## Declare `Header` parameters { #declare-header-parameters }

Then declare the header parameters using the same structure as with `Path`, `Query` and `Cookie`.

You can define the default value as well as all the extra validation or annotation parameters:

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[9] *}

/// note | Technical Details

Pero aún necesitas usar `Path` para el parámetro de path `item_id`. Y no quieres usar `Annotated` por alguna razón.

Python se quejará si pones un valor con un "default" antes de un valor que no tenga un "default".

Pero puedes reordenarlos y poner el valor sin un default (el parámetro de query `q`) primero.

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(user_agent: str | None = Header(default=None)):

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(x_token: list[str] | None = Header(default=None)):

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: list[str] | None = Query(default=None)):
    query_items = {"q": q}

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: str | None = Query(
        default=None, min_length=3, max_length=50, pattern="^fixedquery$"
    ),
):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

     *
     * @param message The message describing the problem, may be {@code null}.
     * @param severity The severity level of the problem, may be {@code null} to default to
     *            {@link ModelProblem.Severity#ERROR}.
     * @param source The source of the problem, may be {@code null}.
     * @param lineNumber The one-based index of the line containing the error or {@code -1} if unknown.

import org.apache.maven.artifact.repository.layout.ArtifactRepositoryLayout;

@Deprecated
public interface ArtifactRepositoryFactory {

    String DEFAULT_LAYOUT_ID = "default";

    String LOCAL_REPOSITORY_ID = "local";

    @Deprecated
    ArtifactRepositoryLayout getLayout(String layoutId) throws UnknownRepositoryLayoutException;

    @Deprecated

 */
package org.apache.maven.lifecycle.providers.packaging;

import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Singleton;

/**
 * {@code ear} packaging plugins bindings provider for {@code default} lifecycle.
 */
@Named("ear")
@Singleton
public final class EarLifecycleMappingProvider extends AbstractLifecycleMappingProvider {
    // START SNIPPET: ear
    private static final String[] BINDINGS = {

from fastapi import FastAPI, Query
from fastapi.testclient import TestClient

app = FastAPI()


@app.get("/items/")
def read_items(q: list[int] = Query(default=None)):
    return {"q": q}


client = TestClient(app)


def test_multi_query():
    response = client.get("/items/?q=5&q=6")
    assert response.status_code == 200, response.text
    assert response.json() == {"q": [5, 6]}


def test_multi_query_incorrect():