Executing User Entered Code?

[Bob]

Hi,
I'm writing a network simulator using Python and Tkinter.  I'd like to
be able to allow the user to enter the code for the routing algorithm
in Python and then execute it for each node during the simulation.

Can anyone point me in the right direction here?  I've looked through
most of the docs and haven't been able to find what I'm looking for.

Thanks,
-Bob