There are several example usage of wexpect. Choose one as template of your application.
hello_wexpect is the simplest example. It starts a windows command interpreter (aka. cmd) lists the current directory and exits.
python is a full custom example code. This example script runs foo python program, and communicates with it. For better understanding please run natively foo.py first, which is a very basic stdio handler script.
cmd_wrapper is a simple wrapper around the cmd windows command interpreter. It waits for commands executes them in the spawned cmd, and prints the results.