"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。

«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)
```

   * 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.
   *

        try {
            context.extensions = readCoreExtensionsDescriptor(context);
        } catch (Exception e) {
            context.parsingFailed = true;
            parserRequest.logger().error("Error reading core extensions descriptor", e);
        }

        // CI detection
        context.ciInfo = detectCI(context);

        // only if not failed so far; otherwise we may have no options to validate

		// Buffer size greater than object size. - 6
		{
			volume, "myobject", 0, 16,
			[]byte("hello, world"),
			io.ErrUnexpectedEOF,
		},
		// Reading from an offset success. - 7
		{
			volume, "myobject", 7, 5,
			[]byte("world"), nil,
		},
		// Reading from an object but buffer size greater. - 8
		{
			volume, "myobject",
			7, 8,
			[]byte("world"),
			io.ErrUnexpectedEOF,
		},

 *  Fix: Don't leak file handles when a cache disk write fails.

 *  Fix: Don't hang when the public suffix database cannot be loaded. We had a bug where a failure
    reading the public suffix database would cause subsequent reads to hang when they should have
    crashed.

 *  Fix: Avoid `InetAddress.getCanonicalHostName()` in MockWebServer. This avoids problems if the

Beispielsweise können Sie [„with“ verwenden, um eine Datei auszulesen](https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files):

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

        firstLineMap.put("index", firstLineInnerMap);

        final Map<String, Object> secondLine = new HashMap<>();

        secondLine.put("text", item.getText());

        // reading
        final String[][] readings = item.getReadings();
        for (int i = 0; i < readings.length; i++) {
            secondLine.put("reading_" + i, readings[i]);
        }

    withLock {
      if (this.errorCode == null) {
        this.errorCode = errorCode
        notifyAll()
      }
    }
  }

  /**
   * Returns true if read timeouts should be enforced while reading response headers or body bytes.
   * We always do timeouts in the HTTP server role. For clients, we only do timeouts after the
   * request is transmitted. This is only interesting for duplex calls where the request and