Preferred way to input python commands from the main loop

[morden]

I'm creating a simple tkinter program to get driven by an existing motif 
application.
The way I intend it to work is to have the existing app feed python 
commands to the tkinter program sitting in the mainloop, have them
executed and feed the results in form

fromgui.buttonpressed("tagfoo", 1)

back to the motif app.

Sooo, should I used after() to setup reading from the motif app or 
should I create a thread waiting for the input from the motif app?