How to add model elements to the end of the list?

Question

Django

There is a model:

class A(models.Models):
    price = models.DecimalField(decimal_places=2, max_digits=12, default=0, verbose_name='Цена')
    stock = models.PositiveIntegerField(blank=True, default=0)

I need to check the following.
Sort by price, but at the same time, so that the elements with stock = 0 are at the end of the list.
Did it like this:

a = A.objects.all()
b = a.filter(stock__gt=0).order_by('-price')
c = a.filter(stock=0).order_by('-price')
x = set()
x.update(b)
x.update(c)
return list(x)

Only this does not work and the elements are still mixed into a heap. How to solve this problem correctly?

Answer 1

from itertools import chain
b = a.filter(stock__gt=0).order_by('-price')
c = a.filter(stock=0)
x = chain(b, c)

Can it be like this

Answer 2

All just read what set is here and the first links will give the right answer.

Answer 3

a = A.objects.all()
a.annotate(
        zero_price = Case(
            When(price=0, then=Value(1)),
            default = Value(0),
            output_field = IntegerField()
        )
    ).order_by("zero_price", "price")