Puedes **crear** y usar variables de entorno en la **shell (terminal)**, sin necesidad de Python:

//// tab | Linux, macOS, Windows Bash

<div class="termy">

```console
// Podrías crear una env var MY_NAME con
$ export MY_NAME="Wade Wilson"

// Luego podrías usarla con otros programas, como
$ echo "Hello $MY_NAME"

Hello Wade Wilson
```

</div>

////

$ $Env:MY_NAME = "Wade Wilson"

// 在其他程式中使用它，例如
$ echo "Hello $Env:MY_NAME"

Hello Wade Wilson
```

</div>

////

## 在 Python 中讀取環境變數

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

$ $Env:MY_NAME = "Wade Wilson"

// 与其他程序一起使用它，例如
$ echo "Hello $Env:MY_NAME"

Hello Wade Wilson
```

</div>

////

### 在 Python 中读取环境变量

您还可以在 Python 之外的地方（例如终端中或使用任何其他方法）创建环境变量，然后在 Python 中读取它们。

例如，您可以有一个名为 `main.py` 的文件，其中包含以下内容：

```Python hl_lines="3"
import os

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

/// tip

        //// tab | Python 3.8+ non-Annotated
        Hello
        ////
        »»»

    Result (German):

        «««
        //// tab | Python 3.8+ nicht annotiert
        Hallo
        ////
        »»»

    Source (English) – Here there is nothing to translate in the tab title:

        «««
        //// tab | Linux, macOS, Windows Bash
        Hello again
        ////
        »»»

#
#   Important for running:
#
#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
#       noncompliant, but you have some other compliant shell such as ksh or
#       bash, then to run this script, type that shell name before the whole
#       command line, like:
#
#           ksh Gradle
#
#       Busybox and similar reduced shells will NOT work, because this script

			[]byte("foo"),
		}, {
			&Header{Name: "world", Mode: 0640, Size: int64(5)},
			[]byte("hello"),
		}},
	}, {
		"GNU",
		[]file{{
			&Header{Name: "bar", Mode: 0640, Size: int64(3), Devmajor: -1},
			[]byte("foo"),
		}, {
			&Header{Name: "world", Mode: 0640, Size: int64(5), Devmajor: -1},
			[]byte("hello"),
		}},
	}, {
		"PAX",
		[]file{{

@router_a_a.get("/override", response_class=PlainTextResponse)
def get_a_a_path_override():
    return "Hello A A"


@router_a_b_override.get("/")
def get_a_b():
    return "Hello A B"


@router_a_b_override.get("/override", response_class=HTMLResponse)
def get_a_b_path_override():
    return "Hello A B"


@router_b_override.get("/")
def get_b():
    return "Hello B"

## Überschriften { #headings }

//// tab | Test

### Eine Webapp entwickeln – ein Tutorial { #develop-a-webapp-a-tutorial }

Hallo.

### Typhinweise und -annotationen { #type-hints-and-annotations }

Hallo wieder.

### Super- und Subklassen { #super-and-subclasses }

Hallo wieder.

////

//// tab | Info

  alias realpath=grealpath
  alias stat=gstat
  # By default, aliases are only expanded in interactive shells, which means
  # that they are not substituted for their corresponding commands in shell
  # scripts. By setting "expand_aliases", we enable alias expansion in
  # non-interactive shells as well.
  shopt -s expand_aliases
else
  echo '==TFCI==: Error: Cannot find path to grealpath or gstat'

    val deflater = MessageDeflater(false)
    val deflated = deflater.deflate("Hello deflate!".encodeUtf8())
    assertThat(deflated.hex()).isEqualTo("f248cdc9c95748494dcb492c49550400")
  }

  @Test fun `inflate deflate`() {
    val deflater = MessageDeflater(false)
    val inflater = MessageInflater(false)

    val goldenValue = "Hello deflate!".repeat(100).encodeUtf8()

    val deflated = deflater.deflate(goldenValue)