Nested dictionary to multiindex dataframe where dictionary keys are column labels

问题

Say I have a dictionary that looks like this:

dictionary = {\'A\' : {\'a\': [1,2,3,4,5],
                     \'b\': [6,7,8,9,1]},

              \'B\' : {\'a\': [2,3,4,5,6],
                     \'b\': [7,8,9,1,2]}}

and I want a dataframe that looks something like this:

     A   B
     a b a b
  0  1 6 2 7
  1  2 7 3 8
  2  3 8 4 9
  3  4 9 5 1
  4  5 1 6 2

Is there a convenient way to do this? If I try:

In [99]:

DataFrame(dictionary)

Out[99]:
     A               B
a   [1, 2, 3, 4, 5] [2, 3, 4, 5, 6]
b   [6, 7, 8, 9, 1] [7, 8, 9, 1, 2]

I get a dataframe where each element is a list. What I need is a multiindex where each level corresponds to the keys in the nested dict and the rows corresponding to each element in the list as shown above. I think I can work a very crude solution but I\'m hoping there might be something a bit simpler.

回答1:

Pandas wants the MultiIndex values as tuples, not nested dicts. The simplest thing is to convert your dictionary to the right format before trying to pass it to DataFrame:

>>> reform = {(outerKey, innerKey): values for outerKey, innerDict in dictionary.iteritems() for innerKey, values in innerDict.iteritems()}
>>> reform
{('A', 'a'): [1, 2, 3, 4, 5],
 ('A', 'b'): [6, 7, 8, 9, 1],
 ('B', 'a'): [2, 3, 4, 5, 6],
 ('B', 'b'): [7, 8, 9, 1, 2]}
>>> pandas.DataFrame(reform)
   A     B   
   a  b  a  b
0  1  6  2  7
1  2  7  3  8
2  3  8  4  9
3  4  9  5  1
4  5  1  6  2

[5 rows x 4 columns]

回答2:

dict_of_df = {k: pd.DataFrame(v) for k,v in dictionary.items()}
df = pd.concat(dict_of_df, axis=1)

Note that the order of columns is lost for python < 3.6

来源：https://stackoverflow.com/questions/24988131/nested-dictionary-to-multiindex-dataframe-where-dictionary-keys-are-column-label