Exiting a Program Running in Idle, Various Choices

[W. eWatson]

I I have a  very simple program running in Python, with say the last 
line print "bye". it finishes leaving the script showing >>> in the 
shell window. The program proceeds linearly to the bottom line.

Suppose now I have instead a few lines of MatPlotLib code (MPL) like 
this at the end:

...
Show()

Show displays some graph and again the code proceeds linearly from line 
1. However, if one closes the graphic by clicking the x in the upper 
right corner of that window, then no >>> appears in the shell, and one 
must kill the shell using the x in the shell's upper right corner. A 
little dialog with the choices of OK (kill) or cancel appears. Use OK 
and the shell window disappears. A ctrl-c does nothing in the shell.

I know about sys.exit(),and a "finish" def when using Tkinter. I'm not 
using Tkinter as far as I know via MPL.

So how does one exit smoothly in this case of Show(), so that the shell 
window remains ready to entry commands?