# 并发 async / await

有关路径操作函数的 `async def` 语法以及异步代码、并发和并行的一些背景知识。

## 赶时间吗？

<abbr title="too long; didn't read(长文警告)"><strong>TL;DR:</strong></abbr>

如果你正在使用第三方库，它们会告诉你使用 `await` 关键字来调用它们，就像这样：

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

然后，通过 `async def` 声明你的 *路径操作函数*：

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

/// note

    - [Container Images](#container-images-15)
  - [Changelog since v1.27.0](#changelog-since-v1270)
  - [Urgent Upgrade Notes](#urgent-upgrade-notes)
    - [(No, really, you MUST read this before you upgrade)](#no-really-you-must-read-this-before-you-upgrade)
  - [Changes by Kind](#changes-by-kind-15)
    - [Deprecation](#deprecation)
    - [API Change](#api-change-4)
    - [Feature](#feature-12)

	c = append(c, gccMachine()...)
	if goos == "aix" {
		c = append(c, "-maix64")
		c = append(c, "-mcmodel=large")
	}
	// disable LTO so we get an object whose symbols we can read
	c = append(c, "-fno-lto")
	c = append(c, "-") //read input from standard input
	return c
}

// gccDebug runs gcc -gdwarf-2 over the C program stdin and
// returns the corresponding DWARF data and, if present, debug data block.

			return nil
		}
		return err
	}
	if len(data) == 0 {
		// Seems to be empty create a new poolMeta object.
		return nil
	}
	if len(data) <= 4 {
		return fmt.Errorf("poolMeta: no data")
	}
	// Read header
	switch binary.LittleEndian.Uint16(data[0:2]) {
	case poolMetaFormat:
	default:
		return fmt.Errorf("poolMeta: unknown format: %d", binary.LittleEndian.Uint16(data[0:2]))
	}

   * @since 31.0
   */
  @SafeVarargs
  public static <K, V> ImmutableMap<K, V> ofEntries(Entry<? extends K, ? extends V>... entries) {
    @SuppressWarnings("unchecked") // we will only ever read these
    Entry<K, V>[] entries2 = (Entry<K, V>[]) entries;
    return copyOf(Arrays.asList(entries2));
  }

  /**
   * Verifies that {@code key} and {@code value} are non-null, and returns a new immutable entry

   * @since 31.0
   */
  @SafeVarargs
  public static <K, V> ImmutableMap<K, V> ofEntries(Entry<? extends K, ? extends V>... entries) {
    @SuppressWarnings("unchecked") // we will only ever read these
    Entry<K, V>[] entries2 = (Entry<K, V>[]) entries;
    return RegularImmutableMap.fromEntries(entries2);
  }

  /**

    whole or in part contains or is derived from the Program or any part
    thereof, to be licensed as a whole at no charge to all third parties
    under the terms of this License.

    c) If the modified program normally reads commands interactively
    when run, you must cause it, when started running for such
    interactive use in the most ordinary way, to print or display an
    announcement including an appropriate copyright notice and a notice

            <![CDATA[
            The source control management system URL
            that describes the repository and how to connect to the
            repository.
            This connection is read-only.
            <br><b>Default value is</b>: parent value [+ path adjustment] + (artifactId or project.directory property), or just parent value if
            scm's {@code child.scm.connection.inherit.append.path="false"}

    /** The key of the message: Failed to start reindexing from {0} to {1} */
    public static final String ERRORS_failed_to_reindex = "{errors.failed_to_reindex}";

    /** The key of the message: Failed to read request file: {0} */
    public static final String ERRORS_failed_to_read_request_file = "{errors.failed_to_read_request_file}";

    /** The key of the message: Invalid header: {0} */

		// Fan-out requires no copying, and must be carried from original source
		// https://en.wikipedia.org/wiki/Copy_protection so the incoming stream
		// is always going to be in-memory as we cannot re-read from what we
		// wrote to disk - since that amounts to "copying" from a "copy"
		// instead of "copying" from source, we need the stream to be seekable
		// to ensure that we can make fan-out calls concurrently.