Resource limits on Windows?
AFAIK, there is no portable way of getting information about the amount of processor time used by a child process in Python. But what subprocess module does (assuming you're starting the child with subprocess.Popen, which is recommended) give you is the process ID of the child process in Popen.pid. What you could do on Windows is run tasklist (see manual) using subprocess.check_output repeatedly and extract the info about the child proces from its output, using the PID as a filter.
As soon as the child process has has enough CPU time and if you used subprocess.Popen() to start the child process, you could use the Popen.kill method to kill it.
But I think it would be easier to kill the child process after after a specified number of seconds of wall time using a timer. Because if the child process hangs without using CPU time (for whatever reason), so does your python program that is waiting for it to consume CPU time.