Basically all you mentioned above can be done in modern Python. Unfortunately I've seen it done... and God, the results are horrible, in Python. "Wait did call

Basically all you mentioned above can be done in modern Python. Unfortunately I've seen it done... and God, the results are horrible, in Python. "Wait did calling this method just change the class of the object the method was on??!!!! Fuuuu..." But simple stuff like incrementally building classes method by method in eg. jupyter notebooks can be done and it's even quite clean, it's just that nobody is teaching people the techniques for doing it... (And the jupyter autoreload magic doesn't seem to like it so you'd have to "do it by hand") And sure, since Python got scoping and concurrency quite wrong, if you go full-interactive on things you'll shoot yourself in the foot faaast!