import copy
from dataclasses import dataclass, field, InitVar, replace
 
@dataclass
class D:
    a: float = 10.                # Normal attribute with a default value
    b: InitVar[float] = 20.       # init-only attribute with a default value 
    c: float = field(init=False)  # an attribute that will be defined in __post_init__
 
    def __post_init__(self, b):
        self.c = self.a + b
 
 
def copy_dataclass(D_class, d_obj):
    input = {}
    for key, value in d_obj.__dict__.items():
        # If the attribute is passed to __init__
        if d_obj.__dataclass_fields__[key].init:
            input[key] = copy.deepcopy(value)
 
    copy_d = D_class(**input)
 
    return copy_d
d1 = D(1, 2)
d2 = copy_dataclass(D, d1)
print(d1, d2)

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