```console
// Erstelle eine Umgebungsvariable MY_NAME inline für diesen Programmaufruf
$ MY_NAME="Wade Wilson" python main.py

// main.py kann jetzt diese Umgebungsvariable lesen

Hello Wade Wilson from Python

// Die Umgebungsvariable existiert danach nicht mehr
$ python main.py

Hello World from Python
```

</div>

!!! tip "Tipp"

<div class="termy">

```console
// Here we don't set the env var yet
$ python main.py

// As we didn't set the env var, we get the default value

Hello World from Python

// But if we create an environment variable first
$ export MY_NAME="Wade Wilson"

// And then call the program again
$ python main.py

// Now it can read the environment variable

Hello Wade Wilson from Python
```

### The main app file

Now we create a dependency that returns a new `config.Settings()`.

=== "Python 3.9+"

    ```Python hl_lines="6  12-13"
    {!> ../../../docs_src/settings/app02_an_py39/main.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="6  12-13"
    {!> ../../../docs_src/settings/app02_an/main.py!}
    ```

=== "Python 3.8+ non-Annotated"

    {!> ../../../docs_src/settings/app02_an_py39/main.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="6  12-13"
    {!> ../../../docs_src/settings/app02_an/main.py!}
    ```

=== "Python 3.8+ 非注解版本"

    !!! tip
        如果可能，请尽量使用 `Annotated` 版本。

    ```Python hl_lines="5  11-12"
    {!> ../../../docs_src/settings/app02/main.py!}
    ```

!!! tip
    我们稍后会讨论 `@lru_cache`。