```Python
burgers = await get_burgers(2)
```

The key here is the `await`. It tells Python that it has to wait ⏸ for `get_burgers(2)` to finish doing its thing 🕙 before storing the results in `burgers`. With that, Python will know that it can go and do something else 🔀 ⏯ in the meanwhile (like receiving another request).

      thread.start();
      // we want to wait until each thread is WAITING - one thread waiting inside CacheLoader.load
      // (in startSignal.await()), and the others waiting for that thread's result.
      while (thread.isAlive() && thread.getState() != Thread.State.WAITING) {
        Thread.yield();
      }
    }
    gettersStartedSignal.countDown();
    gettersComplete.await();

app = FastAPI()


@app.get("/")
async def read_main():
    return {"msg": "Hello World"}


@app.websocket("/ws")
async def websocket(websocket: WebSocket):
    await websocket.accept()
    await websocket.send_json({"msg": "Hello WebSocket"})
    await websocket.close()


def test_read_main():
    client = TestClient(app)
    response = client.get("/")
    assert response.status_code == 200

              }
            })
        .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();

                functionBlocking.await();
                return immediateFuture(null);
              }
            });

    ExecutorService executor = Executors.newSingleThreadExecutor();
    try {
      ListenableFuture<?> output =
          Futures.transformAsync(immediateFuture(null), function, executor);
      functionCalled.await();
      assertThat(output.toString()).contains(function.toString());

# Concurrencia y async / await

Detalles sobre la sintaxis `async def` para *path operation functions* y un poco de información sobre código asíncrono, concurrencia y paralelismo.

## ¿Tienes prisa?

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

Si estás utilizando libraries de terceros que te dicen que las llames con `await`, del tipo:

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

                }
            }, "ProcessCloser-output-" + sessionId).start();

            try {
                latch.await(10, TimeUnit.SECONDS);
            } catch (final InterruptedException e) {
                logger.warn("Interrupted to wait a process.", e);
            }
            try {
                process.destroyForcibly().waitFor(processDestroyTimeout, TimeUnit.SECONDS);

    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(

    assertFalse(service.startUpCalled);

    service.startAsync().awaitRunning();
    assertTrue(service.startUpCalled);
    assertEquals(Service.State.RUNNING, service.state());

    enterRun.await(); // to avoid stopping the service until run() is invoked

    service.stopAsync().awaitTerminated();
    assertTrue(service.shutDownCalled);
    assertEquals(Service.State.TERMINATED, service.state());

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

In recent versions of Python, there's also an **async context manager**. You would use it with `async with`:

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