subprocess leaves child living

[Thomas Dybdahl Ahle]

Hi, When I do a small program like

from subprocess import Popen
popen = Popen(["ping", "google.com"])
from time import sleep
sleep(100)

start it and kill it, the ping process lives on.
Is there a way to ensure that the ping process is always killed when the 
python process is?
I can't use atexit, as ping then isn't killed when python is killed "in 
the hard way"