from dataclasses import dataclass
from inspect import signature, Parameter
 
def lax_dataclass(cls_or_None=None, **kwargs):
    def decorator(cls):
        def __init__(self, *args, **kwargs):
            orig_init(self, *args, **{
                name: value for name, value in kwargs.items() if name in accepted_keywords
            })
        cls = dataclass(**kwargs)(cls)
        orig_init = cls.__init__
        accepted_keywords = {
            param.name for param in signature(orig_init).parameters.values()
            if param.kind in (Parameter.POSITIONAL_OR_KEYWORD, Parameter.KEYWORD_ONLY)
        }
        cls.__init__ = __init__
        return cls
    if cls_or_None is None:
        return decorator
    return decorator(cls_or_None)
 
@lax_dataclass
class MyClass:
    a: int
 
print(MyClass(20, **{"kwarg1" : 1}))

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