在这个例子中，HTTP 头的 `Content-Type` 会被设置成 `application/json`。

并且在 OpenAPI 文档中也会这样记录。

///

/// tip | "小贴士"

`ORJSONResponse` 目前只在 FastAPI 中可用，而在 Starlette 中不可用。

///

## HTML 响应

使用 `HTMLResponse` 来从 **FastAPI** 中直接返回一个 HTML 响应。

* 导入 `HTMLResponse`。
* 将 `HTMLResponse` 作为你的 *路径操作* 的 `response_class` 参数传入。

```Python hl_lines="2 7"
{!../../docs_src/custom_response/tutorial002.py!}

```Python
contents = myfile.file.read()
```

/// note | Detalhes técnicos do `async`

Quando você utiliza métodos assíncronos, o **FastAPI** executa os métodos do arquivo em uma threadpool e espera por eles.

///

/// note | Detalhes técnicos do Starlette

O `UploadFile` do **FastAPI** herda diretamente do `UploadFile` do **Starlette**, mas adiciona algumas funcionalidades necessárias para ser compatível com o **Pydantic**

///

    sent to the client.

    Read more about it in the
    [FastAPI docs for Background Tasks](https://fastapi.tiangolo.com/tutorial/background-tasks/).

    ## Example

    ```python
    from fastapi import BackgroundTasks, FastAPI

    app = FastAPI()


    def write_notification(email: str, message=""):
        with open("log.txt", mode="w") as email_file:

    errors in your code.

    Read more about it in the
    [FastAPI docs for Handling Errors](https://fastapi.tiangolo.com/tutorial/handling-errors/).

    ## Example

    ```python
    from fastapi import FastAPI, HTTPException

    app = FastAPI()

    items = {"foo": "The Foo Wrestlers"}


    @app.get("/items/{item_id}")
    async def read_item(item_id: str):

from fastapi.testclient import TestClient

from docs_src.custom_response.tutorial001 import app

client = TestClient(app)


def test_get_custom_response():
    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

from fastapi.testclient import TestClient

from docs_src.path_operation_advanced_configuration.tutorial002 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

* 상용 어플리케이션에서의 사용.

## Starlette 기능

**FastAPI**는 <a href="https://www.starlette.io/" class="external-link" target="_blank"><strong>Starlette</strong></a>를 기반으로 구축되었으며, 이와 완전히 호환됩니다. 따라서, 여러분이 보유하고 있는 어떤 추가적인 Starlette 코드도 작동할 것입니다.

`FastAPI`는 실제로 `Starlette`의 하위 클래스입니다. 그래서, 여러분이 이미 Starlette을 알고 있거나 사용하고 있으면, 대부분의 기능이 같은 방식으로 작동할 것입니다.

**FastAPI**를 사용하면 여러분은 **Starlette**의 기능 대부분을 얻게 될 것입니다(FastAPI가 단순히 Starlette를 강화했기 때문입니다):

`FastAPI` is a class that inherits directly from `Starlette`.

You can use all the <a href="https://www.starlette.io/" class="external-link" target="_blank">Starlette</a> functionality with `FastAPI` too.

///

### Step 2: create a `FastAPI` "instance"

{* ../../docs_src/first_steps/tutorial001.py hl[3] *}

Here the `app` variable will be an "instance" of the class `FastAPI`.

/// note | "Заметка"

FastAPI понимает, что значение параметра `q` не является обязательным, потому что имеет значение по умолчанию `= None`.

Аннотация `Optional` в `Optional[str]` не используется FastAPI, но помогает вашему редактору лучше понимать ваш код и обнаруживать ошибки.

///

## Без Pydantic

from typing import List, Optional

from fastapi import FastAPI
from fastapi.testclient import TestClient
from pydantic import BaseModel

from .utils import PYDANTIC_V2, needs_pydanticv2


class SubItem(BaseModel):
    subname: str
    sub_description: Optional[str] = None
    tags: List[str] = []
    if PYDANTIC_V2:
        model_config = {"json_schema_serialization_defaults_required": True}


class Item(BaseModel):