* Traiter des données :
    * Par exemple, si vous recevez un fichier qui doit passer par un traitement lent, vous pouvez retourner une réponse «Accepted» (HTTP 202) puis faire le traitement en arrière-plan.


## Utiliser `BackgroundTasks`

    items["foo"] = {"name": "Fighters"}
    items["bar"] = {"name": "Tenders"}


@app.get("/items/{item_id}")
async def read_items(item_id: str):
    return items[item_id]


def test_read_items():
    with TestClient(app) as client:
        response = client.get("/items/foo")
        assert response.status_code == 200

        assert items == {"foo": {"name": "Fighters"}, "bar": {"name": "Tenders"}}

        response = client.get("/items/foo")
        assert response.status_code == 200
        assert response.json() == {"name": "Fighters"}

        # After the requests is done, the items are still there
        assert items == {"foo": {"name": "Fighters"}, "bar": {"name": "Tenders"}}

    assert response.json() == {"name": "Bar", "description": "The Bar fighters"}


def test_read_item_public_data(client: TestClient):
    response = client.get("/items/bar/public")
    assert response.status_code == 200, response.text
    assert response.json() == {
        "name": "Bar",
        "description": "The Bar fighters",
        "price": 62,
    }


def test_openapi_schema(client: TestClient):

    assert response.json() == {"name": "Bar", "description": "The Bar fighters"}


def test_read_item_public_data(client: TestClient):
    response = client.get("/items/bar/public")
    assert response.status_code == 200, response.text
    assert response.json() == {
        "name": "Bar",
        "description": "The Bar fighters",
        "price": 62,
    }


def test_openapi_schema(client: TestClient):

# Démarrage

Le fichier **FastAPI** le plus simple possible pourrait ressembler à cela  :

{* ../../docs_src/first_steps/tutorial001.py *}

Copiez ce code dans un fichier nommé `main.py`.

Démarrez le serveur :

<div class="termy">

```console
$ uvicorn main:app --reload

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)

from fastapi import FastAPI

app = FastAPI()

items = {}


@app.on_event("startup")
async def startup_event():
    items["foo"] = {"name": "Fighters"}
    items["bar"] = {"name": "Tenders"}


@app.get("/items/{item_id}")
async def read_items(item_id: str):

from typing import Annotated, Union

from fastapi import Body, FastAPI, status
from fastapi.responses import JSONResponse

app = FastAPI()

items = {"foo": {"name": "Fighters", "size": 6}, "bar": {"name": "Tenders", "size": 3}}


@app.put("/items/{item_id}")
async def upsert_item(
    item_id: str,
    name: Annotated[Union[str, None], Body()] = None,
    size: Annotated[Union[int, None], Body()] = None,
):
    if item_id in items:

class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float = 10.5


items = {
    "foo": {"name": "Foo", "price": 50.2},
    "bar": {"name": "Bar", "description": "The Bar fighters", "price": 62, "tax": 20.2},
    "baz": {
        "name": "Baz",
        "description": "There goes my baz",
        "price": 50.2,
        "tax": 10.5,
    },
}


@app.get(

    name: str
    description: Union[str, None] = None
    price: float
    tax: float = 10.5


items = {
    "foo": {"name": "Foo", "price": 50.2},
    "bar": {"name": "Bar", "description": "The Bar fighters", "price": 62, "tax": 20.2},
    "baz": {
        "name": "Baz",
        "description": "There goes my baz",
        "price": 50.2,
        "tax": 10.5,
    },
}


@app.get(