```Python hl_lines="4  9-12  25-27"
from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

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):

```Python hl_lines="4  9-12  25-27"
from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

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):

# | INTEGER       | java.lang.Integer    | int?          |
# | BIGINT        | java.lang.Long       | long?         |
# | REAL          | java.math.BigDecimal | decimal?      |
# | FLOAT         | java.math.BigDecimal | decimal?      |
# | DOUBLE        | java.math.BigDecimal | decimal?      |
# | DATE          | java.util.Date       | DateTime?     |
# | TIME          | java.sql.Time        | DateTime?     |

## 响应模型编码参数

你的响应模型可以具有默认值，例如：

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

* `description: Union[str, None] = None` 具有默认值 `None`。
* `tax: float = 10.5` 具有默认值 `10.5`.
* `tags: List[str] = []` 具有一个空列表作为默认值： `[]`.

但如果它们并没有存储实际的值，你可能想从结果中忽略它们的默认值。

举个例子，当你在 NoSQL 数据库中保存了具有许多可选属性的模型，但你又不想发送充满默认值的很长的 JSON 响应。

### 使用 `response_model_exclude_unset` 参数

          }
        }
      }
    ],
    "properties": {
      "anchor": {
        "type": "keyword"
      },
      "boost": {
        "type": "float"
      },
      "click_count": {
        "type": "long"
      },
      "config_id": {
        "type": "keyword"
      },
      "important_content": {
        "type": "text",

```Python hl_lines="4  9-12  25-27"
from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

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):

                                            int64_t value);
TF_CAPI_EXPORT extern void TFE_OpSetAttrFloat(TFE_Op* op, const char* attr_name,
                                              float value);
TF_CAPI_EXPORT extern void TFE_OpSetAttrBool(TFE_Op* op, const char* attr_name,
                                             unsigned char value);

                    }

                    if (!docMap.containsKey(Constants.SCORE)) {
                        final float score = hit.getScore();
                        if (Float.isFinite(score)) {
                            docMap.put(Constants.SCORE, score);
                        }
                    }

                || height < getThumbnailHtmlImageMinHeightAsInteger().intValue()) {
            return false;
        }

        final float ratio = getThumbnailHtmlImageMaxAspectRatioAsDecimal().floatValue();
        if ((float) width / (float) height > ratio || (float) height / (float) width > ratio) {
            return false;
        }

        return true;
    }

    String getHttpProxyHost();

                            <la:message key="labels.dict_kuromoji_title"/>
                        </h1>
                    </div>
                    <div class="col-sm-6">
                        <ol class="breadcrumb float-sm-right">
                            <li class="breadcrumb-item"><la:link href="/admin/dict">
                                <la:message key="labels.dict_list_link"/>
                            </la:link></li>