FastAPI Hello World: Build Your Own Tiny API

The practice API on this site is built with FastAPI. You can build the smallest possible version yourself in a minute.

Install

pip install fastapi uvicorn

Write main.py

from fastapi import FastAPI

app = FastAPI()

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

Run it

uvicorn main:app --reload

Open http://127.0.0.1:8000/hello in your browser. FastAPI also builds a page at /docs where you can try every endpoint with a button.

Your turn

Add a second route, like /names/{id}, that returns one name from a list. Compare it with the live practice API.

Challenge

Add GET /names/{id} to your app. It should return one name, and a 404 with a helpful message when the id does not exist.

Show the answer

Look the id up in a list, and raise HTTPException with status 404 when nothing matches. Then open /docs on your own app and press the button.

from fastapi import FastAPI, HTTPException

app = FastAPI()
NAMES = [{"id": 1, "name": "Ada"}, {"id": 2, "name": "Grace"}]


@app.get("/names/{name_id}")
def one_name(name_id: int):
    for n in NAMES:
        if n["id"] == name_id:
            return n
    raise HTTPException(status_code=404, detail="No name with that id.")