# 동시성과 async / await

*경로 작동 함수*에서의 `async def` 문법에 대한 세부사항과 비동기 코드, 동시성 및 병렬성에 대한 배경

## 바쁘신 경우

<strong>요약</strong>

다음과 같이 `await`를 사용해 호출하는 제3의 라이브러리를 사용하는 경우:

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

다음처럼 *경로 작동 함수*를 `async def`를 사용해 선언하십시오:

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

/// note | 참고

* `seek(offset)`: Goes to the byte position `offset` (`int`) in the file.
    * E.g., `await myfile.seek(0)` would go to the start of the file.
    * This is especially useful if you run `await myfile.read()` once and then need to read the contents again.
* `close()`: Closes the file.

As all these methods are `async` methods, you need to "await" them.

For example, inside of an `async` *path operation function* you can get the contents with:

          @Override
          protected void finalize() {
            latch.countDown();
          }
        };
    unused = null; // Hint to the JIT that unused is unreachable
    GcFinalization.await(latch);
    assertEquals(0, latch.getCount());
  }

  public void testAwaitDone_future() {
    SettableFuture<@Nullable Void> future = SettableFuture.create();
    Object unused =
        new Object() {

请注意，测试函数现在用的是 `async def`，而不是像以前使用 `TestClient` 时那样只是 `def` 。

///

我们现在可以使用应用程序创建一个 `AsyncClient` ，并使用 `await` 向其发送异步请求。

{* ../../docs_src/async_tests/test_main.py hl[9:12] *}

这相当于：

```Python
response = client.get('/')
```

我们曾经通过它向 `TestClient` 发出请求。

/// tip

请注意，我们正在将 async/await 与新的 `AsyncClient` 一起使用——请求是异步的。

///

/// warning

 * Object x = new MyClass() {
 *   ...
 *   protected void finalize() { latch.countDown(); ... }
 * };
 * x = null;  // Hint to the JIT that x is stack-unreachable
 * GcFinalization.await(latch);
 * }
 *
 * <p>Here's an example that uses a user-defined finalization predicate:
 *
 * {@snippet :
 * final WeakHashMap<Object, Object> map = new WeakHashMap<>();
 * map.put(new Object(), Boolean.TRUE);

    callback.await(server.url("/a")).assertBody("abc")
    client.newCall(Request.Builder().url(server.url("/b")).build()).enqueue(callback)
    callback.await(server.url("/b")).assertBody("def")
    client.newCall(Request.Builder().url(server.url("/c")).build()).enqueue(callback)
    callback.await(server.url("/c")).assertBody("ghi")

    /**
     * Constructs a pipe wait request without timeout.
     *
     * @param name the pipe name to wait for
     */
    public FsctlPipeWaitRequest(final String name) {
        this.nameBytes = name.getBytes(StandardCharsets.UTF_16LE);
        this.timeoutSpecified = false;
        this.timeout = 0;
    }

    /**
     * Constructs a pipe wait request with timeout.
     *

**FastAPI** provides the same `WebSocket` directly just as a convenience for you, the developer. But it comes directly from Starlette.

///

## Await for messages and send messages { #await-for-messages-and-send-messages }

In your WebSocket route you can `await` for messages and send messages.

{* ../../docs_src/websockets/tutorial001.py hl[48:52] *}

You can receive and send binary, text, and JSON data.

    * E.g., `await myfile.seek(0)` navegaria para o ínicio do arquivo.
    * Isso é especialmente útil se você executar `await myfile.read()` uma vez e depois precisar ler os conteúdos do arquivo de novo.
* `close()`: Fecha o arquivo.

Como todos esses métodos são assíncronos (`async`) você precisa esperar ("await") por eles.

* `seek(versatz)`: Geht zur Position `versatz` (`int`) in der Datei.
    * Z. B. würde `await myfile.seek(0)` zum Anfang der Datei gehen.
    * Das ist besonders dann nützlich, wenn Sie `await myfile.read()` einmal ausführen und dann diese Inhalte erneut auslesen müssen.
* `close()`: Schließt die Datei.

Da alle diese Methoden `async`hron sind, müssen Sie sie `await`en („erwarten“).