Django : Case statement

Many of you might be using case statement in SQL. How do we do this in Django ?

Let us first look at an example of SQL Case statement

SELECT
    blog_product.id,
    blog_product.name,
    blog_product.price,
    blog_product.category
FROM blog_product
WHERE blog_product.id IN (4, 2, 1, 3, 5)
ORDER BY
    CASE
        WHEN blog_product.id = 4 THEN 1
        WHEN blog_product.id = 2 THEN 2
        WHEN blog_product.id = 1 THEN 3
        WHEN blog_product.id = 3 THEN 4
        WHEN blog_product.id = 5 THEN 5
        ELSE NULL
    END ASC;

To handle this in django, below is the solution:

from django.db.models import Case, When
from .models import Product, Order

# Notice how we want to sort the products by the ids of the orders
order_ids = [4, 2, 1, 3, 5]
products = Product.objects.all()

preferred = Case(
    *(
        When(order__id=id, then=pos)
        for pos, id in enumerate(order_ids, start=1)
    )
)
products_sorted = products.filter(order__id__in=order_ids).order_by(preferred)