Proccess termination

[alexrait1]

I use popen.popen2 or popen.popen3 to start a new process and read from
it's stdout/ write to it's stdin.
But I need a way to know when a process terminates. If it closes it's
stdin/stdout, it doesn't mean it has really terminated...
And if possible, I would like to see an exception thrown when that
happens..
Do you know about a library that provides these tools other then the
standard os module... or should I use it otherwise?

Thanx Alex Rait.