fastapi-development_skill

Overview

This skill teaches modern Python API development with FastAPI, focusing on async patterns, Pydantic validation, dependency injection, security, and production deployment. It equips developers to build high-performance, type-safe APIs with automatic OpenAPI docs and robust testing and deployment workflows.

How this skill works

The skill walks through building a FastAPI app, defining Pydantic models for validation and serialization, and organizing endpoints with routers and dependencies. It covers when to use async vs sync endpoints, async database patterns, authentication (OAuth2/JWT), background tasks, and deployment best practices with ASGI servers. Practical examples show routing, query/path validation, response models, and dependency injection patterns for reusable logic.

When to use it

• Building RESTful APIs for web, mobile, or microservices
• Creating high-performance asynchronous backends with async I/O
• Adding automatic OpenAPI/Swagger documentation and typed request/response validation
• Implementing OAuth2/JWT authentication or API-key security
• Integrating SQL or NoSQL databases with sync or async drivers
• Migrating from Flask or Django REST Framework to a type-safe framework

Best practices

• Prefer async def for I/O-bound work and def for CPU-bound or sync libraries
• Use Pydantic models for request/response schemas and enable orm_mode for DB models
• Factor reusable logic into Depends dependencies and class-based dependencies for pagination/auth
• Validate query/path parameters with Query and Path for clear error messages and docs
• Run FastAPI under a production ASGI server (uvicorn/gunicorn) and handle startup/shutdown events for DB connections
• Write tests using TestClient and include async tests for endpoints relying on async drivers

Example use cases

• Public REST API with typed endpoints, pagination, and search filters
• Microservice exposing JSON APIs with async DB access and concurrent external API calls
• Authenticated user service with OAuth2 password flow, JWT tokens, and password hashing
• Real-time features using WebSocket endpoints alongside REST routes
• Migration of endpoints from Flask/Django to FastAPI with improved validation and autogenerated docs