Python FastAPI Patterns Project Structure Basic Setup Pydantic Models Route Organization Dependency Injection Async Patterns Error Handling Settings Management Middleware Testing Best Practices 1. Use type hints everywhere for auto-documentation 2. Validate at boundaries with Pydantic models 3. Inject dependencies for testability 4. Handle errors consistently with custom exceptions 5. Use async/await for I/O operations 6. Keep routes thin - business logic in services 7. Document with OpenAPI annotations ---