lang-pythonlisted

# Skill: Language — Python > **Load trigger:** `"load lang-python skill"` > **Stack:** Python 3.11+, ruff, mypy, pytest, pytest-cov, uv or pip > **Token cost:** Low ## Toolchain Reference | Gate | Tool | Command | Config file | | --------- | ---------- | -------------------------------------------- | ------------------------------------------ | | Lint | ruff | `ruff check .` | `pyproject.toml [tool.ruff]` | | Format | ruff | `ruff format .` | `pyproject.toml [tool.ruff.format]` | | Typecheck | mypy | `mypy src/` | `pyproject.toml [tool.mypy]` | | Test | pytest | `pytest` | `pyproject.toml [tool.pytest.ini_options]` | | Coverage | pytest-cov | `pytest --cov=src --cov-report=term-missing` | `.coveragerc` | | Preflight | shell | `./scripts/preflight.sh` | `scripts/preflight.sh` | ## File Layout Convention ``` src/ [package_name]/ __init__.py services/ ← business logic utils/ ← pure functions models/ ← data models (Pydantic or dataclasses) api/ ← HTTP handlers / FastAPI routers tests/ test_services/ ← mirrors src/services/ test_utils/ ← m