Building REST APIs with FastAPI

FastAPI has quickly become one of the most popular Python frameworks for building APIs. It combines the simplicity of Python with modern features like automatic OpenAPI documentation, type hints, and async support.

Why FastAPI?

FastAPI offers several advantages over traditional frameworks:

• Performance: One of the fastest Python frameworks available
• Type Safety: Built-in support for Python type hints
• Automatic Documentation: Swagger UI and ReDoc generated automatically
• Async Support: Native support for async/await patterns

Getting Started

First, install FastAPI and an ASGI server:

pip install fastapi uvicorn

Create a simple API:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
async def root():
    return {"message": "Hello World"}

@app.get("/items/{item_id}")
async def read_item(item_id: int, q: str | None = None):
    return {"item_id": item_id, "q": q}

Request Validation with Pydantic

FastAPI uses Pydantic for data validation:

from pydantic import BaseModel

class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None

@app.post("/items/")
async def create_item(item: Item):
    return item

Dependency Injection

FastAPI has a powerful dependency injection system:

from fastapi import Depends

async def get_db():
    db = Database()
    try:
        yield db
    finally:
        db.close()

@app.get("/users/")
async def read_users(db: Database = Depends(get_db)):
    return db.get_users()

Conclusion

FastAPI provides an excellent developer experience while maintaining high performance. Its automatic documentation and type safety make it ideal for building production-ready APIs.