But it's difficult with Python as soon as you try to do anything beyond a single module. CL and Clojure have proper packages and namespaces so it works fine. But in Python you're limited to working on the context of a single module. If you modify a module that was imported then you have to restart the REPL because you can't reload modules. It just doesn't work.

In CL I would just load the entire system then eval whatever part I want to. From that point I would never not have the current version of the system completely loaded into the running image. Much the same with emacs itself. It is a running image of your emacs lisp system and you can just modify it and eval as-you-go. Does any other language even come close to this?