Getting started with FastAPI 0.159.1

Everything below is taken from the pinned upstream tree at ce6ee83e5411.

Install

pip install fastapi

The smallest application

from fastapi import FastAPI

app = FastAPI()


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

FastAPI is exported from fastapi.applications and re-exported at the package root. Its constructor accepts 37 arguments — every one of them is listed on the configuration page.

The router

from fastapi import APIRouter

router = APIRouter(prefix="/items", tags=["items"])


@router.get("/{item_id}")
async def read_item(item_id: int):
    return {"item_id": item_id}


app.include_router(router)

Path operation decorators

FastAPI and APIRouter both expose the same family of path-operation decorators — 16 HTTP verbs plus api_route and websocket_route. See routing.

Request parameters

from fastapi import Depends, FastAPI, HTTPException

app = FastAPI()


def common_params(q: str | None = None, skip: int = 0):
    return {"q": q, "skip": skip}


@app.get("/items/")
async def read_items(commons: dict = Depends(common_params)):
    return commons

Interactive docs

FastAPI serves the OpenAPI UI at /docs (Swagger UI) and /redoc by default; both paths are constructor arguments and can be turned off.

Where the surface is

• 98 public classes, 92 public methods and 90 public functions were parsed out of the package.
• 156 upstream markdown documentation files were ingested verbatim.
• 78 upstream runnable example groups are catalogued.