I found the same thing happening.

I had to create a thread to do what I wanted and a second for the tk 
mainloop running at a lower priority so that I could get done what I wanted 
in a reasonable amount of time.

Tom Reilly

At 07:26 PM 2/17/2003 +0900, you wrote:
>Hi ppl.
>
>I've noted that mainloop() consumes too much cpu. Did you note the same 
>thing?
>--
>Yours truly, WBR, Paul Argentoff.