A simple example of using cmd to build a simple REPL within a python CLI tool.

cmd_test.py

import cmd

class CmdProcessor(cmd.Cmd):
	"""A Simple Command Processor."""

	def do_greeting(self, line):
		print "Hello World!"

	def do_EOF(self, line):
		return True
		
	def do_quit(self, line):
		return True

if __name__ == '__main__':
	CmdProcessor().cmdloop()