How can I map the headers to columns in pandas?

Question

I have a dataframe like :

A    B    C 
1    0    0
1    1    0
0    1    0
0    0    1

I want to have :

 A    B    C  lab         


        

Answer 1

Here is an idiomatic and performant solution

df['label'] = np.where(df, df.columns, '').sum(axis=1)

   A  B  C label
0  1  0  0     A
1  1  1  0    AB
2  0  1  0     B
3  0  0  1     C