Chris, I googled for {xlib caps led} and the first link was to a forum post: http://forums.whirlpool.net.au/forum-replies-archive.cfm/619126.html
The third post down, the guy made a program to set the LED of his scroll lock key. The C source is at http://members.optusnet.com.au/foonly/hddled.c If you can manage to convert his code into python w/python-xlib you will be set. When you do, e-mail me the snippet will you ;) - Jonathan -- http://mail.python.org/mailman/listinfo/python-list