熊猫MultiIndex更改顺序仅一级

Question

I have a dataframe with multiindex columns:

 |A    |B
 |1 |2 |1 |2
0|a  b  c  d

I would like to swap level one to get:

 |A    |B
 |2 |1 |2 |1
0|b |a |d |c

But with

df.sort_index(axis=1, level=1)

I get:

 |A|B|A|B
 |1|1|2|2
0|a|c|b|d

Please help

Many thanks

Answer 1

Assuming they have the same label, you can use reindex with level=1 :

df

   A     B   
   1  2  1  2
0  a  b  c  d

df.reindex([2, 1], level=1, axis=1)

   A     B   
   2  1  2  1
0  b  a  d  c

To generalise, you can access MultiIndex.levels :

df.reindex(df.columns.levels[1][::-1], level=1, axis=1)

   A     B   
   2  1  2  1
0  b  a  d  c

---

If the second level values are not the same for all first level labels, use

df.loc[:, ::-1].reindex(df.columns.levels[0], level=0, axis=1)

   A     B   
   2  1  2  1
0  b  a  d  c

Answer 2

Have you tried:

df.loc[:, pd.IndexSlice[:, [2, 1]]]

?

Answer 3

You still can using sort_index

df.sort_index(level=[0,1],ascending=[True,False],axis=1)
   A     B   
   2  1  2  1
0  b  a  d  c