python-dev_skill

Overview

This skill provides an opinionated, production-ready Python development setup centered on uv, ty, ruff, pytest, and just. It automates a single-source-of-truth configuration with pyproject.toml and supplies templates for linting, type checking, testing, and project commands. Use it to bootstrap new projects or modernize existing repositories with a consistent developer workflow.

How this skill works

The skill scaffolds a src-layout project, pins a Python version with uv, and installs dev tooling into dependency groups in pyproject.toml. It includes ready-made pyproject.toml, Justfile, and pre-commit configurations that wire ruff for linting/formatting, ty for type checking, pytest for tests, and just for repeatable commands. Running just check executes type checks, linting, and formatting; other targets run tests, coverage, fixes, and dependency operations via uv.

When to use it

• Starting a new Python project and wanting a zero-decision stack
• Migrating older projects from pip/poetry/mypy/black/flake8 to a modern toolchain
• Setting up pyproject.toml as the canonical configuration file
• Adding consistent linting, formatting, and type checking across a team
• Creating a Justfile to standardize project commands and CI steps

Best practices

• Adopt the src layout always to avoid import pitfalls and improve packaging
• Keep all dev tools in a dev dependency-group inside pyproject.toml for reproducibility
• Pin the project Python version with uv to ensure consistent interpreter behavior
• Run just check frequently in pre-commit or CI to enforce types and linting
• Use ruff --fix and ruff format for automated formatting before committing

Example use cases

• Bootstrap a new library with uv init, pin Python, add dev deps, and run just check
• Modernize a legacy repo: uv add -r requirements.txt, replace mypy with ty, and swap black/flake8/isort with ruff
• Create a CI job that runs uv sync, just check, and pytest --cov to validate pull requests
• Add pre-commit hooks so ruff and basic repo checks run automatically on commit
• Provide contributors a single command set (just test, just fix, just install) for day-to-day work