```Python
with open("file.txt") as file:
    file.read()
```

⏮️ ⏬ 🐍, 📤 **🔁 🔑 👨‍💼**. 👆 🔜 ⚙️ ⚫️ ⏮️ `async with`:

```Python
async with lifespan(app):
    await do_stuff()
```

🕐❔ 👆 ✍ 🔑 👨‍💼 ⚖️ 🔁 🔑 👨‍💼 💖 🔛, ⚫️❔ ⚫️ 🔨 👈, ⏭ 🛬 `with` 🍫, ⚫️ 🔜 🛠️ 📟 ⏭ `yield`, & ⏮️ ❎ `with` 🍫, ⚫️ 🔜 🛠️ 📟 ⏮️ `yield`.

👆 📟 🖼 🔛, 👥 🚫 ⚙️ ⚫️ 🔗, ✋️ 👥 🚶‍♀️ ⚫️ FastAPI ⚫️ ⚙️ ⚫️.

        "requestBody": {
            "content": {"application/x-yaml": {"schema": Item.model_json_schema()}},
            "required": True,
        },
    },
)
async def create_item(request: Request):
    raw_body = await request.body()
    try:
        data = yaml.safe_load(raw_body)
    except yaml.YAMLError:
        raise HTTPException(status_code=422, detail="Invalid YAML")
    try:
        item = Item.model_validate(data)

      // SequentialExecutor by the time the barrier is satisfied
      barrier.await(1, SECONDS);
      executor.execute(barrierTask);
      // timeout means the second task wasn't even tried
      barrier.await(1, SECONDS);
    } finally {
      service.shutdown();
    }
  }

  public void testRejectedExecutionThrownWithMultipleCalls() throws Exception {

            })
        .start();

    // wait for the computingEntry to be created
    computationStarted.await();
    cache.invalidateAll();
    // let the computation proceed
    computingLatch.countDown();
    // don't check cache.size() until we know the get("b") call is complete
    computationComplete.await();

    // At this point, the listener should be holding the seed value (a -> a), and the map should

    legacy_request_state_context_var.reset(contextvar_token)


@app.middleware("http")
async def custom_middleware(
    request: Request, call_next: Callable[[Request], Awaitable[Response]]
):
    response = await call_next(request)
    response.headers["custom"] = "foo"
    return response


@app.get("/user", dependencies=[Depends(set_up_request_state_dependency)])
def get_user():

        .build()
    }
    val request =
      Request.Builder()
        .url(server.url("/"))
        .build()
    client.newCall(request).enqueue(callback)
    callback.await(request.url)
      .assertCode(200)
      .assertHeader("OkHttp-Intercepted", "yep")
  }

  @Test
  fun applicationInterceptorsCanMakeMultipleRequestsToServer() {

narrow, to be sure; but I THINK I can kick a little!'

  She drew her foot as far down the chimney as she could, and
waited till she heard a little animal (she couldn't guess of what
sort it was) scratching and scrambling about in the chimney close
above her:  then, saying to herself `This is Bill,' she gave one
sharp kick, and waited to see what would happen next.

  The first thing she heard was a general chorus of `There goes

		t.Fatalf("Output didn't match for '%s %s'\n got %v\nwant: %v", cmd.Name(), strings.Join(c.args, " "), output, c.expectedString)
	}

	if c.wantException {
		if fErr == nil {
			t.Fatalf("Wanted an exception for 'istioctl %s', didn't get one, output was %q",
				strings.Join(c.args, " "), output)
		}
	} else {
		if fErr != nil {

```

/// note | "技术细节"

您也可以使用 `from starlette.websockets import WebSocket`。

**FastAPI** 直接提供了相同的 `WebSocket`，只是为了方便开发人员。但它直接来自 Starlette。

///

## 等待消息并发送消息

在您的 WebSocket 路由中，您可以使用 `await` 等待消息并发送消息。

```Python hl_lines="48-52"
{!../../docs_src/websockets/tutorial001.py!}
```

您可以接收和发送二进制、文本和 JSON 数据。

## 尝试一下

如果您的文件名为 `main.py`，请使用以下命令运行应用程序：

```console

	dynamicTimeoutLogSize              = 16
	maxDuration                        = math.MaxInt64
	maxDynamicTimeout                  = 24 * time.Hour // Never set timeout bigger than this.
)

// timeouts that are dynamically adapted based on actual usage results
type dynamicTimeout struct {
	timeout       int64
	minimum       int64
	entries       int64
	log           [dynamicTimeoutLogSize]time.Duration
	mutex         sync.Mutex