python-router

name	python-router
description	Route Python work to the smallest useful skill. Use for Python coding, design, typing, errors and logging, decorators and other abstractions, iterators and generators, data shapes, concurrency, testing, verification, and quality-tool selection.
globs	["**/pyproject.toml","**/*.py","**/*.pyi"]

Python Router

Load this first for non-trivial Python work, then load only the smallest useful follow-on skill.

Working stance

• Start from the concrete problem: the failing call, the offending boundary, the hot loop, or the leaky exception.
• Prefer one language skill plus at most one domain or quality skill.
• Use the general leta skill for code navigation, references, and refactors; use grepai for semantic search.
• If the answer starts turning into a tutorial, stop and cut back to the decision that matters.
• When a local fix needs Any, broad except, runtime introspection, or a metaclass, re-check the design before keeping the patch.

Route by question

• Generics, TypeVar, ParamSpec, TypeIs, TypeGuard, NewType, overloads, typed kwargs, or public API typing: python-types-and-apis
• Exception hierarchy, raise … from …, narrow except, parameterized logging, or logger.exception discipline: python-errors-and-logging
• Decorators, descriptors, context managers, metaclasses, or multiple dispatch: python-abstractions
• Iterators, generators, lazy pipelines, or refactoring by extracting an iterator or context manager: python-iterators-and-generators
• msgspec.Struct, dataclasses, TypedDict, attrs, tagged unions, or typed kwargs payloads: python-data-shapes
• Threads, asyncio, multiprocessing, or PEP 734 subinterpreters: python-concurrency
• pytest at depth: fixtures, parametrization, marks, plugins, snapshots, async tests: python-testing
• Selecting between Hypothesis, CrossHair, and mutmut: python-verification; deep dives in hypothesis, crosshair, mutmut
• Dead-code detection, clone and complexity scans, or profiling: python-quality-tools

Pairing rules

• Web or worker boundaries usually pair python-errors-and-logging with python-concurrency or python-data-shapes.
• Library API work usually pairs python-types-and-apis with python-data-shapes (when the surface is data-shaped) or python-abstractions (when it is behaviour-shaped).
• Refactoring a deep for loop usually pairs python-iterators-and-generators with python-types-and-apis.
• Verification work loads python-verification first to choose the tool, then exactly one of hypothesis, crosshair, or mutmut.

Escalate when

• type errors are silenced with # type: ignore or Any without a comment explaining the invariant,
• a public API needs a metaclass, runtime getattr dispatch, or eval,
• async code grows shared mutable state and cancellation semantics at once,
• performance claims appear before measurements,
• except Exception: survives review without a documented reason.

Read routing-matrix.md only when the route is still unclear.