你也可以在 Python **之外**的終端機中建立環境變數（或使用其他方法），然後在 Python 中**讀取**它們。

例如，你可以建立一個名為 `main.py` 的檔案，其中包含以下內容：

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip

第二個參數是 [`os.getenv()`](https://docs.python.org/3.8/library/os.html#os.getenv) 的預設回傳值。

如果沒有提供，預設值為 `None`，這裡我們提供 `"World"` 作為預設值。

///

然後你可以呼叫這個 Python 程式：

Por ejemplo, podrías tener un archivo `main.py` con:

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip | Consejo

El segundo argumento de [`os.getenv()`](https://docs.python.org/3.8/library/os.html#os.getenv) es el valor por defecto a retornar.

Por ejemplo, [puedes usar `with` para leer un archivo](https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files):

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

Internamente, `open("./somefile.txt")` crea un objeto llamado "Context Manager".

Cuando el bloque `with` termina, se asegura de cerrar el archivo, incluso si hubo excepciones.

   * Function<Integer, Double> sqrt = (Integer in) -> Math.sqrt((int) in);
   * Map<String, Double> transformed = Maps.transformValues(map, sqrt);
   * System.out.println(transformed);
   * }
   *
   * ... prints {@code {a=2.0, b=3.0}}.
   *
   * <p>Changes in the underlying map are reflected in this view. Conversely, this view supports
   * removal operations, and these are reflected in the underlying map.
   *

   * Function<Integer, Double> sqrt = (Integer in) -> Math.sqrt((int) in);
   * Map<String, Double> transformed = Maps.transformValues(map, sqrt);
   * System.out.println(transformed);
   * }
   *
   * ... prints {@code {a=2.0, b=3.0}}.
   *
   * <p>Changes in the underlying map are reflected in this view. Conversely, this view supports
   * removal operations, and these are reflected in the underlying map.
   *

        emptyMappingFile.manager(dictionaryManager);

        PagingList<CharMappingItem> result = emptyMappingFile.selectList(0, 10);

        // Debug: print what we actually got
        if (result.size() > 0) {
            for (CharMappingItem item : result) {
                System.out.println("Unexpected item: " + item.toLineString());
            }
        }

```python
from typing import Any


def some_function(data: Any):
    print(data)
```

### Types génériques { #generic-types }

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			Key:   target.MqttBroker,
			Value: cfg.Broker.String(),
		},
		config.KV{
			Key:   target.MqttTopic,
			Value: cfg.Topic,
		},
		config.KV{
			Key:   target.MqttQoS,
			Value: fmt.Sprintf("%d", cfg.QoS),
		},
		config.KV{
			Key:   target.MqttUsername,
			Value: cfg.User,
		},
		config.KV{
			Key:   target.MqttPassword,
			Value: cfg.Password,
		},
		config.KV{

	// Should only be modified before any calls are made.
	MaxErrResponseSize int64

	// Avoid metrics update if set to true
	NoMetrics bool

	// TraceOutput will print debug information on non-200 calls if set.
	TraceOutput io.Writer // Debug trace output

	httpClient *http.Client
	url        *url.URL
	auth       func() string

	sync.RWMutex // mutex for lastErr