Use:
import os, signal
# Pause the process
os.kill(pid, signal.SIGSTOP)
# Continue the process
os.kill(pid, signal.SIGCONT)
# Pause a process and it's children
os.killpg(pid, signal.SIGSTOP)
# Continue a process and it's children
os.killpg(pid, signal.SIGCONT)
Hope this helps someone!