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

Using dot

df.assign(label=df.dot(df.columns))

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

---

Same thing using underlying numpy arrays

df.assign(label=df.values.dot(df.columns.values))

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