### Dateien und Async { #files-and-async }

In den meisten Fällen sind dateiähnliche Objekte standardmäßig nicht mit async und await kompatibel.

Beispielsweise haben sie kein `await file.read()` oder `async for chunk in file`.

Und in vielen Fällen wäre das Lesen eine blockierende Operation (die die Event-Loop blockieren könnte), weil von der Festplatte oder aus dem Netzwerk gelesen wird.

        "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)

import jcifs.Configuration;

/**
 * SMB1 Transaction Wait Named Pipe request implementation.
 * Implements the TRANS_WAIT_NAMED_PIPE transaction to wait for a named pipe
 * to become available when the pipe server is busy or temporarily unavailable.
 *
 * @author mbechler
 */
public class TransWaitNamedPipe extends SmbComTransaction {

    /**
     * Constructs a wait request for a named pipe.
     *

### Archivos y async { #files-and-async }

En la mayoría de los casos, los objetos tipo archivo no son compatibles con `async` y `await` por defecto.

Por ejemplo, no tienen un `await file.read()`, ni un `async for chunk in file`.

Y en muchos casos leerlos sería una operación bloqueante (que podría bloquear el event loop), porque se leen desde disco o desde la red.

* `seek(offset)`: 파일 내 `offset`(`int`) 위치의 바이트로 이동합니다.
    * 예) `await myfile.seek(0)` 를 사용하면 파일의 시작부분으로 이동합니다.
    * `await myfile.read()` 를 사용한 후 내용을 다시 읽을 때 유용합니다.
* `close()`: 파일을 닫습니다.

상기 모든 메소드들이 `async` 메소드이기 때문에 “await”을 사용하여야 합니다.

예를들어, `async` *경로 처리 함수*의 내부에서 다음과 같은 방식으로 내용을 가져올 수 있습니다:

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

Use `async` *path operations* only when fully certain that the logic called inside is compatible with async and await (it's called with `await`) or that doesn't block.

```python
from fastapi import FastAPI

app = FastAPI()


# Use async def when calling async code
@app.get("/async-items/")
async def read_async_items():
    data = await some_async_library.fetch_items()
    return data

        byte[] payload = new byte[] { 1, 2, 3, 4 };

        w.start();

        // Wait until writer thread signals readiness
        synchronized (w) {
            long deadline = System.currentTimeMillis() + 2000;
            while (!w.isReady() && System.currentTimeMillis() < deadline) {
                w.wait(10);
            }
            assertTrue(w.isReady(), "WriterThread should be ready to accept work");

### Dosyalar ve Async { #files-and-async }

Çoğu durumda dosya benzeri nesneler, varsayılan olarak async ve await ile uyumlu değildir.

Örneğin, `await file.read()` ya da `async for chunk in file` gibi şeyler yoktur.

Ve birçok durumda, diskte ya da ağda okundukları için, okumak engelleyici (event loop'u bloke edebilen) bir işlem olabilir.

/// info | Bilgi

     * as well as a groovy AntBuilder, to enable running ant condition checks. The default wait
     * condition is for http on the http port.
     */
    @Internal
    Closure waitCondition = { AntFixture fixture, AntBuilder ant ->
        File tmpFile = new File(fixture.cwd, 'wait.success')
        ant.get(src: "http://${fixture.addressAndPort}",
                dest: tmpFile.toString(),

采用异步生成器或普通生成器/迭代器（带有 `yield` 的函数），然后流式传输响应主体。

{* ../../docs_src/custom_response/tutorial007_py310.py hl[3,16] *}

/// note | 技术细节

一个 `async` 任务只有在到达 `await` 时才能被取消。如果没有 `await`，生成器（带有 `yield` 的函数）无法被正确取消，即使已请求取消也可能继续运行。

由于这个小示例不需要任何 `await` 语句，我们添加 `await anyio.sleep(0)`，给事件循环一个处理取消的机会。

对于大型或无限流，这一点更为重要。

///

/// tip | 提示

与其直接返回 `StreamingResponse`，更推荐遵循 [流式数据](./stream-data.md) 的写法，它更方便并在幕后为你处理取消。