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docs/zh-hant/docs/tutorial/background-tasks.md

**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。

它可以是 `async def`，也可以是一般的 `def`，**FastAPI** 都能正確處理。

在此例中，任務函式會寫入檔案（模擬寄送電子郵件）。

由於寫入操作未使用 `async` 與 `await`，因此以一般的 `def` 定義該函式：

{* ../../docs_src/background_tasks/tutorial001_py310.py hl[6:9] *}

## 新增背景任務 { #add-the-background-task }

在路徑操作函式內，使用 `.add_task()` 將任務函式加入背景任務物件：

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github.com/tiangolo/fastapi

docs_src/custom_response/tutorial010_py310.py

from fastapi import FastAPI
from fastapi.responses import HTMLResponse

app = FastAPI(default_response_class=HTMLResponse)


@app.get("/items/")
async def read_items():

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

docs_src/debugging/tutorial001_py310.py

import uvicorn
from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def root():
    a = "a"
    b = "b" + a
    return {"hello world": b}


if __name__ == "__main__":

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github.com/tiangolo/fastapi

tests/test_router_circular_import.py

import pytest
from fastapi import APIRouter


def test_router_circular_import():
    router = APIRouter()

    with pytest.raises(
        AssertionError,
        match="Cannot include the same APIRouter instance into itself. Did you mean to include a different router?",
    ):

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

docs_src/query_params/tutorial006_py310.py

from fastapi import FastAPI

app = FastAPI()


@app.get("/items/{item_id}")
async def read_user_item(
    item_id: str, needy: str, skip: int = 0, limit: int | None = None
):
    item = {"item_id": item_id, "needy": needy, "skip": skip, "limit": limit}

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

docs_src/custom_response/tutorial002_py310.py

from fastapi import FastAPI
from fastapi.responses import HTMLResponse

app = FastAPI()


@app.get("/items/", response_class=HTMLResponse)
async def read_items():
    return """
    <html>
        <head>
            <title>Some HTML in here</title>
        </head>
        <body>
            <h1>Look ma! HTML!</h1>
        </body>
    </html>

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

docs_src/response_model/tutorial003_01_py310.py

app = FastAPI()


class BaseUser(BaseModel):
    username: str
    email: EmailStr
    full_name: str | None = None


class UserIn(BaseUser):
    password: str


@app.post("/user/")
async def create_user(user: UserIn) -> BaseUser:

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/apache/maven

impl/maven-cli/src/main/java/org/apache/maven/cling/invoker/logging/SystemLogger.java

        this.threshold = Objects.requireNonNullElse(threshold, Level.INFO);
    }

    private PrintStream toPsOrDef(OutputStream outputStream, PrintStream def) {
        if (outputStream == null) {
            return def;
        }
        if (outputStream instanceof PrintStream ps) {
            return ps;
        }
        return new PrintStream(outputStream, true);
    }

    @Override

Created: Sun Apr 05 03:35:12 GMT 2026

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github.com/tiangolo/fastapi

docs_src/settings/tutorial001_py310.py


class Settings(BaseSettings):
    app_name: str = "Awesome API"
    admin_email: str
    items_per_user: int = 50


settings = Settings()
app = FastAPI()


@app.get("/info")
async def info():
    return {
        "app_name": settings.app_name,
        "admin_email": settings.admin_email,
        "items_per_user": settings.items_per_user,

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

docs_src/response_model/tutorial002_py310.py

app = FastAPI()


class UserIn(BaseModel):
    username: str
    password: str
    email: EmailStr
    full_name: str | None = None


# Don't do this in production!
@app.post("/user/")
async def create_user(user: UserIn) -> UserIn:

Created: Sun Apr 05 07:19:11 GMT 2026

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