Rearranging levels of a nested dictionary in python

Question

Is there a library that would help me achieve the task to rearrange the levels of a nested dictionary

Eg: From this:

{1:{"A":"i","B":"ii","C":"i"},2:{"B":"i","C":"ii"},3:{"A":"iii"}}

To this:

{"A":{1:"i",3:"iii"},"B":{1:"ii",2:"i"},"C":{1:"i",2:"ii"}}

ie first two levels on a 3 levelled dictionary swapped. So instead of 1 mapping to A and 3 mapping to A, we have A mapping to 1 and 3.

The solution should be practical for an arbitrary depth and move from one level to any other within.

Answer 1

>>> d = {1:{"A":"i","B":"ii","C":"i"},2:{"B":"i","C":"ii"},3:{"A":"iii"}}
>>> keys = ['A','B','C']
>>> e = {key:{k:d[k][key] for k in d if key in d[k]} for key in keys}
>>> e
{'C': {1: 'i', 2: 'ii'}, 'B': {1: 'ii', 2: 'i'}, 'A': {1: 'i', 3: 'iii'}}

thank god for dict comprehension

Answer 2

One way to think about this would be to consider your data as a (named) array and to take the transpose. An easy way to achieve this would be to use the data analysis package Pandas:

import pandas as pd

df = pd.DataFrame({1: {"A":"i","B":"ii","C":"i"},
                   2: {"B":"i","C":"ii"},
                   3: {"A":"iii"}})
df.transpose().to_dict()

{'A': {1: 'i', 2: nan, 3: 'iii'},
 'B': {1: 'ii', 2: 'i', 3: nan},
 'C': {1: 'i', 2: 'ii', 3: nan}}