python - Data Aggregation in Django Model -

this model concerned:

class order(models.model):     guest = models.foreignkey('hotel.guest', on_delete=models.cascade)     date = models.datefield(auto_now_add=true)     amount = models.integerfield()     item = models.foreignkey('hotel.item', on_delete=models.cascade)     price = models.integerfield(default=1)     is_paid = models.booleanfield(default=false)     paid_date = models.datefield(blank=true, null=true) 

my current view returns list specific guest of unpaid orders:

open_orders = order.objects.filter(guest = guest, is_paid=false). 

i aggregate amount , price per item , date list in new list...

the documentation explains how aggregations across entire queryset, , annotations across relationship seem stuck this...

i used .values('item_id','date').annotate(sum('amount')).annotate(sum('price')) doesn't seem right.

data example:

open_orders =  (date=11/11/2011,guest=john,amount=2,item=beer,price = 30 = order.amount * order.item.price, is_paid = false, paid_date null), (11/11/2011,john,4,beer,60,false,null), (11/11/2011,john,2,wine,50,false,null),  (11/12/2011,john,2,beer,30,false,null),  (11/12/2011,john,1,wine,25,false,null),  (11/12/2011,john,8,wine,200,false,null) 

the desired output be

(11/11/2011,john,6,beer,90,false,null), (11/11/2011,john,2,wine,50,false,null),  (11/12/2011,john,2,beer,30,false,null),  (11/12/2011,john,9,wine,225,false,null)