How to send HTTP response and receive HTTP request with web.py?

Question

I want to build a web service, the service use Web.py, and want support script to send response and receive request.

    app = web.application(urls, globals())

class index:

    def GET(self):
        return "Hello, world!"

    def POST(self):
        webdata = web.data()
        #use script to send response and receive request.
        return webdata 

But I can't find any idea to implement this feature, I want to known which API can be used in web.py or other lib?