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": {

### `Union` 🐍 3️⃣.1️⃣0️⃣

👉 🖼 👥 🚶‍♀️ `Union[PlaneItem, CarItem]` 💲 ❌ `response_model`.

↩️ 👥 🚶‍♀️ ⚫️ **💲 ❌** ↩️ 🚮 ⚫️ **🆎 ✍**, 👥 ✔️ ⚙️ `Union` 🐍 3️⃣.1️⃣0️⃣.

🚥 ⚫️ 🆎 ✍ 👥 💪 ✔️ ⚙️ ⏸ ⏸,:

```Python
some_variable: PlaneItem | CarItem
```

✋️ 🚥 👥 🚮 👈 `response_model=PlaneItem | CarItem` 👥 🔜 🤚 ❌, ↩️ 🐍 🔜 🔄 🎭 **❌ 🛠️** 🖖 `PlaneItem` & `CarItem` ↩️ 🔬 👈 🆎 ✍.

## 📇 🏷

///

//// tab | Python 3.10+

```Python hl_lines="1  14-15  18-20  33"
{!> ../../docs_src/extra_models/tutorial003_py310.py!}
```

////

//// tab | Python 3.8+

                        "size": {"title": "Size", "type": "integer"},
                    },
                },
                "CarItem": {
                    "title": "CarItem",
                    "required": IsOneOf(
                        ["description", "type"],
                        # TODO: remove when deprecating Pydantic v1
                        ["description"],

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": {

                        "size": {"title": "Size", "type": "integer"},
                    },
                },
                "CarItem": {
                    "title": "CarItem",
                    "required": IsOneOf(
                        ["description", "type"],
                        # TODO: remove when deprecating Pydantic v1
                        ["description"],

///

//// tab | Python 3.8 and above

```Python hl_lines="1  14-15  18-20  33"
{!> ../../docs_src/extra_models/tutorial003.py!}
```

////

///

//// tab | Python 3.10+

```Python hl_lines="1  14-15  18-20  33"
{!> ../../docs_src/extra_models/tutorial003_py310.py!}
```

////

/// note | "笔记"

定义 <a href="https://docs.pydantic.dev/latest/concepts/types/#unions" class="external-link" target="_blank">`Union`</a> 类型时，要把详细的类型写在前面，然后是不太详细的类型。下例中，更详细的 `PlaneItem` 位于 `Union[PlaneItem，CarItem]` 中的 `CarItem` 之前。

///

//// tab | Python 3.10+

```Python hl_lines="1  14-15  18-20  33"
{!> ../../docs_src/extra_models/tutorial003_py310.py!}
```

////

//// tab | Python 3.8+