Pandas: groupby column A and make lists of tuples from other columns?

Make a new column for amount-time tuple atpair

 df['atpair'] = list(zip(df.amount, df.time))

The data frame looks like

        user  time  amount       atpair
    0     1    20   10.99  (10.99, 20)
    1     1    10    4.99   (4.99, 10)
    2     2    11    2.99   (2.99, 11)
    3     2    18    1.99   (1.99, 18)
    4     3    15   10.99  (10.99, 15)

Now perform groupby and apply list append to atpair

 df = df.groupby('user')['atpair'].apply(lambda x : x.values.tolist())

The data frame looks like

user
1    [(10.99, 20), (4.99, 10)]
2     [(2.99, 11), (1.99, 18)]
3                [(10.99, 15)]

apply(list) will consider the series index not the values .I think you are looking for

df.groupby('user')[['time', 'amount']].apply(lambda x: x.values.tolist())

user
1    [[23.0, 2.99], [50.0, 1.99]]
2                  [[12.0, 1.99]]