主体 - 字段¶
与您可以在路径操作函数参数中使用Query、Path和Body声明额外验证和元数据的方式相同，您也可以使用 Pydantic 的Field在 Pydantic 模型内部声明验证和元数据。
导入 Field¶
首先，您需要导入它
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}")
async def update_item(item_id: int, item: Annotated[Item, Body(embed=True)]):
results = {"item_id": item_id, "item": item}
return results
from typing import Annotated, Union
from fastapi import Body, FastAPI
from pydantic import BaseModel, Field
app = FastAPI()
class Item(BaseModel):
name: str
description: Union[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: Union[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
from typing import Union
from fastapi import Body, FastAPI
from pydantic import BaseModel, Field
from typing_extensions import Annotated
app = FastAPI()
class Item(BaseModel):
name: str
description: Union[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: Union[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
提示
如果可能，请优先使用Annotated版本。
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}")
async def update_item(item_id: int, item: Item = Body(embed=True)):
results = {"item_id": item_id, "item": item}
return results
提示
如果可能，请优先使用Annotated版本。
from typing import Union
from fastapi import Body, FastAPI
from pydantic import BaseModel, Field
app = FastAPI()
class Item(BaseModel):
name: str
description: Union[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: Union[float, None] = None
@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item = Body(embed=True)):
results = {"item_id": item_id, "item": item}
return results
警告
注意，Field是直接从pydantic导入的，而不是像其他所有 (Query、Path、Body等) 一样从fastapi导入。
声明模型属性¶
然后，您可以在模型属性中使用Field
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}")
async def update_item(item_id: int, item: Annotated[Item, Body(embed=True)]):
results = {"item_id": item_id, "item": item}
return results
from typing import Annotated, Union
from fastapi import Body, FastAPI
from pydantic import BaseModel, Field
app = FastAPI()
class Item(BaseModel):
name: str
description: Union[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: Union[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
from typing import Union
from fastapi import Body, FastAPI
from pydantic import BaseModel, Field
from typing_extensions import Annotated
app = FastAPI()
class Item(BaseModel):
name: str
description: Union[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: Union[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
提示
如果可能，请优先使用Annotated版本。
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}")
async def update_item(item_id: int, item: Item = Body(embed=True)):
results = {"item_id": item_id, "item": item}
return results
提示
如果可能，请优先使用Annotated版本。
from typing import Union
from fastapi import Body, FastAPI
from pydantic import BaseModel, Field
app = FastAPI()
class Item(BaseModel):
name: str
description: Union[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: Union[float, None] = None
@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item = Body(embed=True)):
results = {"item_id": item_id, "item": item}
return results
Field的工作方式与Query、Path和Body相同，它具有所有相同的参数等。
"技术细节"
实际上，您将在后面看到的Query、Path等，会创建通用Param类的子类的对象，而Param本身是 Pydantic 的FieldInfo类的子类。
而 Pydantic 的Field也会返回一个FieldInfo实例。
Body也会直接返回FieldInfo子类的对象。您将在后面看到其他一些是Body类的子类。
请记住，当您从fastapi导入Query、Path和其他内容时，它们实际上是返回特殊类的函数。
提示
注意，每个带有类型、默认值和Field的模型属性，都具有与路径操作函数参数相同的结构，只是使用Field代替Path、Query和Body。
添加额外信息¶
您可以在Field、Query、Body等中声明额外信息。它将包含在生成的 JSON Schema 中。
您将在后面的文档中学习更多关于添加额外信息的知识，届时您将学习如何声明示例。
警告
传递给Field的额外键也将出现在应用程序的最终 OpenAPI 模式中。由于这些键可能不是 OpenAPI 规范的一部分，因此某些 OpenAPI 工具（例如OpenAPI 验证器）可能无法使用您生成的模式。
回顾¶
您可以使用 Pydantic 的Field为模型属性声明额外的验证和元数据。
您还可以使用额外的关键字参数传递其他 JSON Schema 元数据。