A minimal attribute dictionary implementation using `defaultdict`

attrdict.py

from collections import defaultdict


class _attrdict(defaultdict):
    __getattr__ = defaultdict.__getitem__
    __setattr__ = defaultdict.__setitem__

    def update(self, other):
        super().update(
            (k, v) for k, v in other.items() if not issubclass(type(v), dict)
        )
        for k, v in other.items():
            if issubclass(type(v), dict):
                if k not in self or not isinstance(self[k], type(self)):
                    self[k] = attrdict()
                self[k].update(v)


def attrdict():
    return _attrdict(attrdict)