Recursively replace nested dict(s) with your own dict subclass type.

gistfile1.py

import json
from collections import defaultdict


class D(defaultdict):
    def __init__(self, *args, **kwargs):
        if args and len(args) == 1 and isinstance(args[0], dict):
            for k, v in args[0].items():
                if isinstance(v, dict):
                    self[k] = self.__class__(v)
                else:
                    self[k] = v
        else:
            super(D, self).__init__(self.__class__, *args, **kwargs)

    def __repr__(self):
        return "D({})".format(dict.__repr__(self))


if __name__ == "__main__":
    sample = json.JSONDecoder().decode('{"a": { "b": { "c": 1 } } }')
    print(D(sample))