Arbitrarily nested dictionary from tuples

Question

Given a dictionary with tuples as keys (and numbers/scalars as values), what is a Pythonic way to convert to a nested dictionary? The hitch is that from input-to-input, the

Answer 1

You can use itertools.groupby with recursion:

from itertools import groupby
def create_nested_dict(d):
  _c = [[a, [(c, d) for (_, *c), d in b]] for a, b in groupby(sorted(d, key=lambda x:x[0][0]), key=lambda x:x[0][0])]
  return {a:b[0][-1] if not any([c for c, _ in b]) else create_nested_dict(b) for a, b in _c}

---

from itertools import product

d1 = dict(zip(product('AB', [0, 1]), range(2*2)))
d2 = dict(zip(product('AB', [0, 1], [True, False]), range(2*2*2)))
d3 = dict(zip(product('CD', [0, 1], [True, False], 'AB'), range(2*2*2*2)))
print(create_nested_dict(d1.items()))
print(create_nested_dict(d2.items()))
print(create_nested_dict(d3.items())) 

Output:

{'A': {0: 0, 1: 1}, 'B': {0: 2, 1: 3}}
{'A': {0: {False: 1, True: 0}, 1: {False: 3, True: 2}}, 'B': {0: {False: 5, True: 4}, 1: {False: 7, True: 6}}}
{'C': {0: {False: {'A': 2, 'B': 3}, True: {'A': 0, 'B': 1}}, 1: {False: {'A': 6, 'B': 7}, True: {'A': 4, 'B': 5}}}, 'D': {0: {False: {'A': 10, 'B': 11}, True: {'A': 8, 'B': 9}}, 1: {False: {'A': 14, 'B': 15}, True: {'A': 12, 'B': 13}}}}