nested_dict

nested_dict extends defaultdict to support python dict with multiple levels of nested-ness:

Iterating through nested_dict

Iterating through deep or unevenly nested dictionaries is a bit of a pain without recursion. nested dict allows you to flatten the nested levels into tuples before iteration.

You do not need to know beforehand how many levels of nesting you have:

from nested_dict import nested_dict
nd= nested_dict()
nd["one"] = "1"
nd[1]["two"] = "1 / 2"
nd["uno"][2]["three"] = "1 / 2 / 3"

for keys_as_tuple, value in nd.items_flat():
    print ("%-20s == %r" % (keys_as_tuple, value))

#   (1, 'two')           == '1 / 2'
#   ('one',)             == '1'
#   ('uno', 2, 'three')  == '1 / 2 / 3'

nested_dict provides

• items_flat()

• keys_flat()

• values_flat()

(iteritems_flat(), iterkeys_flat(), and itervalues_flat() are python 2.7-style synonyms. )

Converting to / from dictionaries

The magic of nested_dict sometimes gets in the way (of pickleing for example).

We can convert to and from a vanilla python dict using

• nested_dict.to_dict()

• nested_dict constructor

>>> from nested_dict import nested_dict
>>> nd= nested_dict()
>>> nd["one"] = 1
>>> nd[1]["two"] = "1 / 2"

#
#   convert nested_dict -> dict and pickle
#
>>> nd.to_dict()
{1: {'two': '1 / 2'}, 'one': 1}
>>> import pickle
>>> binary_representation = pickle.dumps(nd.to_dict())

#
#   convert dict -> nested_dict
#
>>> normal_dict = pickle.loads(binary_representation)
>>> new_nd = nested_dict(normal_dict)
>>> nd == new_nd
True

defaultdict

nested_dict extends collections.defaultdict

You can get arbitrarily-nested “auto-vivifying” dictionaries using defaultdict.

from collections import defaultdict
nested_dict = lambda: defaultdict(nested_dict)
nd = nested_dict()
nd[1][2]["three"][4] = 5
nd["one"]["two"]["three"][4] = 5

However, only nested_dict supports a dict of dict of sets etc.