/// note

FastAPI will know that the value of `q` is not required because of the default value `= None`.

The `str | None` is not used by FastAPI to determine that the value is not required, it will know it's not required because it has a default value of `= None`.

But adding the type annotations will allow your editor to give you better support and detect errors.

///

from fastapi.dependencies.utils import get_typed_annotation


def test_get_typed_annotation():
    # For coverage
    annotation = "None"
    typed_annotation = get_typed_annotation(annotation, globals())

	//   return len(e) > 16 && !bytes.ContainsRune(e, '-')
	//
	// An encrypted ETag may contain some random bytes - e.g.
	// and nonce value. This nonce value may contain a '-'
	// just by its nature of being randomly generated.
	// The above implementation would incorrectly consider
	// such an ETag (with a nonce value containing a '-')
	// as non-encrypted.

	return len(e) >= 32 // We consider all ETags longer than 32 bytes as encrypted
}

app = FastAPI()


def write_log(message: str):
    with open("log.txt", mode="a") as log:
        log.write(message)


def get_query(background_tasks: BackgroundTasks, q: str | None = None):
    if q:
        message = f"found query: {q}\n"
        background_tasks.add_task(write_log, message)
    return q


@app.post("/send-notification/{email}")
async def send_notification(

     * @return RDMA provider instance, or null if none available
     */
    public static RdmaProvider getProvider(Configuration config) {
        String preference = config.getRdmaProvider();
        return createProvider(preference != null ? preference : "auto");
    }

    /**
     * Select the best available RDMA provider
     *
     * @return best RDMA provider, or null if none available
     */

from fastapi import Cookie, FastAPI

app = FastAPI()


@app.get("/items/")
async def read_items(ads_id: str | None = Cookie(default=None)):

from fastapi import FastAPI
from pydantic import BaseModel, EmailStr

app = FastAPI()


class UserBase(BaseModel):
    username: str
    email: EmailStr
    full_name: str | None = None


class UserIn(UserBase):
    password: str


class UserOut(UserBase):
    pass


class UserInDB(UserBase):
    hashed_password: str


def fake_password_hasher(raw_password: str):

</div>

Cela signifie qu'il aura **toujours une valeur**, simplement, parfois la valeur pourra être `None` (ou `null` en JSON).

Cela signifie que les clients utilisant votre API n'ont pas à vérifier si la valeur existe ou non, ils peuvent **supposer que le champ sera toujours présent**, mais que, dans certains cas, il aura la valeur par défaut `None`.

E você também pode declarar parâmetros de corpo como opcionais, definindo o valor padrão com `None`:

{* ../../docs_src/body_multiple_params/tutorial001_an_py310.py hl[18:20] *}

/// note | Nota

Repare que, neste caso, o `item` que seria capturado a partir do corpo é opcional. Visto que ele possui `None` como valor padrão.

///

## Múltiplos parâmetros de corpo { #multiple-body-parameters }

Tu modelo de response podría tener valores por defecto, como:

{* ../../docs_src/response_model/tutorial004_py310.py hl[9,11:12] *}

* `description: Union[str, None] = None` (o `str | None = None` en Python 3.10) tiene un valor por defecto de `None`.
* `tax: float = 10.5` tiene un valor por defecto de `10.5`.
* `tags: List[str] = []` tiene un valor por defecto de una list vacía: `[]`.