I would like to port a screenshot utility program from C to Python.
So I started to experiment with Python + Xlib. The original code... is written in C and Xlib + GTK/GDK libraries. 

A simple start.
My first test code should draw a line on the root window (on the desktop surface), but it does not work. 

Can you help me.

The code is here:

See also this  message on the Ubuntuforums.org

Most kindly
  Moma Antero