Pour y parvenir, vous aurez normalement un **programme séparé** qui s'assure que votre application est lancée au démarrage. Et dans de nombreux cas, il s'assurera également que d'autres composants ou applications sont également lancés, par exemple une base de données.

### Exemples d’outils pour lancer au démarrage { #example-tools-to-run-at-startup }

Voici quelques exemples d'outils capables de faire ce travail :

{* ../../docs_src/handling_errors/tutorial001_py310.py hl[1] *}

### Lance o `HTTPException` no seu código { #raise-an-httpexception-in-your-code }

`HTTPException`, ao fundo, nada mais é do que a conjunção entre uma exceção comum do Python e informações adicionais relevantes para APIs.

E porque é uma exceção do Python, você não **retorna** (return) o `HTTPException`, você lança o (raise) no seu código.

    assertFailed(future, cause);
  }

  public void testCanceled() throws Exception {
    assertThat(future.cancel(false /* mayInterruptIfRunning */)).isTrue();
    assertCancelled(future, false);
  }

  public void testInterrupted() throws Exception {
    assertThat(future.cancel(true /* mayInterruptIfRunning */)).isTrue();
    assertCancelled(future, true);
  }

    inputFuture.cancel(true); // argument is ignored
    assertThrows(CancellationException.class, () -> resultFuture.get());
  }

  public void testFutureGetThrowsCancellationIfOutputCancelled() throws Exception {
    inputFuture.set(SLOW_OUTPUT_VALID_INPUT_DATA);
    outputFuture.cancel(true); // argument is ignored

    inputFuture.cancel(true); // argument is ignored
    assertThrows(CancellationException.class, () -> resultFuture.get());
  }

  public void testFutureGetThrowsCancellationIfOutputCancelled() throws Exception {
    inputFuture.set(SLOW_OUTPUT_VALID_INPUT_DATA);
    outputFuture.cancel(true); // argument is ignored

    assertFailed(future, cause);
  }

  public void testCanceled() throws Exception {
    assertThat(future.cancel(false /* mayInterruptIfRunning */)).isTrue();
    assertCancelled(future, false);
  }

  public void testInterrupted() throws Exception {
    assertThat(future.cancel(true /* mayInterruptIfRunning */)).isTrue();
    assertCancelled(future, true);
  }

    async.setFuture(inner);
    async.cancel(false);
    assertTrue(inner.isCancelled());
    assertFalse(inner.wasInterrupted());
    assertThrows(CancellationException.class, inner::get);
  }

  public void testCancel_beforeSet() throws Exception {
    SettableFuture<Object> async = SettableFuture.create();
    async.cancel(true);
    assertFalse(async.set(42));
  }

    async.setFuture(inner);
    async.cancel(false);
    assertTrue(inner.isCancelled());
    assertFalse(inner.wasInterrupted());
    assertThrows(CancellationException.class, inner::get);
  }

  public void testCancel_beforeSet() throws Exception {
    SettableFuture<Object> async = SettableFuture.create();
    async.cancel(true);
    assertFalse(async.set(42));
  }

    // stop it.
    blockingCallable.waitForStart();

    // This time, cancel the future for the first task. The task remains running, only the future
    // is cancelled.
    future1.cancel(false);

    // Give the second task a chance to (incorrectly) start up while the first task is running.
    // (This is the assertion that fails.)

    inFinished: Boolean,
  ) {
    pushQueue.execute("$connectionName[$streamId] onHeaders") {
      val cancel = pushObserver.onHeaders(streamId, requestHeaders, inFinished)
      ignoreIoExceptions {
        if (cancel) writer.rstStream(streamId, ErrorCode.CANCEL)
        if (cancel || inFinished) {
          withLock {
            currentPushRequests.remove(streamId)
          }
        }
      }