

ruff format --check .

Show diff of what would change

ruff format --diff .

Fixing Formatting Issues

When ruff format --check fails:

• Run ruff format . to auto-fix all formatting

• Review changes with git diff

• Commit the formatted code

For import sorting issues, run linter first:

ruff check --select I --fix . # Sort imports ruff format . # Then format

Format Suppression

Disable formatting for specific code:

fmt: off

matrix = [ [1, 0, 0], [0, 1, 0], [0, 0, 1], ]

fmt: on

x = 1 # fmt: skip

Configuration

In pyproject.toml or ruff.toml :

[tool.ruff.format] quote-style = "double" # or "single" indent-style = "space" # or "tab" line-length = 88 # default docstring-code-format = true

Exit Codes

• 0: Success (files formatted or already formatted)

• 1: With --check : files need formatting

• 2: Error (invalid config, CLI error)