Django queryset SUM 正负值

Question

I have a model which have IntegerField named as threshold. I need to get total SUM of threshold value regardless of negative values.

vote_threshold

100

-200

-5

result = 305

Right now I am doing it like this.

earning = 0
result = Vote.objects.all().values('vote_threshold')
            for v in result:
                if v.vote_threshold >  0:
                    earning += v.vote_threshold
                else:
                    earning -= v.vote_threshold

What is a faster and more proper way?

Answer 1

use abs function in django

from django.db.models.functions import Abs
from django.db.models import Sum
<YourModel>.objects.aggregate(s=Sum(Abs("vote_threshold")))

Answer 2

try this:

objects = Vote.objects.extra(select={'abs_vote_threshold': 'abs(vote_threshold)'}).values('abs_vote_threshold')
earning = sum([obj['abs_vote_threshold'] for obj in objects])

Answer 3

I don't think there is an easy way to do the calculation using the Django orm. Unless you have performance issues, there is nothing wrong with doing the calculation in python. You can simplify your code slightly by using sum() and abs() .

votes = Vote.objects.all()
earning = sum(abs(v.vote_threshold) for v in votes) 

If performance is an issue, you can use raw SQL .

from django.db import connection

cursor = connection.cursor()
cursor.execute("SELECT sum(abs(vote_theshold)) from vote")
row = cursor.fetchone()
earning = row[0]

Answer 4

This one example, if you want to sum negative and positive in one query

select = {'positive': 'sum(if(value>0, value, 0))', 
          'negative': 'sum(if(value<0, value, 0))'}
summary = items.filter(query).extra(select=select).values('positive', 'negative')[0]
positive, negative = summary['positive'], summary['negative']