):
    await websocket.accept()
    while True:
        data = await websocket.receive_text()
        await websocket.send_text(
            f"Session cookie or query token value is: {cookie_or_token}"
        )
        if q is not None:
            await websocket.send_text(f"Query parameter q is: {q}")

* `read(size)`：按指定数量的字节或字符（`size` (`int`)）读取文件内容；
* `seek(offset)`：移动至文件 `offset` （`int`）字节处的位置；
    * 例如，`await myfile.seek(0) ` 移动到文件开头；
    * 执行 `await myfile.read()` 后，需再次读取已读取内容时，这种方法特别好用；
* `close()`：关闭文件。

因为上述方法都是 `async` 方法，要搭配「await」使用。

例如，在 `async` *路径操作函数* 内，要用以下方式读取文件内容：

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

在普通 `def` *路径操作函数*  内，则可以直接访问 `UploadFile.file`，例如：

```Python

	<script src="../../lib/wasm/wasm_exec.js"></script>
	<script>
		if (!WebAssembly.instantiateStreaming) { // polyfill
			WebAssembly.instantiateStreaming = async (resp, importObject) => {
				const source = await (await resp).arrayBuffer();
				return await WebAssembly.instantiate(source, importObject);
			};
		}

		const go = new Go();
		let mod, inst;
		WebAssembly.instantiateStreaming(fetch("test.wasm"), go.importObject).then((result) => {

# Concurrencia y async / await { #concurrency-and-async-await }

Detalles sobre la sintaxis `async def` para *path operation functions* y algunos antecedentes sobre el código asíncrono, la concurrencia y el paralelismo.

## ¿Con prisa? { #in-a-hurry }

<abbr title="too long; didn't read"><strong>TL;DR:</strong></abbr>

Si estás usando paquetes de terceros que te dicen que los llames con `await`, como:

```Python
results = await some_library()
```

@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket, session: SessionDep):
    await websocket.accept()
    for item in session:
        await websocket.send_text(f"{item}")


@app.websocket("/ws-broken")
async def websocket_endpoint_broken(websocket: WebSocket, session: BrokenSessionDep):
    await websocket.accept()
    for item in session:
        await websocket.send_text(f"{item}")  # pragma no cover


client = TestClient(app)

Подробности о синтаксисе `async def` для *функций-обработчиков пути* и немного фона об асинхронном коде, конкурентности и параллелизме.

## Нет времени? { #in-a-hurry }

<abbr title="too long; didn't read – слишком длинно; не читал"><strong>TL;DR:</strong></abbr>

Если вы используете сторонние библиотеки, которые нужно вызывать с `await`, например:

```Python
results = await some_library()
```

# Nebenläufigkeit und async / await { #concurrency-and-async-await }

Details zur `async def`-Syntax für *Pfadoperation-Funktionen* und Hintergrundinformationen zu asynchronem Code, Nebenläufigkeit und Parallelität.

## In Eile? { #in-a-hurry }

<abbr title="too long; didn't read – Zu lang; nicht gelesen"><strong>TL;DR:</strong></abbr>

Wenn Sie Bibliotheken von Dritten verwenden, die mit `await` aufgerufen werden müssen, wie zum Beispiel:

```Python

    await websocket.accept()  # pragma: no cover
    await websocket.send_text(f"Item: {item_id}")  # pragma: no cover
    await websocket.close()  # pragma: no cover


@sub_app.websocket("/ws/{item_id}")
async def subapp_websocket_endpoint(websocket: WebSocket, item_id: int):
    await websocket.accept()  # pragma: no cover
    await websocket.send_text(f"Item: {item_id}")  # pragma: no cover

    cookie_or_token: str = Depends(get_cookie_or_token),
):
    await websocket.accept()
    while True:
        data = await websocket.receive_text()
        await websocket.send_text(
            f"Session cookie or query token value is: {cookie_or_token}"
        )
        if q is not None:
            await websocket.send_text(f"Query parameter q is: {q}")

    return value


@app.websocket("/ws")
async def get_value_by_ws(
    websocket: WebSocket, value: int = Depends(extract_value_from_http_connection)
):
    await websocket.accept()
    await websocket.send_json(value)
    await websocket.close()


client = TestClient(app)


def test_value_extracting_by_http():
    response = client.get("/http")
    assert response.status_code == 200