Python Pro

Python Pro: Modern Development

This skill defines the gold standard for Python development in the 2024+ era. Move beyond legacy practices (requirements.txt, setup.py, untyped code) to a robust, production-ready workflow.

1. Modern Tooling Stack

Setup Command (The "Holy Trinity")

# Initialize with uv
uv init my-project
cd my-project

# Add standard dev dependencies
uv add --dev ruff mypy pytest pytest-cov

2. Project Structure (The src Layout)

ALWAYS use the src layout. It prevents accidental imports from the project root and ensures testing against the installed package.

my-project/
├── pyproject.toml       # Single config file for EVERYTHING
├── uv.lock              # Lock file (determinism)
├── README.md
├── .python-version      # Managed by uv
├── src/
│   └── my_package/
│       ├── __init__.py
│       └── main.py
└── tests/
    ├── __init__.py
    └── test_main.py

3. Configuration (pyproject.toml)

Centralize config. Avoid redundant .flake8, pytest.ini, or .coveragerc.

[project]
name = "my-project"
version = "0.1.0"
requires-python = ">=3.10"
dependencies = [
    "pydantic>=2.0",
]

[tool.ruff]
line-length = 88
target-version = "py310"

[tool.ruff.lint]
select = ["E", "F", "I", "UP", "B", "T20"] # I=Isort, UP=PyUpgrade, B=Bugbear, T20=Check prints
ignore = []

[tool.mypy]
strict = true
python_version = "3.10"
ignore_missing_imports = true

[tool.pytest.ini_options]
testpaths = ["tests"]
pythonpath = ["src"]
addopts = "-ra -q --cov=my_package --cov-report=term-missing"

4. Modern Idioms & Best Practices

A. Strict Typing

Write strict types. Avoid Any where possible.

from typing import Sequence, Mapping

def process(items: Sequence[int]) -> Mapping[str, int]:
    return {"total": sum(items)}

B. Pydantic V2

Use BaseModel for data structures and Field for validation.

from pydantic import BaseModel, Field, EmailStr

class User(BaseModel):
    id: int = Field(gt=0)
    name: str = Field(min_length=2)
    email: EmailStr

C. Resource Management (pathlib & contextlib)

from pathlib import Path
from contextlib import suppress

data_path = Path("data/raw.json")
with suppress(FileNotFoundError):
    content = data_path.read_text()

D. AsyncIO Patterns

import asyncio
import aiohttp

async def fetch(url: str) -> dict:
    async with aiohttp.ClientSession() as session:
        async with session.get(url) as resp:
            return await resp.json()

5. Testing & CI/CD

A. Advanced Pytest

Use fixtures and marks.

import pytest

@pytest.fixture
def sample_user():
    return User(id=1, name="Dev", email="dev@example.com")

@pytest.mark.asyncio
async def test_async_fetch():
    # ...

B. CI Pipeline (GitHub Actions)

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Install uv
        uses: astral-sh/setup-uv@v3
      - name: Run tests
        run: uv run pytest

Checklist for Implementation

1. Typing: All public APIs fully typed.
2. Linting: uv run ruff check . passes.
3. Formatting: uv run ruff format . applied.
4. Testing: Minimum 80% coverage recommended.
5. Logging: Use logging.getLogger(__name__).