How to implement a stdin, stdout wrapper?

Question

I have an interactive program that runs stdin and stdout. I need to create wrapper that will send X to it\'s stdin, check that it prints Y and then redirects wrapper\'s stdin an

Answer 1

You can overwrite the sys module's stdin and stdout

import sys
sys.stdin, sys.stdout = wrapper.stdin, wrapper.stdout

These need to be file objects opened for reading and writing respectively. The original stdin and stdout are found at

sys.stdin, sys.stdout = sys.__stdin__, sys.__stdout__