# 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}
        »»»

Aber jedes Mal, wenn wir ausführen:

```Python
Settings()
```

    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

In versions lower than `0.65.2`, FastAPI would try to read the request payload as JSON even if the `content-type` header sent was not set to `application/json` or a compatible JSON media type (e.g. `application/geo+json`).

So, a request with a content type of `text/plain` containing JSON data would be accepted and the JSON data would be extracted.