Multi-index pivoting in Pandas
If I understand what you are asking I think what you want is pandas.pivot_table(...) which you can use like so:
table = pd.pivot_table(df, index=['item_id', 'hour', 'date'], columns='when', values='quantity')which with a sample data frame of
item_id hour when date quantity0 a 1 before 2015-01-26 251 b 1 before 2015-01-26 142 a 1 after 2015-01-26 43 d 1 before 2015-01-26 434 b 1 after 2015-01-26 305 d 1 after 2015-01-26 12produces
when after beforeitem_id hour date a 1 2015-01-26 4 25b 1 2015-01-26 30 14d 1 2015-01-26 12 43