django Sum 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: django group by

# If you mean to do aggregation you can use the aggregation features of the ORM:
from django.db.models import Count
Members.objects.values('designation').annotate(dcount=Count('designation'))

# This results in a query similar to:
SELECT designation, COUNT(designation) AS dcount
FROM members GROUP BY designation

#and the output would be of the form
[{'designation': 'Salesman', 'dcount': 2}, 
 {'designation': 'Manager', 'dcount': 2}]