name: str | None = None
    description: str | None = None
    price: 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": []},
}


@app.get("/items/{item_id}", response_model=Item)

                            "price": {
                                "title": "Price",
                                "type": "number",
                            },
                            "tax": {
                                "title": "Tax",
                                "anyOf": [{"type": "number"}, {"type": "null"}],
                            },
                            "tags": {

    - **name**: each item must have a name
    - **description**: a long description
    - **price**: required
    - **tax**: if the item doesn't have tax, you can omit this
    - **tags**: a set of unique tag strings for this item
    """

                            "price": {
                                "title": "Price",
                                "type": "number",
                            },
                            "tax": {
                                "title": "Tax",
                                "anyOf": [{"type": "number"}, {"type": "null"}],
                            },
                            "tags": {

    price: float
    tax: float | None = None
    tags: set[str] = set()


@app.post("/items/", summary="Create an item")
async def create_item(item: Item) -> Item:
    """
    Create an item with all the information:

    - **name**: each item must have a name
    - **description**: a long description
    - **price**: required
    - **tax**: if the item doesn't have tax, you can omit this

            "price": 35.4,
            "tax": 3.2,
            "tags": ["foo", "bar", "foo"],
        },
    )
    assert response.status_code == 200, response.text
    assert response.json() == {
        "item_id": 123,
        "item": {
            "name": "Foo",
            "description": "A very nice Item",
            "price": 35.4,
            "tax": 3.2,
            "tags": tags_expected,
        },

```JSON hl_lines="2"
{
    "item": {
        "name": "Foo",
        "description": "The pretender",
        "price": 42.0,
        "tax": 3.2
    }
}
```

instead of:

```JSON
{
    "name": "Foo",
    "description": "The pretender",
    "price": 42.0,
    "tax": 3.2
}
```

## Recap { #recap }

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None
    tags: set[str] = set()


@app.post(
    "/items/",
    summary="Create an item",
    description="Create an item with all the information, name, description, price, tax and a set of unique tags",
)
async def create_item(item: Item) -> Item:

```JSON hl_lines="2"
{
    "item": {
        "name": "Foo",
        "description": "The pretender",
        "price": 42.0,
        "tax": 3.2
    }
}
```

而不是：

```JSON
{
    "name": "Foo",
    "description": "The pretender",
    "price": 42.0,
    "tax": 3.2
}
```

## 小結 { #recap }

即便一個請求只能有單一主體，你仍可在你的路徑操作函式中宣告多個 Body 參數。

즉, `PUT`으로 항목 `bar`를 업데이트하면서 다음과 같은 body를 보낸다면:

```Python
{
    "name": "Barz",
    "price": 3,
    "description": None,
}
```

이미 저장된 속성 `"tax": 20.2`가 포함되어 있지 않기 때문에, 입력 모델은 `"tax": 10.5`라는 기본값을 사용하게 됩니다.

그리고 데이터는 그 “새로운” `tax` 값 `10.5`로 저장됩니다.

## `PATCH`로 부분 업데이트하기 { #partial-updates-with-patch }