非同期コードの操作がはるかに簡単になります。

等価な (またはほとんど同一の) 構文が、最近のバージョンのJavaScript (ブラウザおよびNodeJS) にも最近組み込まれました。

しかし、その前は、非同期コードの処理はかなり複雑で難解でした。

以前のバージョンのPythonでは、スレッドや<a href="https://www.gevent.org/" class="external-link" target="_blank">Gevent</a>が利用できました。しかし、コードは理解、デバック、そして、考察がはるかに複雑です。

以前のバージョンのNodeJS / ブラウザJavaScriptでは、「コールバック」を使用していました。これは、「コールバック地獄」につながります。

## コルーチン

👉 👗 ⚙️ `async` & `await` 📶 🆕 🇪🇸.

✋️ ⚫️ ⚒ 👷 ⏮️ 🔁 📟 📚 ⏩.

👉 🎏 ❕ (⚖️ 🌖 🌓) 🔌 ⏳ 🏛 ⏬ 🕸 (🖥 & ✳).

✋️ ⏭ 👈, 🚚 🔁 📟 🌖 🏗 & ⚠.

⏮️ ⏬ 🐍, 👆 💪 ✔️ ⚙️ 🧵 ⚖️ <a href="https://www.gevent.org/" class="external-link" target="_blank">🐁</a>. ✋️ 📟 🌌 🌖 🏗 🤔, ℹ, &amp; 💭 🔃.

⏮️ ⏬ ✳ / 🖥 🕸, 👆 🔜 ✔️ ⚙️ "⏲". ❔ ↘️ "⏲ 🔥😈".

## 🔁

        // Create different implementations
        SearchLogEvent event1 = new TestSearchLogEvent("id1", 1L, "type1");
        SearchLogEvent event2 = new NullSearchLogEvent();
        SearchLogEvent event3 = new EmptySearchLogEvent();

        // Test polymorphic behavior
        SearchLogEvent[] events = { event1, event2, event3 };

        for (SearchLogEvent event : events) {
            // All methods should be callable without exceptions

Diese Funktionen können mit `async def` oder normalem `def` deklariert werden.

### `startup`-Event

Um eine Funktion hinzuzufügen, die vor dem Start der Anwendung ausgeführt werden soll, deklarieren Sie diese mit dem Event `startup`:

{* ../../docs_src/events/tutorial001.py hl[8] *}

In this case, the `startup` event handler function will initialize the items "database" (just a `dict`) with some values.

You can add more than one event handler function.

And your application won't start receiving requests until all the `startup` event handlers have completed.

### `shutdown` event { #shutdown-event }

To add a function that should be run when the application is shutting down, declare it with the event `"shutdown"`:

	UserAgent    string
}

// ToEvent - converts to notification event.
func (args eventArgs) ToEvent(escape bool) event.Event {
	eventTime := UTCNow()
	uniqueID := fmt.Sprintf("%X", eventTime.UnixNano())
	if !args.Object.ModTime.IsZero() {
		uniqueID = fmt.Sprintf("%X", args.Object.ModTime.UnixNano())
	}

	respElements := map[string]string{
		"x-amz-request-id": args.RespElements["requestId"],

import org.apache.maven.api.annotations.Nonnull;

/**
 * Event sent by maven during various phases of the build process.
 * Such events can be listened to using {@link Listener}s objects
 * registered in the {@link Session}.
 *
 * @since 4.0.0
 */
@Experimental
public interface Event {

    /**
     * Gets the type of the event.
     *
     * @return the type of the event, never {@code null}
     */
    @Nonnull

![Events Diagram](../assets/images/events@2x.png)

Here’s a [sample event listener](https://github.com/square/okhttp/blob/master/samples/guide/src/main/java/okhttp3/recipes/PrintEventsNonConcurrent.java) that prints each event with a timestamp.

```java

        ErrorToWarnRewritePolicy policy = new ErrorToWarnRewritePolicy(loggerNames);

        LogEvent event =
                Log4jLogEvent.newBuilder().setLoggerName(null).setLevel(Level.ERROR).setMessage(new SimpleMessage("test message")).build();

        LogEvent result = policy.rewrite(event);
        assertSame(event, result);
    }

    public void test_rewrite_error_to_warn_matching_logger() {

E sua aplicação não irá começar a receber requisições até que todos os manipuladores de eventos de `startup` sejam concluídos.

### Evento `shutdown`

Para adicionar uma função que deve ser executada quando a aplicação estiver encerrando, declare ela com o evento `"shutdown"`:

{* ../../docs_src/events/tutorial002.py hl[6] *}