Groupby To Return Nth Group - NOT Row

I'm attempting to group by two factors in a long (>2M) rows. Background to the data The second factor is effectively a test date - for a given sample (the first group) a sample

Solution 1:

You can reset_index, then use GroupBy + nth:

res = df.reset_index().groupby('id').nth(1)

print(res)

                   date        value
id                                  
1   10/01/2017 15:45:00  [0.01, 0.4]
3   06/01/2017 11:02:00        [0.1]
5   05/01/2017 10:09:00       [0.01]
6   03/02/2017 09:15:00        [0.5]
7   19/01/2017 16:34:00        [0.1]