Question

Consider these pseudo models:

class BaseProduct:
   quantity_available = Integer

class Box(BaseProduct):
   items_in_box = Integer

>> BaseProduct.objects.count()
>> Integer

But how do I retrieve the total number of products, so:

for each object[quantity_available * items_in_box] * total_objects

Solution:

I used Simeon Visser’s ‘sum’ as a partial solution, adding a property to the Base class:

@property
def _box_count(self):
    try:
        return self.items_in_box * self.quantity_available
    except AttributeError:
        return self.quantity_available

sum([item._box_count for item in BaseProduct.objects.all()])

Answer 1

Try the following:

sum([box.quantity_available * box.items_in_box for box in Box.objects.all()]

It retrieves all the boxes and for each box, it computes the quanitity available of that box times the number of items in boxes of that type. Lastly, it sums all these values so you get the total number of products.