FastAPI Quickstart

Install FastAPI along with Uvicorn, the recommended ASGI server:

pip install fastapi uvicorn

Successfully installed fastapi-0.109.0 uvicorn-0.27.0 ...

💡 Use pip install "fastapi[standard]" for additional features like form handling and file uploads.

Create a new file called main.py:

# main.py
from fastapi import FastAPI
app = FastAPI()
@app.get("/")
def read_root():
return {“message”: “Hello, World!”}
@app.get("/items/{item_id}")
def read_item(item_id: int, q: str = None):
return {“item_id”: item_id, “query”: q}

📝 FastAPI uses Python type hints for automatic validation and documentation. The item_id: int ensures the parameter is converted to an integer.

Start the development server with auto-reload:

uvicorn main:app --reload

INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [28720] using StatReload
INFO:     Started server process [28722]
INFO:     Waiting for application startup.
INFO:     Application startup complete.

💡 The --reload flag enables auto-reload on code changes. Perfect for development!

Test with curl:

curl http://127.0.0.1:8000/

{"message":"Hello, World!"}

Test the dynamic endpoint:

curl "http://127.0.0.1:8000/items/42?q=test"

{"item_id":42,"query":"test"}

Explore the Interactive API Documentation:

FastAPI automatically generates interactive API documentation. Open your browser and visit:

✨ This is Swagger UI - you can test your API directly from the browser! Click "Try it out" on any endpoint.

Alternative documentation (ReDoc):