Pydantic使用默认函数设置属性

from datetime import datetime, timedelta
from pydantic import BaseModel

class User(BaseModel):
    id: int
    name: str
    join_date: datetime = None

    @classmethod
    def get_default_join_date(cls):
        return datetime.now() - timedelta(days=180)

    def __init__(__pydantic_self__, **data: any):
        super().__init__(**data)
        if __pydantic_self__.join_date is None:
            __pydantic_self__.join_date = cls.get_default_join_date()

# 创建一个用户实例，设置 `join_date` 为默认值
user1 = User(id=1, name="Alice")
print(user1)  # 输出：User id=1 name='Alice' join_date=datetime.datetime(2021, 9, 2, 12, 38, 27.678633)

# 创建另一个用户实例，显式设置 `join_date`
user2 = User(id=2, name="Bob", join_date=datetime.now())
print(user2)  # 输出：User id=2 name='Bob' join_date=datetime.datetime(2021, 9, 2, 12, 38, 27.678633)