pydantic：如果提交的 B 符合某些条件，则将提交的 A 设为可选

Question

假设我有一个

studen

t 模型，我想要的是：如果

age

< 6, make the

school

可选。

我能做什么？预先感谢！

from pydantic import BaseModel

class Student(BaseModel):
    name: str
    age: int
    school: str

student = Student(**{ "name": "Tom", "age": 10, "school": "Blabla"}) # validated
baby_student = Student(**{ "name": "Tom", "age": 5}) # expected to be validated

我尝试过的：

from pydantic import BaseModel, root_validator

class Student(BaseModel):
    name: str
    age: int
    school: str
    
    @root_validator(pre=True)
    def ignore_school_if_baby(cls, values):
        age = values.get("age")
        if age < 6:
            # don't know how to do here
            values["school"] = None
        return values

baby_student = Student(**{ "name": "Tom", "age": 5})

ValidationError: 1 validation error for Student
school
  none is not an allowed value (type=type_error.none.not_allowed)

也尝试了以下方法，但仍然出现相同的错误

from typing import Optional

    @root_validator(pre=True)
    def ignore_school_if_baby(cls, values):
        age = values.get("age")
        if age < 6:
            annotations = cls.__annotations__
            annotations["school"] = Optional[annotations["school"]]
            cls.__annotations__ = annotations
        return values

Answer 1

from pydantic import BaseModel, root_validator


class Student(BaseModel):
    name: str
    age: int
    school: str

    @root_validator(pre=True)
    def ignore_school_if_baby(cls, values):
        age = values.get("age")
        if age < 6:
            cls.__fields__['school'].required = False
            
        return values

baby_student = Student(**{ "name": "Tom", "age": 5})

我的笨蛋，我认为

cls.__fields__['school'].required = False

有效

Answer 2

您可以将

school

包裹成

Optional

类型。
另外给你一个建议，如果仍然提供

values["school"] = None

，

school

将替换数据。，

values["school"] = values.get("school")

可以避免这个问题。

class Student(BaseModel):
    name: str
    age: int
    school: Optional[str]

    @root_validator(pre=True)
    def ignore_school_if_baby(cls, values):
        age = values.get("age")
        if age < 6:
            values["school"] = values.get("school")
        return values