Örneğin, bir şeyin `str` ya da `None` olabileceğini şöyle belirtebilirsiniz:

```python
from typing import Union


def say_hi(name: Union[str, None]):
        print(f"Hi {name}!")
```

`typing`, bir şeyin `None` olabileceğini belirtmek için `Optional` ile bir kısayol da sunar.

from dataclasses import dataclass, field

from fastapi import FastAPI


@dataclass
class Item:
    name: str
    price: float
    tags: list[str] = field(default_factory=list)
    description: str | None = None
    tax: float | None = None


app = FastAPI()


@app.get("/items/next", response_model=Item)
async def read_next_item():
    return {
        "name": "Island In The Moon",
        "price": 12.99,

   * Converts the specified {@code String str} from this format to the specified {@code format}. A
   * "best effort" approach is taken; if {@code str} does not conform to the assumed format, then
   * the behavior of this method is undefined but we make a reasonable effort at converting anyway.
   */
  public final String to(CaseFormat format, String str) {
    checkNotNull(format);
    checkNotNull(str);

    for item_def in cast(dict[str, dict[str, Any]], definitions).values():
        if "description" in item_def:
            item_description = cast(str, item_def["description"]).split("\f")[0]
            item_def["description"] = item_description
    # definitions: dict[DefsRef, dict[str, Any]]
    # but mypy complains about general str in other places that are not declared as

    val name = truncateName(subprojects.joinToString(","))

    private fun truncateName(str: String) =
        // Can't exceed Linux file name limit 255 char on TeamCity
        if (str.length > 200) {
            str.substring(0, 200) + "..."
        } else {
            str
        }

    override fun createFunctionalTestsFor(
        model: CIBuildModel,
        stage: Stage,

    void testToString() {
        NbtException e = new NbtException(NbtException.ERR_SSN_SRVC, NbtException.NO_RESOURCES);
        String str = e.toString();
        assertTrue(str.contains("errorClass=2"));
        assertTrue(str.contains("errorCode=" + NbtException.NO_RESOURCES));
        assertTrue(str.contains("Called name present, but insufficient resources"));
    }

    code.
    """

    def __init__(
        self,
        *,
        openIdConnectUrl: Annotated[
            str,
            Doc(
                """
            The OpenID Connect URL.
            """
            ),
        ],
        scheme_name: Annotated[
            str | None,
            Doc(
                """
                Security scheme name.

    }
}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: str | None = None


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


class UserInDB(User):
    hashed_password: str


password_hash = PasswordHash.recommended()

```Python hl_lines="1"
async def needy_dependency(fresh_value: Annotated[str, Depends(get_value, use_cache=False)]):
    return {"fresh_value": fresh_value}
```

////

//// tab | Python 3.10+ без Annotated

/// tip | Порада

Надавайте перевагу версії з `Annotated`, якщо це можливо.

///

```Python hl_lines="1"
async def needy_dependency(fresh_value: str = Depends(get_value, use_cache=False)):

from starlette.status import HTTP_401_UNAUTHORIZED


class APIKeyBase(SecurityBase):
    model: APIKey

    def __init__(
        self,
        location: APIKeyIn,
        name: str,
        description: str | None,
        scheme_name: str | None,
        auto_error: bool,
    ):
        self.auto_error = auto_error

        self.model: APIKey = APIKey(
            **{"in": location},  # ty: ignore[invalid-argument-type]