annotate in django code example

Example 1: 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}]

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)