What is FastAPI, what makes it fast and convenient?

FastAPI is a modern web framework for building APIs with Python, focused on high performance and ease of development.

Why FastAPI is fast:

• Uses an asynchronous server ASGI (e.g., Uvicorn), allowing handling multiple requests simultaneously without blocking.
• Built on Starlette and Pydantic, which are optimized for fast execution.
• Data validation and serialization are done with Pydantic, which uses fast Cython code.

Why it is user-friendly:

• Automatically generates API documentation (Swagger UI, ReDoc).
• Supports Python typing, improving autocompletion and code checking.
• Simple declarative model for describing endpoints with type annotations.
• Built-in support for validation, serialization, OAuth2, CORS, and other standard tasks.

Example of a simple FastAPI application:

from fastapi import FastAPI

app = FastAPI()

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