My first CherryPy program... import cherrypy class HelloWorld(object): def index(self): stringToDisplay = "Hello world!" number = 1 stringToDisplay += "The number is {0} ".format(number) number = 14 stringToDisplay += "The number is {0} ".format(number) stringToDisplay += "" return stringToDisplay index.exposed = True cherrypy.quickstart(HelloWorld()) So, the cherrypy.quickstart line mounts an instance