django annotate sum condition code example

Example 1: sum values in django models

sum_a = sum([item.column for item in queryset]) # Definitely takes more memory.
sum_b = queryset.aggregate(Sum('column')).get('column__sum') # Takes about 20% more time.

Example 2: sum values in django models and insert value in model field

# models.py
def total_amount_spent(self):
    temp_values = [int(user.amount_spent) for user in ExtendedProfile.objects.all()]
    return sum(temp_values)