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

在相依覆寫中，我們在建立新的 `Settings` 物件時設定 `admin_email` 的新值，然後回傳該新物件。

接著我們就可以測試它是否被使用。

## 讀取 `.env` 檔 { #reading-a-env-file }

如果你有許多設定，而且在不同環境中可能常常變動，將它們放在一個檔案中，然後像讀取環境變數一樣自該檔案讀取，可能會很實用。

這種作法很常見，這些環境變數通常放在 `.env` 檔中，而該檔案被稱為「dotenv」。

/// tip

在類 Unix 系統（如 Linux 與 macOS）中，以點（`.`）開頭的檔案是隱藏檔。

Na sobrescrita da dependência definimos um novo valor para `admin_email` ao criar o novo objeto `Settings`, e então retornamos esse novo objeto.

Depois podemos testar que ele é usado.

## Lendo um arquivo `.env` { #reading-a-env-file }

Se você tiver muitas configurações que possivelmente mudam bastante, talvez em diferentes ambientes, pode ser útil colocá-las em um arquivo e então lê-las como se fossem variáveis de ambiente.

// 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

    valueSetCapacity = DEFAULT_VALUE_SET_CAPACITY;
    int distinctKeys = stream.readInt();
    Map<K, Collection<V>> map = Platform.newLinkedHashMapWithExpectedSize(12);
    for (int i = 0; i < distinctKeys; i++) {
      @SuppressWarnings("unchecked")
      K key = (K) stream.readObject();
      map.put(key, createCollection(key));
    }
    int entries = stream.readInt();
    for (int i = 0; i < entries; i++) {

    valueSetCapacity = DEFAULT_VALUE_SET_CAPACITY;
    int distinctKeys = stream.readInt();
    Map<K, Collection<V>> map = Platform.newLinkedHashMapWithExpectedSize(12);
    for (int i = 0; i < distinctKeys; i++) {
      @SuppressWarnings("unchecked")
      K key = (K) stream.readObject();
      map.put(key, createCollection(key));
    }
    int entries = stream.readInt();
    for (int i = 0; i < entries; i++) {

## 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。

«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.
   *

		// 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,
		},

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)
```