This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

## Query Parameters with a Pydantic Model

Declare the **query parameters** that you need in a **Pydantic model**, and then declare the parameter as `Query`:

//// tab | Python 3.10+

/// note

FastAPI will know that the value of `q` is not required because of the default value `= None`.

The `str | None` (Python 3.10+) or `Union` in `Union[str, None]` (Python 3.8+) is not used by FastAPI to determine that the value is not required, it will know it's not required because it has a default value of `= None`.

/// note

**FastAPI** saura que la valeur de `q` n'est pas requise grâce à la valeur par défaut `=None`.

Le type `Optional` dans `Optional[str]` n'est pas utilisé par **FastAPI**, mais sera utile à votre éditeur pour améliorer le support offert par ce dernier et détecter plus facilement des erreurs de type.

///

from fastapi import APIRouter, FastAPI
from fastapi.responses import HTMLResponse, JSONResponse, PlainTextResponse
from fastapi.testclient import TestClient


class OverrideResponse(JSONResponse):
    media_type = "application/x-override"


app = FastAPI()
router_a = APIRouter()
router_a_a = APIRouter()
router_a_b_override = APIRouter()  # Overrides default class
router_b_override = APIRouter()  # Overrides default class

    Set,
    Type,
    Union,
    cast,
)
from weakref import WeakKeyDictionary

import fastapi
from fastapi._compat import (
    PYDANTIC_V2,
    BaseConfig,
    ModelField,
    PydanticSchemaGenerationError,
    Undefined,
    UndefinedType,
    Validator,
    lenient_issubclass,
)
from fastapi.datastructures import DefaultPlaceholder, DefaultType
from pydantic import BaseModel, create_model

from fastapi import FastAPI
from fastapi.openapi.docs import (
    get_redoc_html,
    get_swagger_ui_html,
    get_swagger_ui_oauth2_redirect_html,
)
from fastapi.staticfiles import StaticFiles

app = FastAPI(docs_url=None, redoc_url=None)

app.mount("/static", StaticFiles(directory="static"), name="static")


@app.get("/docs", include_in_schema=False)
async def custom_swagger_ui_html():
    return get_swagger_ui_html(

## Características Adicionales

El [Tutorial - Guía de Usuario](../tutorial/index.md){.internal-link target=_blank} principal debe ser suficiente para darte un paseo por todas las características principales de **FastAPI**

En las secciones siguientes verás otras opciones, configuraciones, y características adicionales.

/// tip | Consejo

Las próximas secciones **no son necesariamente "avanzadas"**.

```JSON
{"item_id":3}
```

/// check

Notice that the value your function received (and returned) is `3`, as a Python `int`, not a string `"3"`.

So, with that type declaration, **FastAPI** gives you automatic request <abbr title="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>.

///

## Data validation

```JSON
{"item_id":3}
```

/// check | Revisa

Observa que el valor que recibió (y devolvió) tu función es `3`, como un Python `int`, y no un string `"3"`.

Entonces, con esa declaración de tipos **FastAPI** te da <abbr title="convertir el string que viene de un HTTP request a datos de Python">"parsing"</abbr> automático del request.

///

## Validación de datos

**Gunicorn** ist hauptsächlich ein Anwendungsserver, der den **WSGI-Standard** verwendet. Das bedeutet, dass Gunicorn Anwendungen wie Flask und Django ausliefern kann. Gunicorn selbst ist nicht mit **FastAPI** kompatibel, da FastAPI den neuesten **<a href="https://asgi.readthedocs.io/en/latest/" class="external-link" target="_blank">ASGI-Standard</a>** verwendet.