Python 數據類：強制字典字段為深拷貝

Question

我正在使用包含字典的數據類。

我希望 dict 成為一個深層副本，而不必依賴post_init調用，這基本上會使數據類失去興趣

什么是好的解決方案？

from dataclasses import dataclass, field
from typing import Dict


@dataclass
class ClassWithDict:
    the_dict: Dict = field(default_factory=dict, kw_only=True)


toto = {"toto": "tata"}
the_class = ClassWithDict(the_dict=toto)

assert toto == the_class.the_dict
assert toto is not the_class.the_dict  # FALSE

Answer 1

解決方案，如果不想使用__post__init__使用object.setattr方法在初始化 object 后強制復制，則使用metaclass ：

import copy
from dataclasses import dataclass, field
from typing import Dict


class DataClassWithDeepCopyMeta(type):

    def __call__(cls, *args, **kwargs):
        args = copy.deepcopy(args)
        kwargs = copy.deepcopy(kwargs)
        return super().__call__(*args, **kwargs)


@dataclass
class ClassWithDict(metaclass=DataClassWithDeepCopyMeta):
    the_dict: Dict = field(default_factory=dict)


toto = {"toto": "tata"}
the_class = ClassWithDict(toto)

assert toto == the_class.the_dict
assert toto is not the_class.the_dict