# Header-параметры

Вы можете определить параметры заголовка таким же образом, как вы определяете параметры `Query`, `Path` и `Cookie`.

## Импорт `Header`

Сперва импортируйте `Header`:

//// tab | Python 3.10+

```Python hl_lines="3"
{!> ../../docs_src/header_params/tutorial001_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="3"
{!> ../../docs_src/header_params/tutorial001_an_py39.py!}
```

# Header-Parameter

So wie `Query`-, `Path`-, und `Cookie`-Parameter können Sie auch <abbr title='Header – Kopfzeilen, Header, Header-Felder: Schlüssel-Wert-Metadaten, die vom Client beim Request, und vom Server bei der Response gesendet werden'>Header</abbr>-Parameter definieren.

## `Header` importieren

Importieren Sie zuerst `Header`:

//// tab | Python 3.10+

```Python hl_lines="3"
{!> ../../docs_src/header_params/tutorial001_an_py310.py!}
```

        @app.get("/cookie_example/")
        def cookie_example(
            data: Union[str, None] = Cookie(
                default=None,
                example="cookie1",
            ),
        ):
            return data

    @app.get("/cookie_examples/")
    def cookie_examples(
        data: Union[str, None] = Cookie(
            default=None,
            examples=["cookie1", "cookie2"],
        ),
    ):

        "components": {
            "securitySchemes": {
                "APIKeyCookie": {
                    "type": "apiKey",
                    "name": "key",
                    "in": "cookie",
                    "description": "An API Cookie Key",
                }
            }
        },

```

////

/// note | "技术细节"

`Header` 是 `Path`、`Query`、`Cookie` 的**兄弟类**，都继承自共用的 `Param` 类。

注意，从 `fastapi` 导入的 `Query`、`Path`、`Header` 等对象，实际上是返回特殊类的函数。

///

/// info | "说明"

必须使用 `Header` 声明 header 参数，否则该参数会被解释为查询参数。

///

## 自动转换

`Header` 比 `Path`、`Query` 和 `Cookie` 提供了更多功能。

大部分标准请求头用**连字符**分隔，即**减号**（`-`）。

但是 `user-agent` 这样的变量在 Python 中是无效的。

from typing import Union

from fastapi import Cookie, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Cookies(BaseModel):
    session_id: str
    fatebook_tracker: Union[str, None] = None
    googall_tracker: Union[str, None] = None


@app.get("/items/")
async def read_items(cookies: Cookies = Cookie()):

from typing import Annotated

from fastapi import Cookie, FastAPI
from pydantic import BaseModel

app = FastAPI()


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

    session_id: str
    fatebook_tracker: str | None = None
    googall_tracker: str | None = None


@app.get("/items/")
async def read_items(cookies: Annotated[Cookies, Cookie()]):

from typing import Union

from fastapi import Cookie, FastAPI
from pydantic import BaseModel

app = FastAPI()


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

    session_id: str
    fatebook_tracker: Union[str, None] = None
    googall_tracker: Union[str, None] = None


@app.get("/items/")
async def read_items(cookies: Cookies = Cookie()):

from typing import Union

from fastapi import Cookie, FastAPI
from pydantic import BaseModel
from typing_extensions import Annotated

app = FastAPI()


class Cookies(BaseModel):
    session_id: str
    fatebook_tracker: Union[str, None] = None
    googall_tracker: Union[str, None] = None


@app.get("/items/")
async def read_items(cookies: Annotated[Cookies, Cookie()]):

from typing import Annotated, Union

from fastapi import Cookie, FastAPI
from pydantic import BaseModel

app = FastAPI()


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

    session_id: str
    fatebook_tracker: Union[str, None] = None
    googall_tracker: Union[str, None] = None


@app.get("/items/")
async def read_items(cookies: Annotated[Cookies, Cookie()]):