How apply list to a pandas group [duplicate]

Answer 1

It is well know issue with apply with list

df.groupby('c1').agg(lambda x : list(x))
Out[15]: 
           c2         c3
c1                      
A      [6, 5]     [1, 2]
B   [4, 3, 2]  [3, 4, 5]
C         [1]        [6]