Fastapi Expert

FastAPI Expert

Goal: Build high-performance, type-safe, and self-documenting APIs using modern Python.

1. Core Principles

• Type Hints: Use standard Python type hints everywhere.
• Pydantic Models: Separation of concerns.
  • UserCreate (Input)
  • UserUpdate (Partial Input)
  • UserResponse (Output - NO passwords!)
• Dependency Injection: Use Depends for DB sessions, auth users, and reusable logic.

2. API Structure

app/
├── api/
│   ├── v1/
│   │   ├── endpoints/
│   │   │   ├── users.py
│   │   │   └── items.py
│   │   └── router.py
│   └── deps.py         # Dependencies (get_current_user, get_db)
├── core/
│   ├── config.py       # Pydantic Settings
│   └── security.py     # JWT logic, password hashing
├── db/
│   ├── base.py
│   └── session.py
├── models/             # SQLAlchemy / Tortoise / SQLModel models
├── schemas/            # Pydantic models
└── main.py

3. Database Patterns (SQLAlchemy 2.0 / SQLModel)

• Async Session: Use AsyncSession for non-blocking I/O.
• Allembic: Mandatory for migrations. Never use create_all in production.
• Context Managers: Ensure DB sessions are closed.

async def get_db():
    async with AsyncSessionLocal() as session:
        yield session

4. Authentication & Security

• OAuth2: Use OAuth2PasswordBearer for strict spec compliance.
• JWT: Stateless auth. Keep access tokens short-lived (15m), refresh tokens long (7d).
• Hashing: Use passlib with bcrypt or argon2.

5. Performance Tips

• Uvicorn: Run with uvicorn main:app --workers 4 --loop uvloop.
• Async/Await: properly await I/O bound operations. Don't block the event loop with heavy CPU tasks (use run_in_threadpool).
• JSON Serialization: Use orjson for faster JSON parsing/encoding.

6. Testing (Pytest)

• AsyncClient: Use httpx.AsyncClient for testing routes.
• Override Dependencies: Use app.dependency_overrides to mock DB or Auth during tests.

async def test_create_item(async_client: AsyncClient):
    response = await async_client.post("/items/", json={"name": "Test"})
    assert response.status_code == 200

Source: Meet6338-X/MeetKitAI — distributed by TomeVault.