[Answer]-Simple reverse in query in django

Your question is hard to understand, so I’ll look at a couple of interpretations:

1. You want to get countries for a particular post:

   countries = Country.objects.filter(post=post_instance)
   

2. You want to get all countries that have any posts:

   countries = Country.objects.filter(post__isnull=False)
   

   Similarly, if you wanted to get countries that don’t have a post associated with them:

   countries = Country.objects.filter(post__isnull=True)