Python, требующий преобразования атрибута в строку

from sys import exit
from random import randint

class Map(object):

 def death(): 
    print quips[randint (0, len(quips)-1)]
    exit(1)

 def princess_lives_here():
    print "You see a beautiful Princess with a shiny crown."
    print "She offers you some cake."

    eat_it = raw_input(">")

    if eat_it == "eat it":
        print "You explode like a pinata full of frogs."
        print "The Princess cackles and eats the frogs. Yum!"
        return 'death'

    elif eat_it == "do not eat it":
        print "She throws the cake at you and it cuts off your head."
        print "The last thing you see is her munching on your face. Yum!"
        return 'death'

    elif eat_it == "make her eat it":
        print "The Princess screams as you cram the cake in her mouth."
        print "Then she smiles and cries and thank you for saving her."
        print "She points to a tiny door and says, 'The Koi needs cake too.'"
        print "She gives you the very last bit of cake and shoves you in."
        return 'gold_koi_pond'

    else:
        print "The Princess looks at you confused and just points at the cake."
        return 'princess_lives_here'

class Engine(object):

 def __init__(self, start, quips):
    self.quips = [
        "You died. You suck at this.",
        "Your mom would be proud, if she were smarter",
        "Such a luser.",
        "I have a small puppy that better at this."
    ]
    self.start = start

 def play(self):
    next = self.start

    while True:
        print "\n-----"
        room = getattr(self, next)
        next = room()

m = Map()
e = Engine(m, "princess_lives_here")

e.play()

След назад я получаю в терминале:

    Traceback (most recent call last):
  File "ec42.py", line 162, in <module>
    e.play()
  File "ec42.py", line 156, in play
    room = getattr(self, next)
TypeError: getattr(): attribute name must be string

Я работаю над этим слишком долго, и просто не могу прибить его. Основная проблема заключается в том, чтобы класс карты выполнялся внутри класса движка как объект. заранее спасибо за помощь.