こんなん?

caseclass.py

#-*- coding:utf-8 -*-


class CaseClassLike(object):


    def __init__(self, **argd):

        self.__dict__.update(argd)


    def __eq__(self, other):

        if self is other:
            return True

        return self.__dict__ == other.__dict__


    def update(self, **argd):

        ret = CaseClassLike(**self.__dict__)
        ret.__dict__.update(argd)

        return ret


    def __str__(self):

        return '<CaseClass %s>' % self.__dict__


if __name__ == '__main__':

    x = CaseClassLike(a=10, b=20)
    y = CaseClassLike(a=10, b=20)

    print 'x', x
    print 'y', y

    print x == y # True
    
    z = x.update(c=10)

    print x == z # False

    print 'z', z