Discourse is oriented the other way around. You create categories (and optionally sub-categories) and allow people to join discussions in those categories. If they want to be notified, they can set their notification preferences for each category using the blue bell.
You can create groups as well that can be @ mentioned in topics to loop them into conversations, if you like using a system like you specified eg @pythonusers (everyone using python and @python-specialists (just pythin specialists).
But ideally you’d get your category structure down first.