多个请求体参数

from fastapi import FastAPI, Path, Query
from pydantic import BaseModelapp = FastAPI()class Item(BaseModel):name: strdescription: str | None = Noneprice: floattax: float | None = Noneclass User(BaseModel):username: strfull_name: str | None = None@app.put("/items")
async def update_item(item: Item, user: User):results = {"item": item, "user": user}return results

 当函数有多个请求实体（多个 Pydantic 模型参数），将使用参数名称作为请求体中的键（字段名称），并期望一个类似于以下内容的请求体

{"item": {"name": "Foo","description": "The pretender","price": 42.0,"tax": 3.2},"user": {"username": "dave","full_name": "Dave Grohl"}
}

请求体中的单一值

 假如为了拓展先前的模型，除了user和item之外，在请求体中增加一个字段importance，需要使用Body来声明，不然会被当做查询参数

from fastapi import FastAPI, Body
from pydantic import BaseModelapp = FastAPI()class Item(BaseModel):name: strdescription: str | None = Noneprice: floattax: float | None = Noneclass User(BaseModel):username: strfull_name: str | None = None@app.put("/items")
async def update_item(item: Item, user: User, importance: int = Body()):results = {"item": item, "user": user, "importance": importance}return results

{"item": {"name": "Foo","description": "The pretender","price": 42.0,"tax": 3.2},"user": {"username": "dave","full_name": "Dave Grohl"},"importance": 5
}

嵌入单个请求体实参

 假如只有一个来自的模型Item，如果你希望它期望一个拥有 item 键并在值中包含模型内容的 JSON，就像在声明额外的请求体参数时所做的那样。比如下面这样的。

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

而不是这样的。

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

则可以使用一个特殊的 Body 参数 embed

from typing import Annotatedfrom fastapi import Body, FastAPI
from pydantic import BaseModelapp = FastAPI()class Item(BaseModel):name: strdescription: str | None = Noneprice: floattax: float | None = None@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Annotated[Item, Body(embed=True)]):results = {"item_id": item_id, "item": item}return results

 声明模型属性

和使用Query，Path，Body在路径操作函数中声明参数校验和元数据的方式相同，可以使Pydantic 的Field在模型内部进行声明校验和元数据

from typing import Annotatedfrom fastapi import Body, FastAPI
from pydantic import BaseModel, Fieldapp = FastAPI()class Item(BaseModel):name: strdescription: 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}")
async def update_item(item_id: int, item: Annotated[Item, Body(embed=True)]):results = {"item_id": item_id, "item": item}return results