1In [1]: df = pd.DataFrame( {'a':['A','A','B','B','B','C'], 'b':[1,2,5,5,4,6]})
2 df
3
4Out[1]:
5 a b
60 A 1
71 A 2
82 B 5
93 B 5
104 B 4
115 C 6
12
13In [2]: df.groupby('a')['b'].apply(list)
14Out[2]:
15a
16A [1, 2]
17B [5, 5, 4]
18C [6]
19Name: b, dtype: object
20
21In [3]: df1 = df.groupby('a')['b'].apply(list).reset_index(name='new')
22 df1
23Out[3]:
24 a new
250 A [1, 2]
261 B [5, 5, 4]
272 C [6]