}

app = FastAPI()


class Item(BaseModel):
    id: str
    title: str
    description: str | None = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: str = Header()):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item_id not in fake_db:

}

app = FastAPI()


class Item(BaseModel):
    id: str
    title: str
    description: Union[str, None] = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item_id not in fake_db:

from fastapi.testclient import TestClient

from .app.main import app

client = TestClient(app)


def test_post_a():
    data = {"a": 2, "b": "foo"}
    response = client.post("/a/compute", json=data)
    assert response.status_code == 200, response.text
    data = response.json()


def test_post_a_invalid():
    data = {"a": "bar", "b": "foo"}
    response = client.post("/a/compute", json=data)

arjwilliams <******@****.***> 1713477419 +0100

Sebastián Ramírez <******@****.***> 1561743316 +0200

Sebastián Ramírez <******@****.***> 1641564691 +0100

Sebastián Ramírez <******@****.***> 1698179166 +0400

from ...utils import needs_py310


@needs_py310
def test_app():
    from docs_src.app_testing.app_b_an_py310 import test_main

    test_main.test_create_existing_item()
    test_main.test_create_item()
    test_main.test_create_item_bad_token()
    test_main.test_read_nonexistent_item()
    test_main.test_read_item()

=== "Uvicorn"

    <div class="termy">

    ```console
    $ uvicorn main:app --host 0.0.0.0 --port 80

    <span style="color: green;">INFO</span>:     Uvicorn running on http://0.0.0.0:80 (Press CTRL+C to quit)
    ```

    </div>

=== "Hypercorn"

    <div class="termy">

    ```console
    $ hypercorn main:app --bind 0.0.0.0:80

    Running on 0.0.0.0:8080 over http (CTRL + C to quit)
    ```

### The main app file

Now we create a dependency that returns a new `config.Settings()`.

=== "Python 3.9+"

    ```Python hl_lines="6  12-13"
    {!> ../../../docs_src/settings/app02_an_py39/main.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="6  12-13"
    {!> ../../../docs_src/settings/app02_an/main.py!}
    ```

=== "Python 3.8+ non-Annotated"