Python Development Project Setup Modern Python Project Structure my-project/ ├── src/ │ └── my_project/ │ ├── init.py │ ├── main.py │ └── utils.py ├── tests/ │ ├── init.py │ └── test_main.py ├── pyproject.toml ├── README.md └── .gitignore
pyproject.toml [ project ] name = "my-project" version = "0.1.0" requires-python = ">=3.12" dependencies = [ "fastapi>=0.100.0", "pydantic>=2.0", ]
[ project.optional-dependencies ] dev = [ "pytest>=7.0", "ruff>=0.1.0", "mypy>=1.0", ]
[ tool.ruff ] line-length = 88 select = ["E", "F", "I", "N", "W"]
[ tool.mypy ] strict = true
Type Hints from typing import TypeVar, Generic from collections.abc import Sequence
T = TypeVar('T')
def process_items(items: Sequence[str]) -> list[str]: return [item.upper() for item in items]
class Repository(Generic[T]): def get(self, id: int) -> T | None: ... def save(self, item: T) -> T: ...
Async Patterns import asyncio from collections.abc import AsyncIterator
async def fetch_all(urls: list[str]) -> list[dict]: async with aiohttp.ClientSession() as session: tasks = [fetch_one(session, url) for url in urls] return await asyncio.gather(*tasks)
async def stream_data() -> AsyncIterator[bytes]: async with aiofiles.open('large_file.txt', 'rb') as f: async for chunk in f: yield chunk
FastAPI Patterns from fastapi import FastAPI, Depends, HTTPException from pydantic import BaseModel
app = FastAPI()
class UserCreate(BaseModel): email: str name: str
class UserResponse(BaseModel): id: int email: str name: str
@app.post("/users", response_model=UserResponse) async def create_user( user: UserCreate, db: Database = Depends(get_db) ) -> UserResponse: result = await db.users.create(user.model_dump()) return UserResponse(**result)
Testing import pytest from unittest.mock import AsyncMock, patch
@pytest.fixture def mock_db(): db = AsyncMock() db.users.get.return_value = {"id": 1, "name": "Test"} return db
@pytest.mark.asyncio async def test_get_user(mock_db): result = await get_user(1, db=mock_db) assert result["name"] == "Test" mock_db.users.get.assert_called_once_with(1)
Best Practices Use ruff for linting and formatting Use mypy with strict mode Prefer pathlib.Path over os.path Use dataclasses or Pydantic for data structures Use asyncio for I/O-bound operations Use contextlib.asynccontextmanager for async resources