## Using `BackgroundTasks` { #using-backgroundtasks }

First, import `BackgroundTasks` and define a parameter in your *path operation function* with a type declaration of `BackgroundTasks`:

{* ../../docs_src/background_tasks/tutorial001_py310.py hl[1,13] *}

**FastAPI** will create the object of type `BackgroundTasks` for you and pass it as that parameter.

from collections.abc import Callable
from typing import Annotated, Any

from annotated_doc import Doc
from starlette.background import BackgroundTasks as StarletteBackgroundTasks
from typing_extensions import ParamSpec

P = ParamSpec("P")


class BackgroundTasks(StarletteBackgroundTasks):
    """
    A collection of background tasks that will be called after a response has been
    sent to the client.

    Read more about it in the

* 处理数据：
    * 例如，假设您收到的文件必须经过一个缓慢的过程，您可以返回一个"Accepted"(HTTP 202)响应并在后台处理它。

## 使用 `BackgroundTasks` { #using-backgroundtasks }

首先导入 `BackgroundTasks` 并在 *路径操作函数* 中使用类型声明 `BackgroundTasks` 定义一个参数：

{* ../../docs_src/background_tasks/tutorial001_py310.py hl[1,13] *}

**FastAPI** 会创建一个 `BackgroundTasks` 类型的对象并作为该参数传入。

## 创建一个任务函数 { #create-a-task-function }

创建要作为后台任务运行的函数。

它只是一个可以接收参数的标准函数。

    assert resp.status_code == 200
    assert resp.json() == {"path": "/", "user_agent": "test-agent"}


# Tests for BackgroundTasks type hint with Depends
def test_background_tasks_with_depends_annotated():
    """BackgroundTasks type hint should work with Annotated[BackgroundTasks, Depends(...)]."""
    app = FastAPI()
    task_results = []

    def background_task(message: str):

* データ処理:
    * たとえば、時間のかかる処理を必要とするファイル受信時には、「Accepted」(HTTP 202) のレスポンスを返し、バックグラウンドで処理できます。

## `BackgroundTasks` の使用 { #using-backgroundtasks }

まず初めに、`BackgroundTasks` をインポートし、`BackgroundTasks` の型宣言と共に、*path operation function* のパラメーターを定義します:

{* ../../docs_src/background_tasks/tutorial001_py310.py hl[1,13] *}

**FastAPI** は、`BackgroundTasks` 型のオブジェクトを作成し、そのパラメーターに渡します。

## タスク関数の作成 { #create-a-task-function }

* 處理資料：
    * 例如，收到一個需要經過較慢處理流程的檔案時，你可以先回應「Accepted」（HTTP 202），再在背景處理該檔案。

## 使用 `BackgroundTasks` { #using-backgroundtasks }

首先，匯入 `BackgroundTasks`，並在你的路徑操作函式中定義一個型別為 `BackgroundTasks` 的參數：

{* ../../docs_src/background_tasks/tutorial001_py310.py hl[1,13] *}

**FastAPI** 會為你建立 `BackgroundTasks` 物件，並以該參數傳入。

## 建立任務函式 { #create-a-task-function }

建立一個作為背景任務執行的函式。

它只是個可接收參數的一般函式。

# Background Tasks - `BackgroundTasks`

You can declare a parameter in a *path operation function* or dependency function with the type `BackgroundTasks`, and then you can use it to schedule the execution of background tasks after the response is sent.

You can import it directly from `fastapi`:

```python
from fastapi import BackgroundTasks
```

__version__ = "0.135.3"

from starlette import status as status

from .applications import FastAPI as FastAPI
from .background import BackgroundTasks as BackgroundTasks
from .datastructures import UploadFile as UploadFile
from .exceptions import HTTPException as HTTPException
from .exceptions import WebSocketException as WebSocketException
from .param_functions import Body as Body

from fastapi import BackgroundTasks, FastAPI

app = FastAPI()


def write_notification(email: str, message=""):
    with open("log.txt", mode="w") as email_file:
        content = f"notification for {email}: {message}"
        email_file.write(content)


@app.post("/send-notification/{email}")
async def send_notification(email: str, background_tasks: BackgroundTasks):

import json

import pytest
from fastapi import BackgroundTasks, Depends, FastAPI
from fastapi.responses import StreamingResponse
from fastapi.testclient import TestClient

app = FastAPI()
state = {
    "/async": "asyncgen not started",
    "/sync": "generator not started",
    "/async_raise": "asyncgen raise not started",
    "/sync_raise": "generator raise not started",
    "context_a": "not started a",
    "context_b": "not started b",