// When a listener is first added, we run a task that will wait for the delegate to finish,
      // and when it is done will run the listeners.
      if (hasListeners.compareAndSet(false, true)) {
        if (delegate.isDone()) {
          // If the delegate is already done, run the execution list immediately on the current
          // thread.
          executionList.execute();
          return;
        }

    name: str = Field(index=True)
    age: Union[int, None] = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: Union[int, None] = Field(default=None, primary_key=True)
    secret_name: str


class HeroPublic(HeroBase):
    id: int


class HeroCreate(HeroBase):
    secret_name: str


class HeroUpdate(HeroBase):
    name: Union[str, None] = None
    age: Union[int, None] = None

    age: int | None = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: int | None = Field(default=None, primary_key=True)
    secret_name: str


class HeroPublic(HeroBase):
    id: int


class HeroCreate(HeroBase):
    secret_name: str


class HeroUpdate(HeroBase):
    name: str | None = None
    age: int | None = None
    secret_name: str | None = None

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

И для Python 3.10 и выше:

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

...делает параметр необязательным со значением по умолчанию `None`, также как это делает:

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

Но он явно объявляет его как query-параметр.

/// info | "Дополнительная информация"

```

Und in Python 3.10 und darüber macht:

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

... den Parameter optional, mit dem Defaultwert `None`, genauso wie:

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

Nur, dass die `Query`-Versionen den Parameter explizit als Query-Parameter deklarieren.

/// info

Bedenken Sie, dass:

```Python
= None
```

oder:

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):

class Item(BaseModel):
    name: Union[str, None] = None
    description: Union[str, None] = None
    price: Union[float, None] = None
    tax: float = 10.5
    tags: list[str] = []


items = {
    "foo": {"name": "Foo", "price": 50.2},
    "bar": {"name": "Bar", "description": "The bartenders", "price": 62, "tax": 20.2},
    "baz": {"name": "Baz", "description": None, "price": 50.2, "tax": 10.5, "tags": []},
}

	t.HealedBuckets = append(make([]string, 0, len(tracker.HealedBuckets)), tracker.HealedBuckets...)
	ahs.healStatus[tracker.ID] = t
	tracker.mu.RUnlock()
}

// Sort by zone, set and disk index
func sortDisks(disks []madmin.Disk) {
	sort.Slice(disks, func(i, j int) bool {
		a, b := &disks[i], &disks[j]
		if a.PoolIndex != b.PoolIndex {
			return a.PoolIndex < b.PoolIndex
		}

    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None
    scopes: List[str] = []


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str

    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None
    scopes: List[str] = []


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str