如何优雅地访问和修改Python中深度嵌套的字典？

class dotdictify(dict):
    def __init__(self, value=None):
        if value is None:
            pass
        elif isinstance(value, dict):
            for key in value:
                self.__setitem__(key, value[key])
        else:
            raise TypeError('expected dict')

    def __setitem__(self, key, value):
        if '.' in key:
            parts = key.split('.', 1)
            target = self.setdefault(parts[0], dotdictify())
            if not isinstance(target, dotdictify):
                raise KeyError(f'Cannot set "{parts[1]}" in "{parts[0]}" ({repr(target)})')
            target[parts[1]] = value
        else:
            if isinstance(value, dict) and not isinstance(value, dotdictify):
                value = dotdictify(value)
            dict.__setitem__(self, key, value)

    def __getitem__(self, key):
        if '.' not in key:
            return dict.__getitem__(self, key)
        parts = key.split('.', 1)
        target = dict.__getitem__(self, parts[0])
        if not isinstance(target, dotdictify):
            raise KeyError(f'Cannot get "{parts[1]}" in "{parts[0]}" ({repr(target)})')
        return target[parts[1]]

    def __contains__(self, key):
        if '.' not in key:
            return dict.__contains__(self, key)
        parts = key.split('.', 1)
        target = dict.__getitem__(self, parts[0])
        if not isinstance(target, dotdictify):
            return False
        return parts[1] in target

    def setdefault(self, key, default):
        if key not in self:
            self[key] = default
        return self[key]

    __setattr__ = __setitem__
    __getattr__ = __getitem__