return str(obj)
    if isinstance(obj, (str, int, float, type(None))):
        return obj
    if isinstance(obj, PydanticUndefinedType):
        return None
    if isinstance(obj, dict):
        encoded_dict = {}
        allowed_keys = set(obj.keys())
        if include is not None:
            allowed_keys &= set(include)
        if exclude is not None:
            allowed_keys -= set(exclude)

Şimdi bunu FastAPI ile kullanmanın zamanı. 🚀

Şu tip anotasyonuna sahiptik:

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

Şimdi bunu `Annotated` ile saracağız; şöyle olacak:

```Python
q: Annotated[str | None] = None
```

Bu iki sürüm de aynı anlama gelir: `q`, `str` veya `None` olabilen bir parametredir ve varsayılan olarak `None`’dır.

Şimdi işin eğlenceli kısmına geçelim. 🎉

```mermaid
flowchart LR
    subgraph global[global env]
        harry-1[harry v1]
    end
    subgraph stone-project[philosophers-stone project]
        stone(philosophers-stone) -->|requires| harry-1
    end
```

    return f"{client_id}_key"


def _get_client_tag(client_id: str | None = Query(None)) -> str | None:
    if client_id is None:
        return None
    return f"{client_id}_tag"


@app.get("/foo")
def foo_handler(
    client_key: str = Depends(_get_client_key),
    client_tag: str | None = Depends(_get_client_tag),
):
    return {"client_id": client_key, "client_tag": client_tag}

この場合（`Annotated` を使わない場合）、関数内のデフォルト値 `None` を `Query()` に置き換える必要があるため、`Query(default=None)` のパラメータでデフォルト値を設定する必要があります。これは（少なくとも FastAPI にとっては）そのデフォルト値を定義するのと同じ目的を果たします。

なので:

```Python
q: str | None = Query(default=None)
```

...はデフォルト値 `None` を持つオプショナルなパラメータになり、以下と同じです:


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

ただし `Query` のバージョンでは、クエリパラメータであることを明示的に宣言しています。

class CallableGenDependency:
    def __call__(self, value: str) -> Generator[str, None, None]:
        yield value


class AsyncCallableDependency:
    async def __call__(self, value: str) -> str:
        return value


class AsyncCallableGenDependency:
    async def __call__(self, value: str) -> AsyncGenerator[str, None]:
        yield value


class MethodsDependency:

例如，你可以宣告某個值可以是 `str` 或 `None`：

```python
from typing import Union


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

在 `typing` 中也有用 `Optional` 宣告某個值可以是 `None` 的速記法。

以下是我個人（非常主觀）的建議：

* 🚨 避免使用 `Optional[SomeType]`
* 改為 ✨ 使用 `Union[SomeType, None]` ✨。

    username: str
    password: str
    email: EmailStr
    full_name: str | None = None


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


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


def fake_password_hasher(raw_password: str):
    return "supersecret" + raw_password

buckets: # # Name of the bucket # - name: bucket1 # # Policy to be set on the # # bucket [none|download|upload|public] # policy: none # # Purge if bucket exists already # purge: false # # set versioning for # # bucket [true|false] # versioning: false # # set objectlocking for # # bucket [true|false] NOTE: versioning is enabled by default if you use locking # objectlocking: false # - name: bucket2 # policy: none # purge: false # versioning: true # # set objectlocking for # # bucket [true|false] NOTE:...

    return "fakehashed" + password


oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


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


class UserInDB(User):
    hashed_password: str


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]