Generate Pythonic Code with Modern Features

This skill provides expert-level guidance for modern Python development practices - type hints, PEP 8 style, idiomatic Pythonic code, and properly formatted docstrings in Google or NumPy style. Modern Python features covered: type hints for Python 3.10+ (function signatures with built-in generics like list[dict[str, Any]], and the | union-type syntax), structural pattern matching (match/case on list patterns including wildcard and rest captures), and data classes:

from dataclasses import dataclass, field
from datetime import datetime

@dataclass
class User:
    id: int
    name: str
    email: str
    created_at: datetime = field(default_factory=datetime.now)
    roles: list[str] = field(default_factory=list)

The pattern-matching guidance is shown against a command-dispatch example:

match command:
    case ["quit"]:
        return "Goodbye!"
    case ["load", filename]:
        return load_file(filename)
    case ["save", filename, *options]:
        return save_file(filename, options)
    case _:
        return "Unknown command"

Best practices cover context managers (@contextmanager wrapping resource acquisition and release in a try/finally), error handling (a custom exception class carrying a message and code, and catching specific exception types like ValueError/IOError rather than a bare except), and async/await (an aiohttp-based async fetch function and an AsyncGenerator-based streaming function). Project structure follows a src/-layout convention (a package directory with core/, services/, utils/ subpackages, a tests/ directory, and pyproject.toml at the project root), configured via pyproject.toml for tools like Poetry or PDM, with example configuration sections for Black (88-char line length), Ruff (88-char line length, selected lint rule codes E, F, I, N, W), and mypy (strict mode enabled).

Use it when writing or reviewing modern Python code - applying type hints, pattern matching, dataclasses, async code, or setting up pyproject.toml tooling. It is not a beginner Python tutorial - it assumes familiarity with the language and focuses on modern (3.10+) idioms and tooling.

Given a Python code-design question, it produces type-hinted signatures such as def greet(name: str) -> str, def process(data: list[dict[str, Any]]) -> dict[str, int], and a str | int | None union-typed parse function, alongside pattern-matching logic, dataclasses, context managers, async functions, or a pyproject.toml configuration block covering Black, Ruff, and mypy sections.

Python developers already comfortable with the language's basics who need to apply Python 3.10+ idioms - type hints, pattern matching, dataclasses, async code - and set up matching pyproject.toml tooling, rather than developers looking to learn Python from scratch.