# Concorrência e async / await

Detalhes sobre a sintaxe `async def` para *funções de operação de rota* e alguns conceitos de código assíncrono, concorrência e paralelismo.

## Com pressa?

<abbr title="muito longo; não li"><strong>TL;DR:</strong></abbr>

Se você estiver utilizando bibliotecas de terceiros que dizem para você chamar as funções com `await`, como:

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

    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

          fail("")
        }
      },
    )
    assertThat(server.takeRequest().sequenceNumber)
      .isEqualTo(expectedSequenceNumber)
    responseDequeuedLatch!!.await()
    call.cancel()
    requestCanceledLatch!!.countDown()
    latch.await()
  }

  @ParameterizedTest
  @ArgumentsSource(ProtocolParamProvider::class)
  fun noRecoveryFromRefusedStreamWithRetryDisabled(
    protocol: Protocol,

🚥 👆 ⚙️ 🥉 🥳 🗃 👈 💬 👆 🤙 👫 ⏮️ `await`, 💖:

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

⤴️, 📣 👆 *➡ 🛠️ 🔢* ⏮️ `async def` 💖:

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

/// note

👆 💪 🕴 ⚙️ `await` 🔘 🔢 ✍ ⏮️ `async def`.

///

---

	})
	return err
}

// PipeReader is similar to io.PipeReader with wait group
type PipeReader struct {
	*io.PipeReader
	wait func()
}

// CloseWithError close with supplied error the reader end
func (r *PipeReader) CloseWithError(err error) error {
	err = r.PipeReader.CloseWithError(err)
	r.wait()
	return err
}

// WaitPipe implements wait-group backend io.Pipe to provide

# Nebenläufigkeit und async / await

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

## In Eile?

<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
results = await some_library()
```

          t: Throwable,
          response: Response?,
        ) {
          t.printStackTrace(System.out)
          latch.countDown()
        }
      },
    )

    check(latch.await(30, TimeUnit.SECONDS)) { "Timed out waiting for test $number to finish." }
    val endNanos = System.nanoTime()
    val tookMs = TimeUnit.NANOSECONDS.toMillis(endNanos - startNanos.get())
    println("Took ${tookMs}ms")
  }

</html>
"""


@app.get("/")
async def get():
    return HTMLResponse(html)


@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    await websocket.accept()
    while True:
        data = await websocket.receive_text()

    exit_limiter = CapacityLimiter(1)
    try:
        yield await run_in_threadpool(cm.__enter__)
    except Exception as e:
        ok = bool(
            await anyio.to_thread.run_sync(
                cm.__exit__, type(e), e, None, limiter=exit_limiter
            )
        )
        if not ok:
            raise e
    else:
        await anyio.to_thread.run_sync(

    }
  }

  /**
   * Like [Object.wait], but throws an [InterruptedIOException] when interrupted instead of the more
   * awkward [InterruptedException].
   */
  @Throws(InterruptedIOException::class)
  internal fun waitForIo() {
    try {
      condition.await()
    } catch (_: InterruptedException) {