I am running into an issue where adding new columns to a multiindex column DataFrame causes the new columns to append to the end of the DataFrame. E.g.:
Group 1 | Group 2 | Group 1 | Group 2 |
------------------------------------------------------
Sub 1 | Sub 2 | Sub 1 | Sub 2 | New Sub | New Sub |
Whereas what I want is:
Group 1 | Group 2 |
------------------------------------------------------
Sub 1 | Sub 2 | New Sub | Sub 1 | Sub 2 | New Sub |
Is there a way to re-group/order my multiindex to do this? Note- I do not want to re-order the Sub Groups by name, as New Sub needs to go at the end, and alphabetically might not sort correctly.
I think you need reindex or reindex_axis by custom list:
df1=pd.DataFrame(columns=pd.MultiIndex.from_product((('C','R', 'A'),(1,2))),
data=np.arange(6).reshape(1,-1))
df2=pd.DataFrame(columns=pd.MultiIndex.from_tuples((('C','3'),('R',5),('A',4))),
data=[[9,9,4]])
df=df1.join(df2)
print (df)
C R A C R A
1 2 1 2 1 2 3 5 4
0 0 1 2 3 4 5 9 9 4
df1 = df.reindex(columns = ['C','R','A'], level=0)
print (df1)
C R A
1 2 3 1 2 5 1 2 4
0 0 1 9 2 3 9 4 5 4
df1 = df.reindex_axis(['C','R','A'], level=0, axis=1)
print (df1)
C R A
1 2 3 1 2 5 1 2 4
0 0 1 9 2 3 9 4 5 4