fastapi

fastapi

Modern Python web framework built on Starlette and Pydantic for high-performance async APIs.

Core Concepts

• Async endpoints: define routes with async def, FastAPI handles concurrency via asyncio
• Pydantic v2 models: request/response validation with BaseModel, automatic JSON Schema generation
• Dependency Injection: Depends() resolves reusable components across route handlers
• OpenAPI/Swagger: auto-generated interactive docs at /docs and /redoc from type hints

Common Patterns

• Background tasks: BackgroundTasks for post-response operations like email or logging
• CORS middleware: CORSMiddleware with allow_origins for cross-origin browser requests
• WebSocket: WebSocket endpoint with websocket.accept() for real-time bidirectional communication
• Router modularity: APIRouter with prefix and tags to organize endpoints by domain