from dataclasses import dataclass


@dataclass
class A:
    PARAM: int


@dataclass
class B(A):
    ARG: int
    PARAM: int = 1

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "C:\Users\user\AppData\Local\Programs\Python\Python38\lib\dataclasses.py", line 1021, in dataclass
    return wrap(cls)
  File "C:\Users\user\AppData\Local\Programs\Python\Python38\lib\dataclasses.py", line 1013, in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)
  File "C:\Users\user\AppData\Local\Programs\Python\Python38\lib\dataclasses.py", line 927, in _process_class
    _init_fn(flds,
  File "C:\Users\user\AppData\Local\Programs\Python\Python38\lib\dataclasses.py", line 503, in _init_fn
    raise TypeError(f'non-default argument {f.name!r} '
TypeError: non-default argument 'ARG' follows default argument

> TypeError will be raised if a field without a default value follows a field with a default value. This is true either when this occurs in a single class, or as a result of class inheritance.

I think this is a combination of the above statement at end of [0] and inheritance following the order of the fields at [1]

[0] https://docs.python.org/3/library/dataclasses.html#dataclasses.dataclass
[1] https://docs.python.org/3/library/dataclasses.html#inheritance

See also issue36077

> I think this is a combination of the above statement at end of [0] and inheritance following the order of the fields at [1]

Ah, I see, so if I understand correctly the init method for the example given would become __init__(self, PARAM: int = 1, ARG: int) since the fields are kept in an ordered mapping

Thank you

> Ah, I see, so if I understand correctly the init method for the example given would become __init__(self, PARAM: int = 1, ARG: int) since the fields are kept in an ordered mapping

Correct.