Column Label Of Max In Pandas

I am trying to extract maximum value in row and contributing column label from pandas dataframe. For example, A B C D index x 0 1 2 3 y 3 2 1 0 I expect the follow

Solution 1:

Need axis='columns' or axis=1 in DataFrame.idxmax:

df['Con'] = df.idxmax(axis='columns')
print (df)
       A  B  C  D  Maxv Con
index                      
x      0  1  2  3     3   D
y      3  2  1  0     3   A

Or:

df['Con'] = df.idxmax(axis=1)
print (df)
       A  B  C  D  Maxv Con
index                      
x      0  1  2  3     3   D
y      3  2  1  0     3   A

You get NaNs, because data are not align to index:

print (df.idxmax(axis='rows'))
A    y
B    y
C    x
D    x
dtype: object