Python 使用 Pydantic 父属性来验证子项

最简单的方法是在父级而不是子级上执行验证:

from pydantic import BaseModel, validator

class Item(BaseModel):
    value: int

class Container(BaseModel):
    multiplier: int
    field_1: Item
    field_2: Item


    @validator("field_1", "field_2")
    def validate_value(cls, v, values):
        """Validate each item"""
        m = values["multiplier"]

如果要在子级上定义验证器，可以创建一个函数，然后从父级调用验证函数:

class Item(BaseModel):
    value: int

    @classmethod
    def validate_value(cls, v, **kwargs):
        """Validate each item"""
        m = kwargs.get("multiplier")

        if m * v.value < 10:
            raise ValueError

        return v


class Container(BaseModel):
    multiplier: int
    field_1: Item
    field_2: Item

    @validator("field_1", "field_2", pre=False)
    def validate_items(cls, v, values):
        return Item.validate_value(v, **values)

另一种方法是将multiplier作为private model attribute传递给子对象，然后子对象可以使用PYDANIC验证函数，但您仍然需要动态赋值给子对象:

from pydantic import BaseModel, Field, validator


class Item(BaseModel):
    multiplier: int  # exclude from parent serialization, workaround for validation
    value: int

    @validator("value", pre=False)
    def validate_value(cls, v, values):
        """Validate each item"""
        m = values["multiplier"]

        if m * v < 10:
            raise ValueError

        return v


class Container(BaseModel):
    multiplier: int
    field_1: Item = Field(..., exclude={'multiplier'})
    field_2: Item = Field(..., exclude={'multiplier'})

    @validator("field_1", "field_2", pre=True)
    def validate_items(cls, v, values):
        
        # Construct from a value, another workaround
        if isinstance(v, int):
            return Item(value=v, multiplier=values["multiplier"])
        
        elif isinstance(v, Item):
            return Item(value=v.value, multiplier=values["multiplier"])


if __name__ == '__main__':

    c = Container(
        multiplier=1,
        field_1=11,
        field_2=22
    )