print(df['date'].values.astype('<M8[h]'))
['2016-12-06T102016-12-06T102016-12-06T092016-12-06T092016-12-06T092016-12-06T112016-12-06T102016-11-06T092016-11-06T092016-11-06T09'
    ]
print(df.groupby(df['date'].values.astype('<M8[h]')).Item.unique())
Pandas groupпо часам дня в словарь