[Django]-Access django database on postgresql from independent python script

I think the best way is to build an API layer to exchange data between your Django and your externals. Django rest framework provides a really simply solution to add a REST layer to your app that is also reusable with any other external.
https://www.django-rest-framework.org/

With this approach you centralize and abstract the direct database manipulation in Django, avoiding any external operation that may break it’s consistency (for example with an alter table).