```Python hl_lines="2"
@app.get('/')
def results():
    results = some_library()
    return results
```

---

If your application (somehow) doesn't have to communicate with anything else and wait for it to respond, use `async def`.

---

If you just don't know, use normal `def`.

---

```Python hl_lines="2"
@app.get('/')
def results():
    results = some_library()
    return results
```

---

만약 당신의 응용프로그램이 (어째서인지) 다른 무엇과 의사소통하고 그것이 응답하기를 기다릴 필요가 없다면 `async def`를 사용하십시오.

---

모르겠다면, 그냥 `def`를 사용하십시오.

---

## HTTPX

Even if your **FastAPI** application uses normal `def` functions instead of `async def`, it is still an `async` application underneath.

```

### About `def` vs `async def`

The same as with SQLAlchemy, we are not doing something like:

```Python
user = await models.User.select().first()
```

...but instead we are using:

```Python
user = models.User.select().first()
```

So, again, we should declare the *path operation functions* and the dependency without `async def`, just with a normal `def`, as:

   FDD0-FDEF; [NONCHARACTER CODE POINTS]
   FFFE-FFFF; [NONCHARACTER CODE POINTS]
   1FFFE-1FFFF; [NONCHARACTER CODE POINTS]
   2FFFE-2FFFF; [NONCHARACTER CODE POINTS]
   3FFFE-3FFFF; [NONCHARACTER CODE POINTS]
   4FFFE-4FFFF; [NONCHARACTER CODE POINTS]
   5FFFE-5FFFF; [NONCHARACTER CODE POINTS]
   6FFFE-6FFFF; [NONCHARACTER CODE POINTS]
   7FFFE-7FFFF; [NONCHARACTER CODE POINTS]
   8FFFE-8FFFF; [NONCHARACTER CODE POINTS]

  }

  @AfterEach
  fun tearDown() {
    socksProxy.shutdown()
  }

  @Test
  fun proxy() {
    server.enqueue(MockResponse.Builder().body("abc").build())
    server.enqueue(MockResponse.Builder().body("def").build())
    val client =
      clientTestRule.newClientBuilder()
        .proxy(socksProxy.proxy())
        .build()
    val request1 = Request.Builder().url(server.url("/")).build()

    assertThat(response1.body.source().readUtf8(3)).isEqualTo("ABC")
    assertThat(response2.body.source().readUtf8(3)).isEqualTo("GHI")
    assertThat(response1.body.source().readUtf8(3)).isEqualTo("DEF")
    assertThat(response2.body.source().readUtf8(3)).isEqualTo("JKL")
    assertThat(server.takeRequest().sequenceNumber).isEqualTo(0)
    assertThat(server.takeRequest().sequenceNumber).isEqualTo(1)
    response1.close()

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>Ya da <code>async def</code>...</summary>

Eğer kodunuzda `async` / `await` varsa, `async def` kullanalım:

```Python hl_lines="9  14"

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>Або використайте <code>async def</code>...</summary>

Якщо ваш код використовує `async` / `await`, скористайтеся `async def`:

```Python hl_lines="9  14"

```

**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

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。

它可以是 `async def` 或普通的 `def` 函数，**FastAPI** 知道如何正确处理。

在这种情况下，任务函数将写入一个文件（模拟发送电子邮件）。

由于写操作不使用 `async` 和 `await`，我们用普通的 `def` 定义函数：

```Python hl_lines="6-9"
{!../../../docs_src/background_tasks/tutorial001.py!}
```

## 添加后台任务