[Tutor] Halting execution

[Matthew Webber]

This has got to be trivial, but I can't find the answer ... I want to stop
execution of my main script half way through. This is just for debugging -
the code in the bottom half of the script generates a whole lot of output
that I don't want. Inserting "break" or "return" doesn't work, but something
like that is what I had in mind.
 
I'm running under ipython on windows, FWIW.
 
Thanks