how to kill subprocess when Python process is killed?

[mark.v.weber at gmail.com]

I am writing a Python program that launches a subprocess (using
Popen).
I am reading stdout of the subprocess, doing some filtering, and
writing to
stdout of the main process.

When I kill the main process (cntl-C) the subprocess keeps running.
How do I kill the subprocess too? The subprocess is likey to run a
long time.

Context:
I'm launching only one subprocess at a time, I'm filtering its stdout.
The user might decide to interrupt to try something else; the user
wants the process and all subprocesses to go away in response
to a cntl-C

I'm new to python; solution must be for Python 2.5 (windows) to help
me.

Any help and/or pointers appreciated.