* <abbr title="Mozilla Developer Network: documentation for developers, written by the Firefox people">MDN</abbr>
* <abbr title="Input/Output: disk reading or writing, network communications.">I/O</abbr>.

////

//// tab | Info

"title" attributes of "abbr" elements are translated following some specific instructions.

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.

Les « Context Managers » sont des objets Python que vous pouvez utiliser dans une instruction `with`.

Par exemple, [vous pouvez utiliser `with` pour lire un fichier](https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files) :

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

En coulisse, `open("./somefile.txt")` crée un objet appelé « Context Manager ».

	// Object operations.

	// GetObjectNInfo returns a GetObjectReader that satisfies the
	// ReadCloser interface. The Close method runs any cleanup
	// functions, so it must always be called after reading till EOF
	//
	// IMPORTANTLY, when implementations return err != nil, this
	// function MUST NOT return a non-nil ReadCloser.

// 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

    // in a recursive loop.  Sneaky.
    if (level == stimuli.length) {
      // We've filled the array.
      compareResultsForThisListOfStimuli();
    } else {
      // Keep recursing to fill the array.
      for (Stimulus<E, ? super I> stimulus : getStimulusValues()) {
        stimuli[level] = stimulus;
        recurse(level + 1);
      }
    }
  }

      size = 0;
      for (ValueEntry<K, V> entry = firstEntry; entry != null; entry = entry.successorInValueSet) {
        multimapIterationChain.delete(entry);
        // TODO(cpovirk): Also clear *InValueSet (after reading next) and nextInValueBucket?
      }
      firstEntry = null;
      lastEntry = null;
      modCount++;
    }
  }

  @Override
  Iterator<Entry<K, V>> entryIterator() {

      size = 0;
      for (ValueEntry<K, V> entry = firstEntry; entry != null; entry = entry.successorInValueSet) {
        multimapIterationChain.delete(entry);
        // TODO(cpovirk): Also clear *InValueSet (after reading next) and nextInValueBucket?
      }
      firstEntry = null;
      lastEntry = null;
      modCount++;
    }
  }

  @Override
  Iterator<Entry<K, V>> entryIterator() {

```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。

當 `with` 區塊結束時，它會確保關閉檔案，即使發生了例外也一樣。

當你建立一個含 `yield` 的相依時，**FastAPI** 會在內部為它建立一個情境管理器，並與其他相關工具結合。

### 在含 `yield` 的相依中使用情境管理器 { #using-context-managers-in-dependencies-with-yield }

"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)
```