from fastapi import FastAPI
from fastapi.openapi.docs import (
    get_redoc_html,
    get_swagger_ui_html,
    get_swagger_ui_oauth2_redirect_html,
)

app = FastAPI(docs_url=None, redoc_url=None)


@app.get("/docs", include_in_schema=False)
async def custom_swagger_ui_html():
    return get_swagger_ui_html(
        openapi_url=app.openapi_url,
        title=app.title + " - Swagger UI",

    return {"item_id": item_id, "item": item}


@app.head("/items/{item_id}")
def head_item(item_id: str):
    return JSONResponse(None, headers={"x-fastapi-item-id": item_id})


@app.options("/items/{item_id}")
def options_item(item_id: str):
    return JSONResponse(None, headers={"x-fastapi-item-id": item_id})


@app.patch("/items/{item_id}")
def patch_item(item_id: str, item: Item):

## 응답 모델 인코딩 매개변수

응답 모델은 아래와 같이 기본값을 가질 수 있습니다:

```Python hl_lines="11  13-14"
{!../../docs_src/response_model/tutorial004.py!}
```

* `description: Optional[str] = None`은 기본값으로 `None`을 갖습니다.
* `tax: float = 10.5`는 기본값으로 `10.5`를 갖습니다.
* `tags: List[str] = []` 빈 리스트의 기본값으로: `[]`.

그러나 실제로 저장되지 않았을 경우 결과에서 값을 생략하고 싶을 수 있습니다.

        width: 300px;
        height: 50px;
        padding: 2px;
        font-family: Verdana, sans-serif;
        font-size: 10pt;
        color: #000000;
        text-decoration: none;
    }
    a.plain {
        display: inline;
        float: none;
        width: auto;
        height: auto;
    }
    a.sort {
        display: block;
        float: left;
        width: 100px;
        height: 15px;

`Optional[EenType]` is eigenlijk een snelkoppeling voor `Union[EenType, None]`, ze zijn equivalent.

Dit betekent ook dat je in Python 3.10 `EenType | None` kunt gebruiken:

//// tab | Python 3.10+

```Python hl_lines="1"
{!> ../../docs_src/python_types/tutorial009_py310.py!}

(prefers-reduced-motion: reduce) {\n  .btn {\n    transition: none;\n  }\n}\n\n.btn:hover {\n  color: #212529;\n  text-decoration: none;\n}\n\n.btn:focus, .btn.focus {\n  outline: 0;\n  box-shadow: none;\n}\n\n.btn.disabled, .btn:disabled {\n  opacity: 0.65;\n  box-shadow: none;\n}\n\n.btn:not(:disabled):not(.disabled) {\n  cursor: pointer;\n}\n\n.btn:not(:disabled):not(.disabled):active, .btn:not(:disabled):not(.disabled).active {\n  box-shadow: none;\n}\n\na.btn.disabled,\nfieldset:disabled a.btn {\n  pointer-events:...

			if tc.error == "" && err != nil {
				t.Fatalf("expected no error, got %v", err)
			}
			if tc.error != "" {
				if err == nil {
					t.Fatalf("expected error to include \"%s\" but got none", tc.error)
				}
				if !strings.Contains(err.Error(), tc.error) {
					t.Fatalf("expected \"%s\" in error, got %v", tc.error, err)
				}
			}

			commandOutput := out.String()

</div>

This means that it will **always have a value**, it's just that sometimes the value could be `None` (or `null` in JSON).

That means that, clients using your API don't have to check if the value exists or not, they can **assume the field will always be there**, but just that in some cases it will have the default value of `None`.

The way to describe this in OpenAPI, is to mark that field as **required**, because it will always be there.

/// tip | Dica

Fazer com que o modelo de retorno garanta que um valor esteja sempre disponível e sempre seja um `int` (não `None`) é muito útil para os clientes da API, eles podem escrever código muito mais simples com essa certeza.

    "bar": {"id": "bar", "title": "Bar", "description": "The bartenders"},
}

app = FastAPI()


class Item(BaseModel):
    id: str
    title: str
    description: Union[str, None] = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token: