trailofbits-skills/plugins/modern-python

Modern Python

Modern Python tooling and best practices using uv, ruff, ty, and pytest. Based on patterns from trailofbits/cookiecutter-python.

Author: William Tan

When to Use

• Setting up a new Python project with modern, fast tooling
• Replacing pip/virtualenv with uv for faster dependency management
• Replacing flake8/black/isort with ruff for unified linting and formatting
• Replacing mypy with ty for faster type checking
• Adding pre-commit hooks and security scanning to an existing project

What It Covers

Core Tools:

• uv - Package/dependency management (replaces pip, virtualenv, pip-tools, pipx, pyenv)
• ruff - Linting and formatting (replaces flake8, black, isort, pyupgrade)
• ty - Type checking (replaces mypy, pyright)
• pytest - Testing with coverage enforcement
• prek - Pre-commit hooks (replaces pre-commit)

Security Tools:

• shellcheck - Shell script linting
• detect-secrets - Secret detection in commits
• actionlint - GitHub Actions syntax validation
• zizmor - GitHub Actions security audit
• pip-audit - Dependency vulnerability scanning
• Dependabot - Automated dependency updates with supply chain protection

Standards:

• pyproject.toml - Single configuration file with dependency groups (PEP 735)
• PEP 723 - Inline script metadata for single-file scripts
• src/ layout - Standard package structure
• Python 3.11+ - Minimum version requirement

Hook: Legacy Command Interception

This plugin includes a SessionStart hook that prepends PATH shims for python, pip, pipx, and uv. When Claude runs a bare python, pip, or pipx command, the shell resolves to the shim, which prints an error with the correct uv alternative and exits non-zero. The suggested alternative always uses the exact command name python (never python3) so it also works outside a project; see the header comment in hooks/shims/python for the full rationale.

The shims sit on PATH, so they see every subprocess a tool spawns, not only what Claude types. That is why the intercepted set is narrow: it covers the invocations uv run and uv add genuinely replace, and passes the rest through to the real binary. python -c, python -m <module> and python - read a program from the command line, an installed module, or stdin, so none of them resolves a script against a project's dependencies; uv pip carrying --project, --directory or --target is a tool building an environment it owns. Redirecting those broke real tooling, including prek hook installation and any script piping into python3 - (#207).

Intercepted Command	Suggested Alternative
python ...	uv run python ...
python -m pip	uv add/uv remove
pip install pkg	uv add pkg or uv run --with pkg
pip uninstall pkg	uv remove pkg
pip freeze	uv export
uv pip ...	uv add/uv remove/uv sync
(passed through)	python -c, python -m <module>, python -, and uv pip with --project, --directory or --target
pipx install <pkg>	uv tool install <pkg>
pipx run <pkg>	uvx <pkg>
pipx uninstall <pkg>	uv tool uninstall <pkg>
pipx upgrade <pkg>	uv tool upgrade <pkg>
pipx upgrade-all	uv tool upgrade --all
pipx ensurepath	uv tool update-shell
pipx inject <pkg> <dep>	uv tool install --with <dep> <pkg>
pipx list	uv tool list

Commands like grep python, which python, and cat python.txt work normally because python is a shell argument, not the command being invoked.

Installation

/plugin install trailofbits/skills/plugins/modern-python