Permission matching query does not exist in custom permission

try:
        user = User.objects.get(username = 'xyz')
        custom_permission = Permission.objects.get(codename='is_custom')
        user.user_permissions.add(custom_permission)
        user.save()
        print user.has_perm("is_custom")
        print user.has_perm('app.is_custom')
        user.get_all_permissions()

    except Exception as e:
        print(">>>>>",e)

I have done this simple thing to check the user custom permission but it rises the exception

DoesNotExist('Permission matching query does not exist.')

what's wrong in this ??

get should return the above error if no Model object satisfies the given condition. ie, there is no Permission object with the codename is_custom. You have to modify your query like,

custom_permission = Permission.objects.filter(codename='is_custom').first() # return Permission object if exists else None
if custom_permission:
    user.user_permissions.add(custom_permission)
    user.save()