```Python
say_hi(name=None)  # Ceci fonctionne, None est valide 🎉
```

La bonne nouvelle, c'est que, dans la plupart des cas, vous pourrez simplement utiliser `|` pour définir des unions de types :

```python
def say_hi(name: str | None):
    print(f"Hey {name}!")
```

	echo
	echo -e "${GREEN}Running test_resiliency_failure_with_server_down_and_single_disk_offline ...${NC}"
	# Stop one node
	docker stop resiliency-minio1-1
	# In additional, suspend one more disk per set in order to induce a failure
	docker exec resiliency-minio2-1 /bin/sh -c "mv /data2/.minio.sys /data2/.minio.bkp && touch /data2/.minio.sys"

            "price": 50.5,
            "description": None,
            "tax": None,
        },
        "user": {"username": "Dave", "full_name": None},
    }


def test_put_missing_body(client: TestClient):
    response = client.put("/items/5")
    assert response.status_code == 422
    assert response.json() == {
        "detail": [
            {
                "input": None,
                "loc": [

But if you have specified a custom response class with `None` as its media type, FastAPI will use `application/json` for any additional response that has an associated model.

///

## Combining information { #combining-information }

Пришло время использовать его с FastAPI. 🚀

У нас была такая аннотация типа:

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

Мы «обернём» это в `Annotated`, и получится:

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

Обе версии означают одно и то же: `q` — параметр, который может быть `str` или `None`, и по умолчанию равен `None`.

А теперь к самому интересному. 🎉

@app.get("/")
async def get():
    return HTMLResponse(html)


async def get_cookie_or_token(
    websocket: WebSocket,
    session: Annotated[str | None, Cookie()] = None,
    token: Annotated[str | None, Query()] = None,
):
    if session is None and token is None:
        raise WebSocketException(code=status.WS_1008_POLICY_VIOLATION)
    return session or token


@app.websocket("/items/{item_id}/ws")

    websocket: WebSocket,
    session: str | None = Cookie(default=None),
    token: str | None = Query(default=None),
):
    if session is None and token is None:
        raise WebSocketException(code=status.WS_1008_POLICY_VIOLATION)
    return session or token


@app.websocket("/items/{item_id}/ws")
async def websocket_endpoint(
    websocket: WebSocket,
    item_id: str,
    q: int | None = None,

# Without aliases


@app.get("/optional-str")
async def read_optional_str(p: Annotated[str | None, Cookie()] = None):
    return {"p": p}


class CookieModelOptionalStr(BaseModel):
    p: str | None = None


@app.get("/model-optional-str")
async def read_model_optional_str(p: Annotated[CookieModelOptionalStr, Cookie()]):
    return {"p": p.p}

def get_current_user(oauth_header: str | None = Security(reusable_oauth2)):
    if oauth_header is None:
        return None
    user = User(username=oauth_header)
    return user


@app.post("/login")
def login(form_data: OAuth2PasswordRequestFormStrict = Depends()):
    return form_data


@app.get("/users/me")
def read_users_me(current_user: User | None = Depends(get_current_user)):
    if current_user is None:

例如，你可以声明某个值可以是 `str` 或 `None`：

```python
from typing import Union


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

`typing` 也提供了一个声明“可能为 `None`”的快捷方式：`Optional`。

从我非常主观的角度给个小建议：

- 🚨 避免使用 `Optional[SomeType]`
- 改用 ✨`Union[SomeType, None]`✨。