```console
// Don't run this now, it's just an example 🤓
$ pip install "fastapi[standard]"
---> 100%
```

</div>

That will download a compressed file with the FastAPI code, normally from <a href="https://pypi.org/project/fastapi/" class="external-link" target="_blank">PyPI</a>.

It will also **download** files for other packages that FastAPI depends on.

If you are working with **FastAPI** you don't have to worry about that, because that "first" function will be your *path operation function*, and FastAPI will know how to do the right thing.

But if you want to use `async` / `await` without FastAPI, you can do it as well.

### Write your own async code { #write-your-own-async-code }

# 元数据和文档 URL

你可以在 FastAPI 应用程序中自定义多个元数据配置。

## API 元数据

你可以在设置 OpenAPI 规范和自动 API 文档 UI 中使用的以下字段：

| 参数 | 类型 | 描述 |
|------------|------|-------------|
| `title` | `str` | API 的标题。 |
| `summary` | `str` | API 的简短摘要。 <small>自 OpenAPI 3.1.0、FastAPI 0.99.0 起可用。.</small> |
| `description` | `str` | API 的简短描述。可以使用Markdown。 |
| `version` | `string` | API 的版本。这是您自己的应用程序的版本，而不是 OpenAPI 的版本。例如 `2.5.0` 。 |

from fastapi.testclient import TestClient

from docs_src.path_operation_advanced_configuration.tutorial001_py39 import app

client = TestClient(app)


def test_get():
    response = client.get("/items/")
    assert response.status_code == 200, response.text
    assert response.json() == [{"item_id": "Foo"}]


def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text

/// note | Технические детали

`Header` - это "родственный" класс `Path`, `Query` и `Cookie`. Он также наследуется от того же общего класса `Param`.

Но помните, что когда вы импортируете `Query`, `Path`, `Header` и другие из `fastapi`, на самом деле это функции, которые возвращают специальные классы.

///

/// info | Информация

Чтобы объявить заголовки, важно использовать `Header`, иначе параметры интерпретируются как query-параметры.

///

import importlib

import pytest
from fastapi.testclient import TestClient


@pytest.fixture(
    name="client",
    params=[
        pytest.param("tutorial006_py39"),
        pytest.param("tutorial006_an_py39"),
    ],
)
def get_client(request: pytest.FixtureRequest) -> TestClient:
    mod = importlib.import_module(
        f"docs_src.path_params_numeric_validations.{request.param}"
    )
    return TestClient(mod.app)

import importlib

import pytest
from fastapi.testclient import TestClient


@pytest.fixture(
    name="client",
    params=[
        "tutorial001_py39",
        "tutorial001_an_py39",
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.request_files.{request.param}")

    client = TestClient(mod.app)
    return client


def test_post_form_no_body(client: TestClient):

/// note | Detalhes Técnicos

`Header` é uma classe "irmã" de `Path`, `Query` e `Cookie`. Ela também herda da mesma classe em comum `Param`.

Mas lembre-se que quando você importa `Query`, `Path`, `Header`, e outras de `fastapi`, elas são na verdade funções que retornam classes especiais.

///

/// info | Informação

Para declarar headers, você precisa usar `Header`, caso contrário, os parâmetros seriam interpretados como parâmetros de consulta.

        else:
            use_path = f"{lang}/{path}"
        link = LinkData(
            previous_link=f"https://fastapi.tiangolo.com/{use_path}",
            preview_link=f"{deploy_url}/{use_path}",
        )
        if lang != "en":
            link.en_link = f"https://fastapi.tiangolo.com/{en_path}"
        lang_links.setdefault(lang, []).append(link)

    links: list[LinkData] = []

from fastapi.testclient import TestClient

from docs_src.behind_a_proxy.tutorial002_py39 import app

client = TestClient(app)


def test_main():
    response = client.get("/app")
    assert response.status_code == 200
    assert response.json() == {"message": "Hello World", "root_path": "/api/v1"}


def test_openapi():
    response = client.get("/openapi.json")
    assert response.status_code == 200
    assert response.json() == {