from typing import Union

from fastapi import Body, FastAPI
from pydantic import BaseModel
from typing_extensions import Annotated

app = FastAPI()


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


@app.put("/items/{item_id}")
async def update_item(
    *,
    item_id: int,
    item: Annotated[
        Item,
        Body(

from typing import Annotated, Union

from fastapi import Body, FastAPI
from pydantic import BaseModel, Field

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = Field(
        default=None, title="The description of the item", max_length=300
    )
    price: float = Field(gt=0, description="The price must be greater than zero")
    tax: Union[float, None] = None


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

from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class BaseItem(BaseModel):
    description: str
    type: str


class CarItem(BaseItem):
    type: str = "car"


class PlaneItem(BaseItem):
    type: str = "plane"
    size: int


items = {
    "item1": {"description": "All my friends drive a low rider", "type": "car"},
    "item2": {

from typing import List

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class RecursiveItem(BaseModel):
    sub_items: List["RecursiveItem"] = []
    name: str


RecursiveItem.update_forward_refs()


class RecursiveSubitemInSubmodel(BaseModel):
    sub_items2: List["RecursiveItemViaSubmodel"] = []
    name: str


class RecursiveItemViaSubmodel(BaseModel):

しかし、Pythonには型や「タイプパラメータ」を使ってリストを宣言する方法があります:

### typingの`List`をインポート

まず、Pythonの標準の`typing`モジュールから`List`をインポートします:

```Python hl_lines="1"
{!../../docs_src/body_nested_models/tutorial002.py!}
```

### タイプパラメータを持つ`List`の宣言

`list`や`dict`、`tuple`のようなタイプパラメータ（内部の型）を持つ型を宣言するには:

* `typing`モジュールからそれらをインストールします。
* 角括弧（`[`と`]`）を使って「タイプパラメータ」として内部の型を渡します:

```Python
from typing import List

my_list: List[str]
```

## 具有子类型的 List 字段

但是 Python 有一种特定的方法来声明具有子类型的列表：

### 从 typing 导入 `List`

首先，从 Python 的标准库 `typing` 模块中导入 `List`：

```Python hl_lines="1"
{!> ../../docs_src/body_nested_models/tutorial002.py!}
```

### 声明具有子类型的 List

要声明具有子类型的类型，例如 `list`、`dict`、`tuple`：

* 从 `typing` 模块导入它们
* 使用方括号 `[` 和 `]` 将子类型作为「类型参数」传入

```Python
from typing import List

my_list: List[str]
```

Чтобы объявить эти типы и внутренние типы, вы можете использовать стандартный Python-модуль `typing`.

Он существует специально для поддержки подсказок этих типов.

#### `List`

Например, давайте определим переменную как `list`, состоящий из `str`.

Импортируйте `List` из `typing` (с заглавной `L`):

```Python hl_lines="1"
{!../../docs_src/python_types/tutorial006.py!}
```

It would be roughly equivalent to typing:

<div class="termy">

```console
$ /opt/custompython/bin/python
```

</div>

////

//// tab | Windows

The system will **find** the `python` program in `C:\opt\custompython\bin\python` and run it.

It would be roughly equivalent to typing:

<div class="termy">

```console

from typing import Annotated

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


def fake_decode_token(token):
    return User(

from typing import Union

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


def fake_decode_token(token):
    return User(