Combine two pandas index slices-CodePudding

How can two pandas.IndexSlice s be combined into one?

Set up of the problem:

import pandas as pd
import numpy as np

idx = pd.IndexSlice
cols = pd.MultiIndex.from_product([['A', 'B', 'C'], ['x', 'y'], ['a', 'b']])
df = pd.DataFrame(np.arange(len(cols)*2).reshape((2, len(cols))), columns=cols)

df:
    A               B               C            
    x       y       x       y       x       y    
    a   b   a   b   a   b   a   b   a   b   a   b
0   0   1   2   3   4   5   6   7   8   9  10  11
1  12  13  14  15  16  17  18  19  20  21  22  23

How can the two slices idx['A', 'y', :] and idx[['B', 'C'], 'x', :], be combined to show in one dataframe?

Separately they are:

df.loc[:, idx['A', 'y',:]]
    A    
    y    
    a   b
0   2   3
1  14  15


df.loc[:, idx[['B', 'C'], 'x', :]]
    B       C    
    x       x    
    a   b   a   b
0   4   5   8   9
1  16  17  20  21

Simply combining them as a list does not play nicely:

df.loc[:, [idx['A', 'y',:], idx[['B', 'C'], 'x',:]]]
....
TypeError: unhashable type: 'slice'

My current solution is incredibly clunky, but gives the sub df that I'm looking for:

df.loc[:, df.loc[:, idx['A', 'y', :]].columns.to_list()   df.loc[:,
       idx[['B', 'C'], 'x', :]].columns.to_list()]
    A       B       C    
    y       x       x    
    a   b   a   b   a   b
0   2   3   4   5   8   9
1  14  15  16  17  20  21

However this doesn't work when one of the slices is just a series (as expected), which is less fun:

df.loc[:, df.loc[:, idx['A', 'y', 'a']].columns.to_list()   df.loc[:,
       idx[['B', 'C'], 'x', :]].columns.to_list()]
...
AttributeError: 'Series' object has no attribute 'columns'

Are there any better alternatives to what I'm currently doing that would ideally work with dataframe slices and series slices?

CodePudding user response：

General solution is join together both slice:

a = df.loc[:, idx['A', 'y', 'a']]
b = df.loc[:, idx[['B', 'C'], 'x', :]]

df = pd.concat([a, b], axis=1)
print (df)
    A   B       C    
    y   x       x    
    a   a   b   a   b
0   2   4   5   8   9
1  14  16  17  20  21