A FOSS library and toolkit written in python for building a MUD, MUX, MUSH, or MUCK. Games are implemented as regular Python modules. telnet in or use the built-in webapp. Comes with a demo. Designed to let you worry about the bits that you really care about, and the framework gets out of your way. Everything from objects to players are implemented as OOP classes. Examine the parser in more detail?
Github repo: https://github.com/evennia/evennia