---
description: Python style per PEP 8 (+ PEP 257 docstrings)
globs: ["**/*.py"]
alwaysApply: true
---

- 4-space indent, no tabs. Lines ≤ 79 chars (72 for comments/docstrings).
- Two blank lines around top-level defs/classes; one between methods.
- `snake_case` functions/variables; `CapWords` classes; `UPPER_CASE` constants. Exceptions end in `Error`.
- `_leading_underscore` for non-public. First args `self` / `cls`. Never name things `l`, `O`, `I`.
- One import per line, grouped stdlib / third-party / local with blank lines; no wildcard imports.
- No spaces inside brackets or before `,;:`; single spaces around binary operators; break long lines before the operator.
- Docstrings (`"""..."""`) on public modules/classes/functions/methods; imperative mood, end with a period.
- Compare to `None` with `is`/`is not`; use `isinstance(...)`; prefer truthiness (`if not seq:`).
- No bare `except:`; use `def` over a named lambda.
- Type hints optional, static-only: `def f(x: int) -> str:`, `Optional[T]` / `T | None`.
- Let `ruff` / `black` enforce layout; value module-level consistency over rigid compliance.