random keypress bounce in a terminal

[István]

Hi all,
I'm a novice in the world of Python and to begin with something useful I 
want to create a small tool for my microcontroller work. So I wrote a 
binary file compare (called bfc). It is just a few lines and put here 
with two sample files: http://www.evoran.hu/tmp
I have found a keypress handler and built into my program. It works fine 
as long as I hit keys normally, but gives extra characterts if I keep 
pressing some key, e.g. up or down arrow keys. It runs on a Linux system.
What's the wrong with it?
Thanks for any help,
István