FastAPI weiß, dass der Wert von `q` nicht erforderlich ist, aufgrund des definierten Defaultwertes `= None`.

Das `str | None` (Python 3.10+) oder `Union` in `Union[str, None]` (Python 3.9+) wird von FastAPI nicht verwendet, um zu bestimmen, dass der Wert nicht erforderlich ist. FastAPI weiß, dass er nicht erforderlich ist, weil er einen Defaultwert von `= None` hat.

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 # remove this key if you do not want versioning feature # # 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...

@app.put("/items/{item_id}")
async def read_items(
    item_id: UUID,
    start_datetime: datetime = Body(),
    end_datetime: datetime = Body(),
    process_after: timedelta = Body(),
    repeat_at: Union[time, None] = Body(default=None),
):
    start_process = start_datetime + process_after
    duration = end_datetime - start_process
    return {
        "item_id": item_id,
        "start_datetime": start_datetime,

app = FastAPI()


@app.get("/hidden_cookie")
async def hidden_cookie(
    hidden_cookie: Optional[str] = Cookie(default=None, include_in_schema=False),
):
    return {"hidden_cookie": hidden_cookie}


@app.get("/hidden_header")
async def hidden_header(
    hidden_header: Optional[str] = Header(default=None, include_in_schema=False),
):
    return {"hidden_header": hidden_header}


@app.get("/hidden_path/{hidden_path}")

查询参数的值就是：

* `skip=20`：在 URL 中设定的值
* `limit=10`：使用默认值

## 可选参数

同理，把默认值设为 `None` 即可声明**可选的**查询参数：

{* ../../docs_src/query_params/tutorial002_py310.py hl[7] *}

本例中，查询参数 `q` 是可选的，默认值为 `None`。

/// check | 检查

注意，**FastAPI** 可以识别出 `item_id` 是路径参数，`q` 不是路径参数，而是查询参数。

///

/// note | 笔记

因为默认值为 `= None`，FastAPI 把 `q` 识别为可选参数。

    assert response.json() == {
        "item_id": 5,
        "item": {
            "name": "Foo",
            "description": None,
            "price": 35.4,
            "tax": None,
            "tags": [],
            "image": None,
        },
    }


def test_put_empty_body(client: TestClient):
    response = client.put(
        "/items/5",
        json={},
    )

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):

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float = 10.5


items = {
    "foo": {"name": "Foo", "price": 50.2},
    "bar": {"name": "Bar", "description": "The Bar fighters", "price": 62, "tax": 20.2},
    "baz": {
        "name": "Baz",
        "description": "There goes my baz",

class FooBaseModel(BaseModel):
    model_config = ConfigDict(extra="forbid")


class Foo(FooBaseModel):
    pass


app = FastAPI()


@app.post("/")
async def post(
    foo: Union[Foo, None] = None,
):
    return foo


client = TestClient(app)


def test_call_invalid():
    response = client.post("/", json={"foo": {"bar": "baz"}})
    assert response.status_code == 422

Deleting the cache when it is no longer needed can be done.  However this may delete the purpose of the cache
which is designed to persist between app restarts.

```kotlin
cache.delete()
```
 
## Pruning the Cache

Pruning the entire Cache to clear space temporarily can be done using evictAll.

```kotlin
cache.evictAll()
```

Removing individual items can be done using the urls iterator.