from typing import Annotated

from fastapi import FastAPI, Path
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(
    item_id: Annotated[int, Path(title="The ID of the item to get", ge=0, le=1000)],
    q: str | None = None,
    item: Item | None = None,

from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel as BaseModelV2
from pydantic.v1 import BaseModel


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


class ItemV2(BaseModelV2):
    name: str
    description: Union[str, None] = None
    size: float


app = FastAPI()


@app.post("/items/", response_model=ItemV2)

from typing import Annotated

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

app = FastAPI()


class Item(BaseModel):
    name: str
    description: 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: float | None = None


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

from typing import Annotated, Union

from fastapi import FastAPI, Path
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: Annotated[int, Path(title="The ID of the item to get", ge=0, le=1000)],
    q: Union[str, None] = None,

{* ../../docs_src/body_multiple_params/tutorial002_py310.py hl[20] *}

У цьому випадку **FastAPI** розпізнає, що є кілька параметрів тіла (два параметри є моделями Pydantic).

Тому він використає назви параметрів як ключі (назви полів) у тілі запиту, очікуючи:

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

## Import `Field` { #import-field }

First, you have to import it:

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[4] *}


/// warning

Notice that `Field` is imported directly from `pydantic`, not from `fastapi` as are all the rest (`Query`, `Path`, `Body`, etc).

///

이 과정을 통해 코드 중복을 최소화하고, 모든 곳에서 자동 완성, 타입 검사, 에러 확인 기능이 제공되는 최적의 방식을 찾아냈습니다.

이 모든 것은 개발자들에게 최고의 개발 경험을 제공하기 위해 설계되었습니다.

---

## 필요조건

여러 대안을 테스트한 후, [Pydantic](https://docs.pydantic.dev/)을 사용하기로 결정했습니다.

이후 저는 **Pydantic**이 JSON Schema와 완벽히 호환되도록 개선하고, 다양한 제약 조건 선언을 지원하며, 여러 편집기에서의 자동 완성과 타입 검사 기능을 향상하기 위해 기여했습니다.

또한, 또 다른 주요 필요조건이었던 [Starlette](https://www.starlette.dev/)에도 기여했습니다.

---

## 개발

<img src="/img/tutorial/path-params/image02.png">

Und viele weitere kompatible Tools. Inklusive Codegenerierung für viele Sprachen.

## Pydantic { #pydantic }

Die ganze Datenvalidierung wird hinter den Kulissen von <a href="https://docs.pydantic.dev/" class="external-link" target="_blank">Pydantic</a> durchgeführt, Sie profitieren also von dessen Vorteilen. Und Sie wissen, dass Sie in guten Händen sind.

from typing import Annotated

from fastapi import Body, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


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


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

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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


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


class RecursiveItemViaSubmodel(BaseModel):
    sub_items1: list[RecursiveSubitemInSubmodel] = []
    name: str