1.py

class Parent(object):
    conf = {}

    def __init__(self, *args, **kwargs):
        type(self).conf = defaultdict(
            None, **super(type(self), self).conf)
        super(Parent, self).__init__(*args, **kwargs)

    @classmethod
    def set_param(cls, name, value):
        cls.conf[name] = value


class Child(Parent):
    pass