Le paramètre de requête `q` a pour type `Union[str, None]` (ou `str | None` en Python 3.10), signifiant qu'il est de type `str` mais pourrait aussi être égal à `None`, et bien sûr, la valeur par défaut est `None`, donc **FastAPI** saura qu'il n'est pas requis.

/// note

**FastAPI** saura que la valeur de `q` n'est pas requise grâce à la valeur par défaut `= None`.

        String str1 = request.getResumeFrom();
        if (properties.containsKey(REMAINING_PROJECTS) && !(str1 != null && !str1.isEmpty())) {
            String propertyValue = properties.getProperty(REMAINING_PROJECTS);
            Stream.of(propertyValue.split(PROPERTY_DELIMITER))
                    .filter(str -> str != null && !str.isEmpty())

{!../../docs_src/python_types/tutorial009.py!}
```

Using `Optional[str]` instead of just `str` will let the editor help you detect errors where you could be assuming that a value is always a `str`, when it could actually be `None` too.

`Optional[Something]` is actually a shortcut for `Union[Something, None]`, they are equivalent.

This also means that in Python 3.10, you can use `Something | None`:

//// tab | Python 3.10+

Skopiuj to do pliku `main.py`.

Uruchom serwer:

<div class="termy">

```console
$ uvicorn main:app --reload

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
<span style="color: green;">INFO</span>:     Started reloader process [28720]
<span style="color: green;">INFO</span>:     Started server process [28722]

<div class="termy">

```console
$ fastapi run main.py --root-path /api/v1

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

</div>

If you use Hypercorn, it also has the option `--root-path`.

/// note | "Technical Details"

The ASGI specification defines a `root_path` for this use case.

<div class="termy">

```console
$ OPENAPI_URL= uvicorn main:app

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

</div>

Then if you go to the URLs at `/openapi.json`, `/docs`, or `/redoc` you will just get a `404 Not Found` error like:

```JSON
{
    "detail": "Not Found"
}

	ADD	R4, R5			// a5101000
	ADDV	R4, R5			// a5901000
	AND	R4, R5			// a5901400
	NEGW	R4, R5			// 05101100
	NEGV	R4, R5			// 05901100
	SLL	R4, R5			// a5101700
	SLL	R4, R5, R6		// a6101700
	SRL	R4, R5			// a5901700
	SRL	R4, R5, R6	 	// a6901700
	SRA	R4, R5			// a5101800
	SRA	R4, R5, R6	 	// a6101800
	ROTR	R4, R5			// a5101b00
	ROTR	R4, R5, R6		// a6101b00
	SLLV	R4, R5			// a5901800
	SLLV	R4, R5, R6		// a6901800

	LUI	$524287, X15				// b7f7ff7f

	SLL	X6, X5, X7				// b3936200
	SLL	X5, X6					// 33135300
	SLL	$1, X5, X6				// 13931200
	SLL	$1, X5					// 93921200
	SRL	X6, X5, X7				// b3d36200
	SRL	X5, X6					// 33535300
	SRL	$1, X5, X6				// 13d31200
	SRL	$1, X5					// 93d21200

	SUB	X6, X5, X7				// b3836240
	SUB	X5, X6					// 33035340
	SUB	$-2047, X5, X6				// 1383f27f
	SUB	$2048, X5, X6				// 13830280

### Executar o App

Você pode executar o app:

<div class="termy">

```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>

Então, vá para a interface `/docs`, você verá que o **FastAPI** está usando esses **modelos** para **documentar** a API, e ele também os usará para **serializar** e **validar** os dados.

<font color="#4E9A06">INFO</font>:     Will watch for changes in these directories: [&apos;/home/user/code/awesomeapp&apos;]
<font color="#4E9A06">INFO</font>:     Uvicorn running on <b>http://127.0.0.1:8000</b> (Press CTRL+C to quit)
<font color="#4E9A06">INFO</font>:     Started reloader process [<font color="#34E2E2"><b>2265862</b></font>] using <font color="#34E2E2"><b>WatchFiles</b></font>