python-pro

A guide for building modern Python 3.11+ applications with clear type annotations, asynchronous code, error handling, and automated tests. It uses tools such as mypy to check types, pytest to run tests, and Ruff and Black to check code quality and formatting.

In plain words
What is it for?
Use it to build Python packages and applications, write async code, define typed interfaces, create pytest test suites, improve performance, and check code with mypy, Ruff, and Black.
Why use it?
It reduces mistakes caused by unclear data types, untested behavior, and inconsistent code style. It also provides a repeatable way to check changes before they are finished.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/jeffallan/claude-skills/python-pro
Any agent
npx skills add Jeffallan/claude-skills --skill python-pro
Clone the repo
git clone --depth 1 https://github.com/Jeffallan/claude-skills

Made for: Claude Code, Codex.

Per session 83 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,424 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00083 $0.01424
Opus 5 $0.00042 $0.00712
Sonnet 5 $0.00017 $0.00285
Haiku 4.5 $0.00008 $0.00142

Measured 2d ago against content hash 83acbb761bc3, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

python-pro scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

skills/python-pro/SKILL.md · 180 lines

How it starts

The opening of the file, as written. The whole thing — 180 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Python Pro

Modern Python 3.11+ specialist focused on type-safe, async-first, production-ready code.

When to Use This Skill

  • Writing type-safe Python with complete type coverage
  • Implementing async/await patterns for I/O operations
  • Setting up pytest test suites with fixtures and mocking
  • Creating Pythonic code with comprehensions, generators, context managers
  • Building packages with Poetry and proper project structure
  • Performance optimization and profiling

Core Workflow

  1. Analyze codebase — Review structure, dependencies, type coverage, test suite
  2. Design interfaces — Define protocols, dataclasses, type aliases
  3. Implement — Write Pythonic code with full type hints and error handling
  4. Test — Create comprehensive pytest suite with >90% coverage
  5. Validate — Run mypy --strict, black, ruff
    • If mypy fails: fix type errors reported and re-run before proceeding
    • If tests fail: debug assertions, update fixtures, and iterate until green
    • If ruff/black reports issues: apply auto-fixes, then re-validate

Reference Guide

Load detailed guidance based on context:

Topic Reference Load When
Type System references/type-system.md Type hints, mypy, generics, Protocol
Async Patterns references/async-patterns.md async/await, asyncio, task groups
Standard Library references/standard-library.md pathlib, dataclasses, functools, itertools
Testing references/testing.md pytest, fixtures, mocking, parametrize
Packaging references/packaging.md poetry, pip, pyproject.toml, distribution

Constraints

MUST DO

  • Type hints for all function signatures and class attributes
  • PEP 8 compliance with black formatting
  • Comprehensive docstrings (Google style)
  • Test coverage exceeding 90% with pytest
  • Use X | None instead of Optional[X] (Python 3.10+)
  • Async/await for I/O-bound operations
  • Dataclasses over manual init methods
  • Context managers for resource handling

Read the full file on GitHub · 180 lines

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 180 lines · 83 tokens per session scan A 83acbb761bc3

Subscribe to this mod's changes

python-pro is a skill published in the GitHub repository Jeffallan/claude-skills (11,280 stars, last pushed 25d ago), licensed MIT. It adds 83 tokens to every session and 1,424 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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