/// note | "技术细节"

也可以使用 `from starlette import status` 导入状态码。

**FastAPI** 的`fastapi.status` 和 `starlette.status` 一样，只是快捷方式。实际上，`fastapi.status` 直接继承自 Starlette。

///

## `tags` 参数

`tags` 参数的值是由 `str` 组成的 `list` （一般只有一个 `str` ），`tags` 用于为*路径操作*添加标签：

```Python hl_lines="17  22  27"
{!../../docs_src/path_operation_configuration/tutorial002.py!}
```

OpenAPI 概图会自动添加标签，供 API 文档接口使用：

from fastapi import FastAPI
from fastapi.exceptions import ResponseValidationError
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: Optional[float] = None
    owner_ids: Optional[List[int]] = None


@app.get("/items/invalid", response_model=Item)
def get_invalid():
    return {"name": "invalid", "price": "foo"}

```Python
from datetime import date

from pydantic import BaseModel

# Declaras la variable como un str
# y obtienes soporte del editor dentro de la función
def main(user_id: str):
    return user_id


# Un modelo de Pydantic
class User(BaseModel):
    id: int
    name: str
    joined: date
```

Este puede ser usado como:

```Python

```Python
from datetime import date

from pydantic import BaseModel

# Declare uma variável como str
# e obtenha suporte do editor dentro da função
def main(user_id: str):
    return user_id


# Um modelo do Pydantic
class User(BaseModel):
    id: int
    name: str
    joined: date
```

Que então pode ser usado como:

```Python

    protected static String urlEncode(final String str) {
        if (str == null) {
            return StringUtil.EMPTY;
        }
        return URLEncoder.encode(str, Constants.UTF_8_CHARSET);
    }

    @Deprecated
    protected static String urlDecode(final String str) {
        if (str == null) {
            return StringUtil.EMPTY;
        }
        return URLDecoder.decode(str, Constants.UTF_8_CHARSET);
    }

        return getName();
    }

    static String unescape( String str ) throws NumberFormatException, UnsupportedEncodingException {
        char ch;
        int i, j, state, len;
        char[] out;
        byte[] b = new byte[1];

        if( str == null ) {
            return null;
        }

        len = str.length();
        out = new char[len];
        state = 0;

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

////

* `description: Union[str, None] = None` (or `str | None = None` in Python 3.10) has a default of `None`.
* `tax: float = 10.5` has a default of `10.5`.
* `tags: List[str] = []` has a default of an empty list: `[]`.

but you might want to omit them from the result if they were not actually stored.

    return f"bar_{route.name}"


def custom_generate_unique_id3(route: APIRoute):
    return f"baz_{route.name}"


class Item(BaseModel):
    name: str
    price: float


class Message(BaseModel):
    title: str
    description: str


def test_top_level_generate_unique_id():
    app = FastAPI(generate_unique_id_function=custom_generate_unique_id)
    router = APIRouter()

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):
    return {"item_id": item_id, "q": q}


@app.put("/items/{item_id}")

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):
    return {"item_id": item_id, "q": q}


@app.put("/items/{item_id}")