How do I take the output of one program and use it as the input of another?

Question

I've looked at this and it wasn't much help.

I have a Ruby program that puts a question to the cmd line and I would like to write a Python program that can return an answer. Does anyone know of any links or in general how I might go about doing this?

Thanks for your help.

EDIT
Thanks to the guys that mentioned piping. I haven't used it too much and was glad it was brought up since it forced me too look in to it more.

Answer 1

p = subprocess.Popen(['ruby', 'ruby_program.rb'], stdin=subprocess.PIPE, 
                                          stdout=subprocess.PIPE)
ruby_question = p.stdout.readline()
answer = calculate_answer(ruby_question)
p.stdin.write(answer)
print p.communicate()[0]  # prints further info ruby may show.

The last 2 lines could be made into one:

print p.communicate(answer)[0]