nk20/apps/note/tables.py

#!/usr/bin/env python
import django_tables2 as tables
from django.db.models import F

from .models.transactions import Transaction


class HistoryTable(tables.Table):
    class Meta:
        attrs = {
            'class':
            'table table-bordered table-condensed table-striped table-hover'
        }
        model = Transaction
        template_name = 'django_tables2/bootstrap.html'
        sequence = ('...', 'total', 'valid')

    total = tables.Column()  #will use Transaction.total() !!

    def order_total(self, QuerySet, is_descending):
        # needed for rendering
        QuerySet = QuerySet.annotate(
            total=F('amount') *
            F('quantity')).order_by(('-' if is_descending else '') + 'total')
        return (QuerySet, True)