from typing import Union

from fastapi import Body, FastAPI
from pydantic import BaseModel

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: Item = Body(
        examples=[
            {
                "name": "Foo",

그리고 결과 객체에 대해서는 에디터의 도움을 받을 수 있게 됩니다.

Pydantic 공식 문서 예시:

```Python
{!../../docs_src/python_types/tutorial011.py!}
```

/// info | "정보"

Pydantic<에 대해 더 배우고 싶다면 <a href="https://docs.pydantic.dev/" class="external-link" target="_blank">공식 문서</a>를 참고하세요.</a>

///

**FastAPI**는 모두 Pydantic을 기반으로 되어 있습니다.

////

//// tab | 🐍 3️⃣.1️⃣0️⃣ & 🔛

```Python hl_lines="20"
{!> ../../docs_src/body_multiple_params/tutorial002_py310.py!}
```

////

👉 💼, **FastAPI** 🔜 👀 👈 📤 🌅 🌘 1️⃣ 💪 🔢 🔢 (2️⃣ 🔢 👈 Pydantic 🏷).

, ⚫️ 🔜 ⤴️ ⚙️ 🔢 📛 🔑 (🏑 📛) 💪, & ⌛ 💪 💖:

```JSON
{
    "item": {
        "name": "Foo",
        "description": "The pretender",
        "price": 42.0,
        "tax": 3.2
    },

from typing import List, Optional

from fastapi import FastAPI
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/valid", response_model=Item)
def get_valid():
    return {"name": "valid", "price": 1.0}


@app.get("/items/coerce", response_model=Item)

///

`RequestValidationError` 是 Pydantic 的 <a href="https://docs.pydantic.dev/latest/concepts/models/#error-handling" class="external-link" target="_blank">`ValidationError`</a> 的子类。

**FastAPI** 调用的就是 `RequestValidationError` 类，因此，如果在 `response_model` 中使用 Pydantic 模型，且数据有错误时，在日志中就会看到这个错误。

但客户端或用户看不到这个错误。反之，客户端接收到的是 HTTP 状态码为 `500` 的「内部服务器错误」。

这是因为在*响应*或代码（不是在客户端的请求里）中出现的 Pydantic `ValidationError` 是代码的 bug。

from typing import List, Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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


@app.post("/items/")
async def create_item(item: Item) -> Item:
    return item


@app.get("/items/")
async def read_items() -> List[Item]:

* Fix handling of enums with their own schema in path parameters. To support [pydantic/pydantic#1432](https://github.com/pydantic/pydantic/pull/1432) in FastAPI. PR [#1463](https://github.com/tiangolo/fastapi/pull/1463).

## 0.55.0

* Allow enums to allow them to have their own schemas in OpenAPI. To support [pydantic/pydantic#1432](https://github.com/pydantic/pydantic/pull/1432) in FastAPI. PR [#1461](https://github.com/tiangolo/fastapi/pull/1461).

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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


class ResponseMessage(BaseModel):
    message: str


class User(BaseModel):
    username: str
    email: str


@app.post("/items/", response_model=ResponseMessage, tags=["items"])
async def create_item(item: Item):
    return {"message": "Item received"}

from typing import Annotated, Union

from fastapi import Body, FastAPI
from pydantic import BaseModel

app = FastAPI()


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


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


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

from datetime import datetime

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Subscription(BaseModel):
    username: str
    monthly_fee: float
    start_date: datetime


@app.webhooks.post("new-subscription")
def new_subscription(body: Subscription):
    """
    When a new user subscribes to your service we'll send you a POST request with this