fastapi_datamodel.py

from pydantic import BaseModel

class Item(BaseModel):
    name: str
    price: float
    quantity: int
    
@app.put("/update/{item_id}")
async def update_item(item_id: int, item: Item) -> Response:
    return JSONResponse({
        "item_id": item_id,
        "item_name": item.name,
        "item_price": item.price,
        "item_quantity": item.quantity
    })