How to close a program I execute with subprocess.Popen?

[revenant81 at hotmail.com]

I'm writing a program which has to execute a command, get its output
and show it on a treeview.
This command runs for a very long time.
I want to end the execution of the command when the user closes my
application.

Right now I'm using an object my_child of type subprocess.Popen to
execute the command, inside a thread with an infinite loop where we
constantly ask for its output.

To end the program when the user closes the application, I send a
SIGTERM to the process with pid my_child.pid using os.kill. But I also
have to send a SIGTERM to my_child.pid + 1 because my_child.pid is the
pid of /bin/sh -c which is the one which calls the command, because
when I try to run Popen with shell=False, it sends an exception and
says the file or directory doesn't exist.

Anyone knows of a better way to close the command than using a
SIGTERM? I just can't help myself thinking this is an ugly dirty hack.