modern-python

# Modern Python Guide for modern Python tooling and best practices, based on [trailofbits/cookiecutter-python](https://github.com/trailofbits/cookiecutter-python). ## When to Use This Skill - Creating a new Python project or package - Setting up `pyproject.toml` configuration - Configuring development tools (linting, formatting, testing) - Writing Python scripts with external dependencies - Migrating from legacy tools (when user requests it) ## When NOT to Use This Skill - **User wants to keep legacy tooling**: Respect existing workflows if explicitly requested - **Python < 3.11 required**: These tools target modern Python - **Non-Python projects**: Mixed codebases where Python isn't primary ## Anti-Patterns to Avoid | Avoid | Use Instead | |-------|-------------| | `[tool.ty]` python-version | `[tool.ty.environment]` python-version | | `uv pip install` | `uv add` and `uv sync` | | Editing pyproject.toml manually to add deps | `uv add <pkg>` / `uv remove <pkg>` | | `hatchling` build backend | `uv_build` (simpler, sufficient for most cases) | | Poetry | uv (faster, simpler, better ecosystem integration) | | requirements.txt | PEP 723 for scripts, pyproject.toml for projects | | mypy / pyright | ty (faster, from Astral team) | | `[project.optional-dependencies]` for dev tools | `[dependency-groups]` (PEP 735) | | Manual virtualenv activation (`source .venv/bin/activate`) | `uv run <cmd>` | | pre-commit | prek (faster, no Python runtime needed) | **Key principles:** - Al...