/// note | Nota

FastAPI sabrá que el valor de `q` no es requerido debido al valor por defecto `= None`.

El `str | None` (Python 3.10+) o `Union` en `Union[str, None]` (Python 3.8+) no es utilizado por FastAPI para determinar que el valor no es requerido, sabrá que no es requerido porque tiene un valor por defecto de `= None`.

Pero agregar las anotaciones de tipos permitirá que tu editor te brinde un mejor soporte y detecte errores.

	return errorResponseHandler
}

// If none of the http routes match respond with appropriate errors
func errorResponseHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method == http.MethodOptions {
		return
	}

```

`Optional[str]` ব্যবহার করা মানে হল শুধু `str` নয়, এটি হতে পারে `None`-ও, যা আপনার এডিটরকে সেই ত্রুটিগুলি শনাক্ত করতে সাহায্য করবে যেখানে আপনি ধরে নিচ্ছেন যে একটি মান সবসময় `str` হবে, অথচ এটি `None`-ও হতে পারেও।

`Optional[Something]` মূলত `Union[Something, None]`-এর একটি শর্টকাট, এবং তারা সমতুল্য।

এর মানে হল, Python 3.10-এ, আপনি টাইপগুলির ইউনিয়ন ঘোষণা করতে `Something | None` ব্যবহার করতে পারেন:

//// tab | Python 3.10+

* `limit=10`: çünkü varsayılan değer buydu.

## İsteğe Bağlı Parametreler

Aynı şekilde, varsayılan değerlerini `None` olarak atayarak isteğe bağlı parametreler tanımlayabilirsiniz:

{* ../../docs_src/query_params/tutorial002_py310.py hl[7] *}

Bu durumda, `q` fonksiyon parametresi isteğe bağlı olacak ve varsayılan değer olarak `None` alacaktır.

/// check | Ek bilgi

```Python
q: Union[str, None] = None
```

Ou como em Python 3.10 e versões superiores:

```Python
q: str | None = None
```

Por exemplo:

{* ../../docs_src/body_multiple_params/tutorial004_py310.py hl[26] *}

/// info | Informação

    assertThat(expected).hasMessageThat().contains("one");
  }

  public void testOf() {
    assertMapEquals(ImmutableBiMap.of("one", 1), "one", 1);
    assertMapEquals(ImmutableBiMap.of("one", 1).inverse(), 1, "one");
    assertMapEquals(ImmutableBiMap.of("one", 1, "two", 2), "one", 1, "two", 2);
    assertMapEquals(ImmutableBiMap.of("one", 1, "two", 2).inverse(), 1, "one", 2, "two");
    assertMapEquals(

## 선택적 매개변수

같은 방법으로 기본값을 `None`으로 설정하여 선택적 매개변수를 선언할 수 있습니다:

{* ../../docs_src/query_params/tutorial002.py hl[9] *}

이 경우 함수 매개변수 `q`는 선택적이며 기본값으로 `None` 값이 됩니다.

/// check | 확인

**FastAPI**는 `item_id`가 경로 매개변수이고 `q`는 경로 매개변수가 아닌 쿼리 매개변수라는 것을 알 정도로 충분히 똑똑합니다.

///

/// note | 참고

FastAPI는 `q`가 `= None`이므로 선택적이라는 것을 인지합니다.

    /**
     * SAX event handler called when an XML start element is encountered.
     * Processes collection definitions and tracks the element hierarchy.
     *
     * @param uri the namespace URI, or empty string if none
     * @param localName the local name without prefix, or empty string if namespace processing is not performed
     * @param qName the qualified name with prefix, or empty string if qualified names are not available

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}


@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):

    assertMapEquals(ImmutableSortedMap.of("one", 1), "one", 1);
    assertMapEquals(ImmutableSortedMap.of("one", 1, "two", 2), "one", 1, "two", 2);
    assertMapEquals(
        ImmutableSortedMap.of("one", 1, "two", 2, "three", 3), "one", 1, "three", 3, "two", 2);
    assertMapEquals(
        ImmutableSortedMap.of("one", 1, "two", 2, "three", 3, "four", 4),
        "four",
        4,
        "one",
        1,
        "three",