如何让jQuery和Python在GAE应用程序中来回发送数据

I'm a web development novice writing a Python web app using Google App Engine and for the life of me I can't figure out how to successfully pass data back and forth between my jQuery and my Python. The jQuery ajax function seems to be successfully sending the data to Python as I do get my "It worked!" alert on testing. But I can't figure out how to obtain Python's response for use in updating a selectbox--I'm not sure if the problem is in my Python, my jQuery, or both. I'm a web development novice writing a Python w