# Parámetros de Header { #header-parameters }

Puedes definir los parámetros de Header de la misma manera que defines los parámetros de `Query`, `Path` y `Cookie`.

## Importar `Header` { #import-header }

Primero importa `Header`:

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[3] *}

## Declarar parámetros de `Header` { #declare-header-parameters }

Si tienes un grupo de **parámetros de header** relacionados, puedes crear un **modelo Pydantic** para declararlos.

Esto te permitirá **reutilizar el modelo** en **múltiples lugares** y también declarar validaciones y metadatos para todos los parámetros al mismo tiempo. 😎

/// note | Nota

Esto es compatible desde la versión `0.115.0` de FastAPI. 🤓

///

///

First, we create a `GzipRequest` class, which will overwrite the `Request.body()` method to decompress the body in the presence of an appropriate header.

If there's no `gzip` in the header, it will not try to decompress the body.

That way, the same route class can handle gzip compressed or uncompressed requests.

{* ../../docs_src/custom_request_and_route/tutorial001_an_py310.py hl[9:16] *}

    en.
    """
    # Enable line numbers during local development to make it easier to highlight
    if lang is None:
        lang = "en"
    lang_path: Path = docs_path / lang
    # Enable line numbers during local development to make it easier to highlight
    args = ["mkdocs", "serve", "--dev-addr", "127.0.0.1:8008"]
    if dirty:
        args.append("--dirty")

///

## Benutzerdefinierte Header { #custom-headers }

Beachten Sie, dass benutzerdefinierte proprietäre Header <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">mittels des Präfix `X-`</a> hinzugefügt werden können.

def test_header_repr_str():
    assert repr(Header("teststr")) == "Header(teststr)"


def test_header_repr_none():
    assert repr(Header(None)) == "Header(None)"


def test_header_repr_ellipsis():
    assert repr(Header(...)) == "Header(PydanticUndefined)"


def test_header_repr_number():
    assert repr(Header(1)) == "Header(1)"


def test_header_repr_list():

from fastapi import FastAPI, Header
from fastapi.testclient import TestClient
from pydantic import BaseModel, Field

app = FastAPI()

# =====================================================================================
# Without aliases


@app.get("/required-str")
async def read_required_str(p: Annotated[str, Header()]):
    return {"p": p}


class HeaderModelRequiredStr(BaseModel):

import pytest
from fastapi import FastAPI, Header
from fastapi.testclient import TestClient
from pydantic import BaseModel, Field

app = FastAPI()

# =====================================================================================
# Without aliases


@app.get("/optional-list-str")
async def read_optional_list_str(
    p: Annotated[Optional[list[str]], Header()] = None,
):
    return {"p": p}

import pytest
from fastapi import FastAPI, Header
from fastapi.testclient import TestClient
from pydantic import BaseModel, Field

app = FastAPI()

# =====================================================================================
# Without aliases


@app.get("/optional-str")
async def read_optional_str(p: Annotated[Optional[str], Header()] = None):
    return {"p": p}

from fastapi import FastAPI, Header
from fastapi.testclient import TestClient
from pydantic import BaseModel, Field

app = FastAPI()

# =====================================================================================
# Without aliases


@app.get("/required-list-str")
async def read_required_list_str(p: Annotated[list[str], Header()]):
    return {"p": p}