# Modern Python

Configures Python projects with modern tooling (uv, ruff, ty).

- Repository: https://github.com/trailofbits/skills (7935 stars)
- Category: Writing
- License: CC-BY-SA-4.0
- Last updated: 2026-10-28
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add trailofbits/skills --skill modern-python -g -a claude-code -y`
Codex: `npx skills add trailofbits/skills --skill modern-python -g -a codex -y`
Cursor: `npx skills add trailofbits/skills --skill modern-python -g -a cursor -y`
Gemini CLI: `npx skills add trailofbits/skills --skill modern-python -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add trailofbits/skills`

## Description

Configures Python projects with modern tooling (uv, ruff, ty). Use when creating projects, writing standalone scripts, or migrating from pip/Poetry/mypy/black.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# 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:**
- Always use `uv add` and `uv remove` to manage dependencies
- Never manually activate or manage virtual environments, use `uv run` for all commands
- Use `[dependency-groups]` for dev/test/docs dependencies, not `[project.optional-dependencies]`

## Decision Tree

The rest: https://github.com/trailofbits/skills/blob/HEAD/plugins/modern-python/skills/modern-python/SKILL.md