## 情境管理器 { #context-managers }

### 什麼是「情境管理器」 { #what-are-context-managers }

「情境管理器」是那些你可以在 `with` 陳述式中使用的 Python 物件。

例如，[你可以用 `with` 來讀取檔案](https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files)：

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```

在底層，`open("./somefile.txt")` 會建立一個稱為「情境管理器」的物件。

"Gerenciadores de Contexto" são qualquer um dos objetos Python que podem ser utilizados com a declaração `with`.

Por exemplo, [você pode utilizar `with` para ler um arquivo](https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files):

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```

{* ../../docs_src/settings/app02_an_py310/test_main.py hl[9:10,13,21] *}

在依赖项覆盖中，我们在创建新的 `Settings` 对象时为 `admin_email` 设置了一个新值，然后返回该新对象。

然后我们可以测试它是否被使用。

## 读取 `.env` 文件 { #reading-a-env-file }

如果你有许多设置可能经常变化，或在不同环境中不同，那么把它们放进一个文件中，然后像环境变量一样从中读取，可能非常有用。

这种做法非常常见：这些环境变量通常放在名为 `.env` 的文件中，该文件被称为 “dotenv”。

/// tip | 提示

以点（`.`）开头的文件在类 Unix 系统（如 Linux 和 macOS）中是隐藏文件。

// Discard skips the next n bytes, returning the number of bytes discarded.
//
// If Discard skips fewer than n bytes, it also returns an error.
// If 0 <= n <= b.Buffered(), Discard is guaranteed to succeed without
// reading from the underlying io.Reader.
func (b *Reader) Discard(n int) (discarded int, err error) {
	if n < 0 {
		return 0, ErrNegativeCount
	}
	if n == 0 {
		return
	}

	b.lastByte = -1

    protected int handleReconnectRetries = 3;
    /** Directory to store persistent handle state */
    protected String handleStateDirectory;

    // Directory leasing configuration fields
    /**
     * Whether to use directory leasing for cached directory listings
     */
    protected boolean useDirectoryLeasing = true;
    /**

	ReplicateIncomingDelete = "replicate:incoming:delete"

	// ReplicateHeal - audit trail for healing of failed/pending replications
	ReplicateHeal = "replicate:heal"
	// ReplicateHealDelete - audit trail of healing of failed/pending delete replications.
	ReplicateHealDelete = "replicate:heal:delete"
)

var (
	globalReplicationPool  = once.NewSingleton[ReplicationPool]()

   * body. This was misleading for tracing because it was too early.
   */
  open fun responseBodyStart(call: Call) {
  }

  /**
   * Invoked immediately after receiving a response body and completing reading it.
   *
   * Will only be invoked for requests having a response body e.g. won't be invoked for a web socket
   * upgrade.
   *

		}
	}

	contentBytes, err := io.ReadAll(resp.Body)
	if err != nil {
		return content, AdminError{
			Code:       AdminUpdateUnexpectedFailure,
			Message:    fmt.Sprintf("Error reading response. %s", err),
			StatusCode: http.StatusInternalServerError,
		}
	}

	return string(contentBytes), nil
}

func releaseInfoToReleaseTime(releaseInfo string) (releaseTime time.Time, err error) {

«Контекстные менеджеры» — это любые объекты Python, которые можно использовать в операторе `with`.

Например, [можно использовать `with` для чтения файла](https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files):

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```

        // Since it costs IO to compute this, and is done at configuration time we want to cache this if possible
        // It's safe to store this in a static variable since it's just a primitive so leaking memory isn't an issue
        if (_defaultParallel == null) {
            File cpuInfoFile = new File("/proc/cpuinfo");
            if (cpuInfoFile.exists()) {