Hi All thanks for the comments and confirmation that this is not really possible in a Tkinter environment.
I had thought of using ncurses but was shying clear of learning about another set of widgets etc. just now. The output of the simulator is simple enough that it could just accept simple keystrokes for control, and every second or so there will be an output string saying what is happening - a sort of concatenation of the various output widgets in the Tkinter-based version. I have hoped to keep this text view so similar to the Tkinter one that it was using the same mechanisms (after(), Tk keyevents etc). Instead I think I will just write a simple mainloop() which is 'inspired by' Tkinter. I could then look at adding ncurses as a third alternative. Thanks again J^n -- https://mail.python.org/mailman/listinfo/python-list