Best way to determine if a certain PID is still running

[David Hirschfield]

I'm launching a process via an os.spawnvp(os.P_NOWAIT,...) call.
So now I have the pid of the process, and I want a way to see if that 
process is complete.

I don't want to block on os.waitpid(), I just want a quick way to see if 
the process I started is finished. I could popen("ps -p %d" % pid) and 
see whether it's there anymore...but since pids get reused, there's the 
chance (however remote) that I'd get a false positive, plus I don't 
really like the idea of calling something non-pure-python to find out.

So, should I run a monitor thread which just calls os.waitpid() and when 
the thread indicates via an event that the process completed, I'm golden?

All suggestions welcome, looking for simple and clean over wickedly-clever,
-David

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mediocre nebula.