Python Code Quality

Quick reference for Python code quality tools: ruff (linting & formatting), ty (type checking).

When to Use This Skill

Use this skill when... Use a focused sibling instead when...

Setting up a complete quality stack (lint + format + type-check) for a new project Tuning only ruff lint rule selection — use ruff-linting

Wiring ruff and ty into pre-commit and CI together Configuring only ruff formatter quirks — use ruff-formatting

Comparing ruff/ty/basedpyright at a high level before choosing tools Configuring strict basedpyright/ty type-checker rules — use basedpyright-type-checking or ty-type-checking

When This Skill Applies

Linting Python code
Code formatting
Type checking
Pre-commit hooks
CI/CD quality gates
Code style enforcement

Quick Reference

Ruff (Linter & Formatter)

Lint code

uv run ruff check .

Auto-fix issues

uv run ruff check --fix .

Format code

uv run ruff format .

Check and format

uv run ruff check --fix . && uv run ruff format .

Show specific rule

uv run ruff check --select E501 # Line too long

Ignore specific rule

uv run ruff check --ignore E501

ty (Type Checking)

Type check project

uv run ty check

Type check specific file

uv run ty check src/module.py

Check with explicit Python version

uv run ty check --python 3.11

Verbose output

uv run ty check --verbose

pyproject.toml Configuration

[tool.ruff] line-length = 88 target-version = "py311"

[tool.ruff.lint] select = [ "E", # pycodestyle errors "W", # pycodestyle warnings "F", # pyflakes "I", # isort "N", # pep8-naming "UP", # pyupgrade "B", # flake8-bugbear ] ignore = [ "E501", # line too long (handled by formatter) ]

[tool.ruff.lint.isort] known-first-party = ["myproject"]

[tool.ty] python-version = "3.11" exclude = [ "/pycache", "/.venv", "tests", ]

[tool.ty.rules] possibly-unbound = "warn"

Type Hints

Modern type hints (Python 3.10+)

def process_data( items: list[str], # Not List[str] config: dict[str, int], # Not Dict[str, int] optional: str | None = None, # Not Optional[str] ) -> tuple[bool, str]: # Not Tuple[bool, str] return True, "success"

Type aliases

from typing import TypeAlias

UserId: TypeAlias = int UserDict: TypeAlias = dict[str, str | int]

def get_user(user_id: UserId) -> UserDict: return {"id": user_id, "name": "Alice"}

Pre-commit Configuration

.pre-commit-config.yaml

repos:

repo: https://github.com/astral-sh/ruff-pre-commit rev: v0.1.9 hooks:
- id: ruff args: [--fix]
- id: ruff-format
repo: https://github.com/astral-sh/ty rev: v0.0.10 hooks:
- id: ty

Common Ruff Rules

E501: Line too long
F401: Unused import
F841: Unused variable
I001: Import not sorted
N806: Variable should be lowercase
B008: Function call in argument defaults

python-code-quality

Safety Notice

Copy this and send it to your AI assistant to learn