Python nested defaultdict

example_inline.py

>>> bb = nested_defaultdict({'a':{'b': 1000}})
>>> bb['c']['e']['f']['g'] = 2000
>>> bb
defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'a': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'b': 1000}), 'c': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'e': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'f': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'g': 2000})})})})
>>> bb['a']['c']['f']['g'] = 3000
>>> bb
defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'a': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'b': 1000, 'c': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'f': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'g': 3000})})}), 'c': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'e': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'f': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'g': 2000})})})})
>>> import json
>>> json.dumps(bb)
'{"a": {"b": 1000, "c": {"f": {"g": 3000}}}, "c": {"e": {"f": {"g": 2000}}}}'
>>> bb = nested_defaultdict()
>>> bb
defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {})
>>> bb['a']['c']['f']['g'] = 3000
>>> bb
defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'a': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'c': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'f': defaultdict(<function nested_defaultdict at 0x7fcb514bcb70>, {'g': 3000})})})})

nested_defaultdict_example.py

def nested_defaultdict(existing=None, **kwargs):
    if existing is None:
        existing = {}
    if not isinstance(existing, dict):
        return existing
    existing = {key: nested_defaultdict(val) for key, val in existing.items()}
    return defaultdict(nested_defaultdict, existing, **kwargs)