from fastapi import Body, FastAPI
from pydantic import BaseModel

app = FastAPI()


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


@app.put("/items/{item_id}")
async def update_item(
    *,
    item_id: int,
    item: Item = Body(
        openapi_examples={
            "normal": {
                "summary": "A normal example",

    return client


@needs_py310
@pytest.mark.parametrize(
    "path,headers,expected_status,expected_response",
    [
        ("/items", None, 200, {"strange_header": None}),
        ("/items", {"X-Header": "notvalid"}, 200, {"strange_header": None}),
        (
            "/items",
            {"strange_header": "FastAPI test"},
            200,
            {"strange_header": "FastAPI test"},
        ),

                    "msg": "Field required",
                    "input": None,
                },
                {
                    "type": "missing",
                    "loc": ["header", "x-token"],
                    "msg": "Field required",
                    "input": None,
                },
            ]
        }
    ) | IsDict(

        "item_id": 5,
        "item": {
            "name": "Foo",
            "price": 50.5,
            "description": None,
            "tax": None,
        },
        "q": "bar",
    }


@needs_py310
def test_post_no_body_q_bar(client: TestClient):
    response = client.put("/items/5?q=bar", json=None)
    assert response.status_code == 200
    assert response.json() == {"item_id": 5, "q": "bar"}


@needs_py310

/// note

FastAPI will know that the value of `q` is not required because of the default value `= None`.

The `str | None` (Python 3.10+) or `Union` in `Union[str, None]` (Python 3.8+) is not used by FastAPI to determine that the value is not required, it will know it's not required because it has a default value of `= None`.

        elt = self.element.find('sts:{}'.format(name), _STS_NS)
        return STSElement(self.root_name, elt) if elt is not None else None

    def get_child_text(self, name, strict=True):
        """Extract text of a child element. If strict, and child element is
        not present, raises InvalidXMLError and otherwise returns
        None.

        """
        if strict:
            try:

}

#result .site cite {
	color: #093;
	font-style: normal;
}

#result .more {
	display: none;
}

#result .info {
	font-size: 80%;
}

#result .url-copy {
	color: #007bff;
}

#result .url-copied {
	color: #2c974b;
}

#result .favorited {
	display: none;
}

#result .favorited i {
	color: #fab005;
}

#result .thumbnail {
	width: 100px;

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    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": []},
}

    return client


@needs_py310
def test_create_item(client: TestClient) -> None:
    response = client.post("/items/", json={"name": "Foo"})
    assert response.status_code == 200, response.text
    assert response.json() == {"name": "Foo", "description": None}


@needs_py310
def test_read_items(client: TestClient) -> None:
    response = client.get("/items/")
    assert response.status_code == 200, response.text

## 선택적 매개변수

같은 방법으로 기본값을 `None`으로 설정하여 선택적 매개변수를 선언할 수 있습니다:

```Python hl_lines="9"
{!../../docs_src/query_params/tutorial002.py!}
```

이 경우 함수 매개변수 `q`는 선택적이며 기본값으로 `None` 값이 됩니다.

/// check | "확인"

**FastAPI**는 `item_id`가 경로 매개변수이고 `q`는 경로 매개변수가 아닌 쿼리 매개변수라는 것을 알 정도로 충분히 똑똑합니다.

///

/// note | "참고"

FastAPI는 `q`가 `= None`이므로 선택적이라는 것을 인지합니다.