FastAPI FoundationsLesson 1.1

What is FastAPI and why is it faster than Flask and Django REST

ASGI vs WSGI, Starlette base, Pydantic integration, automatic OpenAPI docs, performance benchmarks, type hint driven development

FastAPI vs Flask vs Django REST

FastAPI is a modern Python web framework built on Starlette (ASGI) and Pydantic. Unlike Flask or Django REST Framework, it uses Python type hints to drive request validation, serialization, and automatic OpenAPI documentation — all with zero extra configuration.

WSGI vs ASGI

Flask and Django REST use WSGI — a synchronous interface. Each request blocks a thread. FastAPI runs on ASGI, which supports async/await natively. Under load, ASGI servers like Uvicorn handle thousands of concurrent connections without spawning new threads.

What you get for free

Declare a route with type hints, and FastAPI automatically: validates incoming data, returns meaningful 422 errors when input is wrong, and generates interactive Swagger UI at /docs and ReDoc at /redoc.

Install and run your first app

# Install
pip install fastapi uvicorn

# main.py
from fastapi import FastAPI

app = FastAPI()

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

# Run
uvicorn main:app --reload

Open http://127.0.0.1:8000/docs — your API is already documented. The --reload flag restarts the server on file changes during development.