如何使用返回的值在Python中打开类的另一个实例？

Question

I am on exercise 43 doing some self-directed work in Learn Python The Hard Way . And I have designed the framework of a game spread out over two python files. The point of the exercise is that each "room" in the game has a different class. I have tried a number of things, but I cannot figure out how to use the returned value from their initial choice to advance the user to the proper "room", which is contained within a class. Any hints or help would be greatly appreciated.

Apologies for the poor code, I'm just starting out in python, but at my wit's end on this.

Here is the ex43_engine.py code which I run to start the game.

---

from ex43_map import *
import ex43_map
import inspect

#Not sure if this part is neccessary, generated list of all the classes (rooms) I imported from ex43_map.py, as I thought they might be needed to form a "map"
class_list = []
for name, obj in inspect.getmembers(ex43_map):
    if inspect.isclass(obj):
        class_list.append(name)

class Engine(object):

    def __init__(self, room):
        self.room = room 


    def play(self):
        # starts the process, this might need to go inside the loop below
        next = self.room      
        start.transportation_choice()

        while True:
            print "\n-------------"
            # I have tried numerous things here to make it work...nothing has

start = StartRoom()
car = CarRoom()
bus = BusRoom()
train = TrainRoom()
airplane = AirplaneRoom()
terminal = TerminalRoom()

a_game = Engine("transportation_choice")
a_game.play()

---

And here is the ex43_map.py code

---

from sys import exit
from random import randint

class StartRoom(object):
    def __init__(self):
        pass
    def transportation_choice(self):
        print "\nIt's 6 pm and you have just found out that you need to get to Chicago by tomorrow morning for a meeting"
        print "How will you choose to get there?\n"
        print "Choices: car, bus, train, airplane"
        choice = raw_input("> ")

        if choice == "car":
            return 'CarRoom'

        elif choice == "bus":
            return 'BusRoom'

        elif choice == "train":
            return 'TrainRoom'

        elif choice == "airplane":
            return 'AirplaneRoom'

        else:
            print "Sorry but '%s' wasn't a choice." % choice
            return 'StartRoom'


class CarRoom(object):

    def __init__(self):
        print "Welcome to the CarRoom"

class BusRoom(object):

    def __init__(self):
        print "Welcome to the BusRoom"

class TrainRoom(object):

    def __init__(self):
        print "Welcome to the TrainRoom" 

class AirplaneRoom(object):

    def __init__(self):
        print "Welcome to the AirplaneRoom"

class TerminalRoom(object):

    def __init__(self):
        self.quips = [
            "Oh so sorry you died, you are pretty bad at this.",
            "Too bad, you're dead buddy.",
            "The end is here.",
            "No more playing for you, you're dead."
            ]

    def death(self):
             print self.quips[randint(0, len(self.quips)-1)] # randomly selects one of the quips from 0 to # of items in the list and prints it 
             exit(1)  

---

Answer 1

Instead of returning a string try returning an object, ie

    if choice == "car":
        return CarRoom()

Answer 2

1. It might be a good idea to make a Room class, and derive your other rooms from it.

2. The Room base class can then have a class variable which automatically keeps track of all instantiated rooms.

I haven't thoroughly tested the following, but hopefully it will give you some ideas:

# getters.py
try:
    getStr = raw_input   # Python 2.x
except NameError:
    getStr = input       # Python 3.x
getStr.type = str

def typeGetter(dataType):
    def getter(msg):
        while True:
            try:
                return dataType(getStr(msg))
            except ValueError:
                pass
    getter.type = dataType
    return getter

getInt   = typeGetter(int)
getFloat = typeGetter(float)
getBool  = typeGetter(bool)

def getOneOf(*args, **kwargs):
    """Get input until it matches an item in args, then return the item

    @param *args: items to match against
    @param getter: function, input-getter of desired type (defaults to getStr)
    @param prompt: string, input prompt (defaults to '> ')

    Type of items should match type of getter
    """
    argSet = set(args)
    getter = kwargs.get('getter', getStr)
    prompt = kwargs.get('prompt', '> ')

    print('[{0}]'.format(', '.join(args)))
    while True:
        res = getter(prompt)
        if res in argset:
            return res

.

# ex43_rooms.py
import textwrap
import random
import getters

class Room(object):
    # list of instantiated rooms by name
    ROOMS = {}

    @classmethod
    def getroom(cls, name):
        """Return room instance
        If named room does not exist, throws KeyError
        """
        return cls.ROOMS[name]

    def __init__(self, name):
        super(Room,self).__init__()
        self.name = name
        Room.ROOMS[name] = self

    def run(self):
        """Enter the room - what happens?
        Abstract base method (subclasses must override)
        @retval Room instance to continue or None to quit
        """
        raise NotImplementedError()

    def __str__(self):
        return self.name

    def __repr__(self):
        return '{0}({1})'.format(self.__class__.__name__, self.name)

class StartRoom(Room):
    def __init__(self, name):
        super(StartRoom,self).__init__(name)

    def run(self):
        print textwrap.dedent("""
            It's 6 pm and you have just found out that you need to get to Chicago
            by tomorrow morning for a meeting! How will you get there?
        """)
        inp = getters.getOneOf('car','bus','train','airplane')
        return Room.getroom(inp)

class CarRoom(Room):
    def __init__(self,name):
        super(CarRoom,self).__init__(name)

class BusRoom(Room):
    def __init__(self,name):
        super(BusRoom,self).__init__(name)

class TrainRoom(Room):
    def __init__(self,name):
        super(TrainRoom,self).__init__(name)

class PlaneRoom(Room):
    def __init__(self,name):
        super(PlaneRoom,self).__init__(name)

class TerminalRoom(Room):
    def __init__(self,name):
        super(TerminalRoom,self).__init__(name)

    def run(self):
        print(random.choice((
            "Oh so sorry you died, you are pretty bad at this.",
            "Too bad, you're dead buddy.",
            "The end is here.",
            "No more playing for you, you're dead."
        )))
        return None

# create rooms (which registers them with Room)
StartRoom('start')
CarRoom('car')
BusRoom('bus')
TrainRoom('train')
PlaneRoom('airplane')
TerminalRoom('terminal')

.

# ex43.py
from ex43_rooms import Room

def main():
    here = Room.getroom('start')
    while here:
        here = here.run()

if __name__=="__main__":
    main()