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);

/// info

Before, this page used to list links to external articles.

But now that FastAPI is the backend framework with the most GitHub stars across languages, and the most starred and used framework in Python, it no longer makes sense to attempt to list all articles written about it.

///

## GitHub Repositories

    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)):