Python Skill

Skill ID: python
Version: 2.0
Updated: 2026-07-16

Purpose

Activate this skill when A Python package, service, async task, CLI, or data-processing module changes.

Why

A typed module contract, dependency and environment specification, tests, packaging evidence, and operational error behavior is the minimum reviewable deliverable for this domain. A generic "inspect, change, test" loop omits the domain decisions and failure evidence needed for production use.

Trigger Conditions

A Python package, service, async task, CLI, or data-processing module changes.
The requester expects an implementation, design, audit, or release decision in this domain.

Required Inputs

The exact target and acceptance criteria.
Repository-pinned versions, environment constraints, and available evidence.
Data classification, effect permissions, and owner where the procedure can affect external systems.

Produced Artifacts

A typed module contract
dependency and environment specification
tests
packaging evidence
operational error behavior.

Procedure

Inspect pyproject, supported Python versions, dependency groups, formatter, type checker, and test conventions.
Model types and exceptions at public boundaries; validate external data and avoid mutable defaults.
For async or multiprocessing code, define cancellation, cleanup, serialization, and concurrency ownership.
Write pytest cases with isolated temp paths, clocks, environment, and network; add property tests for invariant-heavy logic.
Run the pinned formatter, linter, type checker, tests, build, and package metadata validation.

Verification

Verify wheels and source distributions build, imports work in a clean environment, type checks pass, and resources close on exceptions.

Unhappy Paths and Recovery

If dependency resolution diverges, reproduce from the lock or constraints file. If typing requires broad ignores, narrow the interface rather than masking errors.

Concrete Example

Create an async client with httpx timeouts, typed response models, retry classification, cancellation-safe cleanup, and respx tests.

Do Not Use This Skill When

Do not use for notebooks whose primary goal is exploratory analysis rather than maintained software.

Tradeoffs

The required domain artifacts and verification cost more than a generic implementation pass, but they expose assumptions, safety gates, and operational limits before release.

Anti-Patterns

Substituting a generic checklist for the domain procedure above.
Claiming a gate passed without retaining the exact command, inspected artifact, or observed signal.
Expanding scope or executing an external effect without target-specific approval.

Enterprise Considerations

Apply repository ownership, separation of duties, data residency and retention, audit evidence, and approved-tool policies to every produced artifact. Redact secrets and regulated data from examples and logs.

Checklist

Trigger and anti-trigger evaluated
Required inputs and domain artifacts complete
Procedure followed in order
Verification evidence retained
Recovery, rollback, owner, and residual risk recorded

Authoritative Sources

Changelog

2.0 (2026-07-16): Replaced the cloned generic procedure with domain-specific artifacts, workflow, recovery, examples, and sources.
1.1: Initial standardized structure.