Aber jedes Mal, wenn wir ausführen:

```Python
Settings()
```

# Usando Dataclasses { #using-dataclasses }

FastAPI está construido sobre **Pydantic**, y te he estado mostrando cómo usar modelos de Pydantic para declarar requests y responses.

Pero FastAPI también soporta el uso de <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> de la misma manera:

{* ../../docs_src/dataclasses_/tutorial001_py310.py hl[1,6:11,18:19] *}

Example:

    Source (English):

        «««
        [Create Pull Requests](help-fastapi.md#create-a-pull-request){.internal-link target=_blank}
        »»»

    Result (German):

        «««
        [Pull Requests erzeugen](help-fastapi.md#create-a-pull-request){.internal-link target=_blank}
        »»»

    else:
        actual_response_class = response_class

    async def app(request: Request) -> Response:
        response: Union[Response, None] = None
        file_stack = request.scope.get("fastapi_middleware_astack")
        assert isinstance(file_stack, AsyncExitStack), (
            "fastapi_middleware_astack not found in request scope"
        )

        # Extract endpoint context for error messages

* Validate that there is an `item_id` in the path for `GET` and `PUT` requests.
* Validate that the `item_id` is of type `int` for `GET` and `PUT` requests.
    * If it is not, the client will see a useful, clear error.
* Check if there is an optional query parameter named `q` (as in `http://127.0.0.1:8000/items/foo?q=somequery`) for `GET` requests.
    * As the `q` parameter is declared with `= None`, it is optional.

from pytest import MonkeyPatch


@pytest.fixture(name="app", params=[pytest.param("tutorial001_py39")])
def get_app(request: pytest.FixtureRequest, monkeypatch: MonkeyPatch):
    monkeypatch.setenv("ADMIN_EMAIL", "******@****.***")
    mod = importlib.import_module(f"docs_src.settings.{request.param}")
    return mod.app


def test_settings(app):
    client = TestClient(app)
    response = client.get("/info")

* «the payload»: «die Payload»
* «the performance»: NOT «die Performance»
* «the query»: «die Query»
* «the recap»: «die Zusammenfassung»
* «the request» (what the client sends to the server): «der Request»
* «the request body»: «der Requestbody»
* «the request bodies» (plural): «die Requestbodys»
* «the response» (what the server sends back to the client): «die Response»
* «the return type»: «der Rückgabetyp»

@pytest.fixture(
    name="client",
    params=[
        "tutorial001_py39",
        "tutorial003_py39",
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.first_steps.{request.param}")
    client = TestClient(mod.app)
    return client


@pytest.mark.parametrize(
    "path,expected_status,expected_response",
    [

        Doc(
            """
            By default, after a dependency is called the first time in a request, if
            the dependency is declared again for the rest of the request (for example
            if the dependency is needed by several dependencies), the value will be
            re-used for the rest of the request.

            Set `use_cache` to `False` to disable this behavior and ensure the

@pytest.fixture(
    name="client",
    params=[
        pytest.param("tutorial002_py39"),
        pytest.param("tutorial002_py310", marks=needs_py310),
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.dataclasses_.{request.param}")

    client = TestClient(mod.app)
    client.headers.clear()
    return client


def test_get_item(client: TestClient):