How to get unique values from multiple columns in a pandas groupby

Question

Starting from this dataframe df:

df = pd.DataFrame({\'c\':[1,1,1,2,2,2],\'l1\':[\'a\',\'a\',\'b\',\'c\',\'c\',\'b\'],\'l2\':[\'b\',\'d\',\'d\',\'f\',\'e\',\'f\']         


        

Answer 1

You can do it with apply:

import numpy as np
g = df.groupby('c')['l1','l2'].apply(lambda x: list(np.unique(x)))

Answer 2

Alternatively, you can use agg:

g = df.groupby('c')['l1','l2'].agg(['unique'])