python-development_skill

Overview

This skill teaches modern Python development for Python 3.12+ with practical patterns for Django/FastAPI services, async code, and production-ready projects. It focuses on typing, project layout, testing, and tooling that improve reliability and developer productivity. Use it to build APIs, data pipelines, or automation with clear, maintainable code.

How this skill works

It inspects and applies idiomatic project structure, pyproject.toml configuration, and recommended linters/type checkers (ruff, mypy). It demonstrates typed code patterns, async primitives, FastAPI endpoints, and testing approaches using pytest and AsyncMock. It highlights production best practices like using pathlib, Pydantic/dataclasses, and async context management for resources.

When to use it

• Starting a new Python 3.12+ project (library, service, CLI).
• Building HTTP APIs with FastAPI or integrating async I/O.
• Implementing strict static typing and runtime validation with Pydantic.
• Setting up CI with linting, formatting, and type checks.
• Writing async tests and mocking async dependencies.

Best practices

• Use a src/ layout and declare requires-python >=3.12 in pyproject.toml.
• Enforce linting and formatting with ruff and set mypy strict mode for types.
• Prefer pathlib.Path for file paths and contextlib.asynccontextmanager for async resources.
• Model external data with Pydantic or dataclasses and keep validation close to boundaries.
• Use asyncio.gather for concurrent I/O tasks and stream large files with async iterators.

Example use cases

• Create a FastAPI user service with Pydantic request/response models and dependency-injected DB access.
• Implement an async data ingestion pipeline that fetches many URLs concurrently and streams large files to storage.
• Set up a library with strict type coverage using mypy and ruff, plus unit and async tests with pytest and AsyncMock.
• Build automation scripts that use pathlib and type hints for predictable, testable behavior.