Django pre_save create unique slug

create_unique_slug.py

@receiver(pre_save, sender=Course)
def create_slug(sender, instance, *args, **kwargs):
    instance.slug = orig = slugify(instance.name)
    if Course.objects.filter(slug=instance.slug).exists():
        # Creates a unique slug, adding -number when its already used.
        for x in itertools.count(1):
            if not Course.objects.filter(slug=instance.slug).exists():
                break
            instance.slug = '%s-%d' % (orig, x)