[Answered ]-Django annotate with complex value

No, you can’t pass math functions into annotate().

If you want to do this calculation in Test model then create a method:

class Test(models.model):
    value = models.PositiveIntegerField(_('value'))

    def calc_value(self, next):
        return math.sqrt(next-self.value)/math.atan(self.value))

for t in Test.objects.all():
    print t.value. t.calc_value(5)

But if you want to use this calculation to order the queryset then you have to do the math at SQL level:

next = 5
Test.objects.extra(select={'new_field': 'SQRT(%d-value)/ATAN(value)' % next}) \
            .order_by('new_field'))

To filter the queryset by new field use where argument of the same extra() method:

Test.objects.extra(select={'new_field': 'SQRT(%d-value)/ATAN(value)' % next},
                   where=['new_field > 10'])

SQLite doesn’t support math functions by default but with Postgres and MySQL this code should work just fine.