gistfile1.txt

init python:
  class ConditionSub(object):
       def __init__(self, *args):
            self.items = [ (cond, value) for cond, value in zip(args[::2], args[1::2]) ]

       def __unicode__(self):
            for cond, value in self.items:
                 if eval(cond):
                      return self.value

default is_cat = True                   
define pet = ConditionSub("is_cat", "cat", "True", "dog")

label start:
    "I have a [pet]."