Running a python program during idle time only

[los]

Hi,

I'm trying to create a program similar to that of Google's desktop that
will crawl through the hard drive and index files.  I have written the
program and as of now I just put the thread to sleep for 1 second after
indexing a couple of files.

I'm wondering if anyone knows of a way that I could make so that the
program will run at full speed only runs after the computer has been
idle for a while.  I've looked at the "nice" command but that's not
exactly what I want.

Let me know if it isn't clear what I explained above. 

Thanks