Pandas group by on groupby to list of lists

Question

Given a dataframe structured like:

rule_id | ordering | sequence_id
   1    |    0     |     12     
   1    |    1     |     13
   1    |    1     |     14
   2         


        

Answer 1

Use another groupby by first level of MultiIndex:

df.groupby(['rule_id', 'ordering'])['sequence_id'].apply(list).groupby(level=0).apply(list)