```Python hl_lines="3"
import os

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

/// tip

The second argument to <a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> is the default value to return.

If not provided, it's `None` by default, here we provide `"World"` as the default value to use.

/// info

You can read more about the Starlette `lifespan` handlers in <a href="https://www.starlette.dev/lifespan/" class="external-link" target="_blank">Starlette's  Lifespan' docs</a>.

Including how to handle lifespan state that can be used in other areas of your code.

///

## Sub Applications { #sub-applications }

 * powerful advantage. Although Java offers certain immutable collection factory methods, such as
 * {@link Collections#singleton(Object)} and <a
 * href="https://docs.oracle.com/javase/9/docs/api/java/util/Set.html#immutable">{@code Set.of}</a>,
 * we recommend using <i>these</i> classes instead for this reason (as well as for consistency).
 *
 * <h4>Creation</h4>
 *

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

</div>

## 確認

次のインタラクティブなドキュメントにアクセスしてください: <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>。

下記のように見えるでしょう:

<img src="/img/tutorial/security/image01.png">

/// check | Authorizeボタン!

すでにピカピカの新しい「Authorize」ボタンがあります。

```console
$ fastapi dev main.py

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

</div>

Luego dirígete a la interfaz de `/docs`, verás que **FastAPI** está usando estos **modelos** para **documentar** la API, y los usará para **serializar** y **validar** los datos también.

<div class="screenshot">
<img src="/img/tutorial/sql-databases/image01.png">

func (s *ScanRange) Validate() error {
	if s == nil {
		return nil
	}
	if s.Start == nil && s.End == nil {
		// This parameter is optional, but when specified, it must not be empty.
		// Ref: https://docs.aws.amazon.com/AmazonS3/latest/API/API_SelectObjectContent.html#AmazonS3-SelectObjectContent-request-ScanRange
		return errors.New("ScanRange: No Start or End specified")
	}
	if s.Start == nil || s.End == nil {
		return nil

   <span style="background-color:#007166"><font color="#D3D7CF"> server </font></span>  Documentation at <font color="#729FCF"><u style="text-decoration-style:solid">http://0.0.0.0:8000/docs</u></font>

             Logs:

     <span style="background-color:#007166"><font color="#D3D7CF"> INFO </font></span>  Started server process <b>[</b><font color="#34E2E2"><b>2306215</b></font><b>]</b>

{* ../../docs_src/path_operation_advanced_configuration/tutorial005_py39.py hl[6] *}

If you open the automatic API docs, your extension will show up at the bottom of the specific *path operation*.

<img src="/img/tutorial/path-operation-advanced-configuration/image01.png">

   <span style="background-color:#007166"><font color="#D3D7CF"> server </font></span>  Documentation at <font color="#729FCF"><u style="text-decoration-style:solid">http://0.0.0.0:8000/docs</u></font>

             Logs:

     <span style="background-color:#007166"><font color="#D3D7CF"> INFO </font></span>  Started server process <b>[</b><font color="#34E2E2"><b>2306215</b></font><b>]</b>

type Status string

// Supported status types
const (
	Enabled  Status = "Enabled"
	Disabled Status = "Disabled"
)

// DeleteMarkerReplication - whether delete markers are replicated - https://docs.aws.amazon.com/AmazonS3/latest/dev/replication-add-config.html
type DeleteMarkerReplication struct {
	Status Status `xml:"Status"` // should be set to "Disabled" by default
}