import functools


def rgetattr(obj, attr, *args):

    def _getattr(obj, attr):
        return getattr(obj, attr, *args)

    return functools.reduce(_getattr, [obj] + attr.split('.'))


def rsetattr(obj, attr, val):
    pre, _, post = attr.rpartition('.')
    return setattr(rgetattr(obj, pre) if pre else obj, post, val)

# using wonder's beautiful simplification:
# https://stackoverflow.com/questions/31174295/getattr-and-setattr-on-nested-objects/31174427?noredirect=1#comment86638618_31174427


class ValidationError(Exception):
    pass