from inspect import Signature, Parameter

def r_dataclass(cls):
    # grab the annotation dict
    ann = cls.__annotations__
    # make a signature out of the keys of annotation dict
    signature = Signature([Parameter(field, Parameter.POSITIONAL_OR_KEYWORD) for field in ann])
    # define __init__ that is injected
    def __init__(self, *args, **kwargs):
		#bind the signature to arguments of constructor
        bounded = signature.bind(*args, **kwargs)
        for key, val in bounded.arguments.items():
			# set the key and value in the instance of give class
            setattr(self, key, val)
    setattr(cls, '__init__', __init__)
    return cls

# the way you use it
@r_dataclass
class Vector:
  x: float
  y: float

@r_dataclass
class Person:
  name: str
  age: int



if __name__ == '__main__':
  v = Vector(3.0, 4.3)
  print(v.x, v.y)