from fastapi import FastAPI, Response

app = FastAPI()


@app.get("/headers-and-object/")
def get_headers(response: Response):
    response.headers["X-Cat-Dog"] = "alone in the world"

        .build(),
    )
    newEventSource("text/plain")
    listener.assertOpen()
    listener.assertEvent(null, null, "hey")
    listener.assertClose()
    assertThat(server.takeRequest().headers["Accept"]).isEqualTo("text/plain")
  }

  @Test
  fun setsMissingAccept() {
    server.enqueue(
      MockResponse.Builder()
        .body(
          """
          |data: hey
          |

    return {"item_id": item_id, "item": item}


@app.head("/items/{item_id}")
def head_item(item_id: str):
    return JSONResponse(None, headers={"x-fastapi-item-id": item_id})


@app.options("/items/{item_id}")
def options_item(item_id: str):
    return JSONResponse(None, headers={"x-fastapi-item-id": item_id})


@app.patch("/items/{item_id}")
def patch_item(item_id: str, item: Item):

    userResponse: Response,
    defaultDelay: Int,
  ): Int {
    val header = userResponse.header("Retry-After") ?: return defaultDelay

    // https://tools.ietf.org/html/rfc7231#section-7.1.3
    // currently ignores a HTTP-date, and assumes any non int 0 is a delay
    if (header.matches("\\d+".toRegex())) {
      return Integer.valueOf(header)
    }
    return Integer.MAX_VALUE
  }

  companion object {

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    model_config = {"extra": "forbid"}

    host: str
    save_data: bool
    if_modified_since: str | None = None
    traceparent: str | None = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header()):

from docs_src.response_headers.tutorial002 import app

client = TestClient(app)


def test_path_operation():
    response = client.get("/headers-and-object/")
    assert response.status_code == 200, response.text
    assert response.json() == {"message": "Hello World"}

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    class Config:
        extra = "forbid"

    host: str
    save_data: bool
    if_modified_since: str | None = None
    traceparent: str | None = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header()):

It might also help avoid confusion for new developers that see an unused parameter in your code and could think it's unnecessary.

///

/// info

In this example we use invented custom headers `X-Key` and `X-Token`.

But in real cases, when implementing security, you would get more benefits from using the integrated [Security utilities (the next chapter)](../security/index.md){.internal-link target=_blank}.

///

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    model_config = {"extra": "forbid"}

    host: str
    save_data: bool
    if_modified_since: str | None = None
    traceparent: str | None = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: Annotated[CommonHeaders, Header()]):

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    model_config = {"extra": "forbid"}

    host: str
    save_data: bool
    if_modified_since: Union[str, None] = None
    traceparent: Union[str, None] = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header()):