关于python getattr()函数使用疑问。

Question

我在创建一个类Game 并创建一个属性start,创建一个实例后执行play()方法，使用getattr函数
获取start属性值，也就是要执行的函数名，运行提示getattr 第二个参数（属性名）必须是str类型，但是我创建实例传入的参数"testroom"就是字符串啊，只不过是赋值给变量next了

class Game(object):

    def __init__(self, start):
        self.start = start
        
    def play(self):
        next = self.start
        while True:
            print "\n----------"
            room = getattr(self, next)
            next = room()
    
    def testroom(self):
        pass
a_game = Game("testroom")
a_game.play()

这是笨办法学Python 上的第42个习题，我按书上敲的，不知道哪里出错了，求指点。

Answer 1

def play(self):
        next = self.start
        while next:  #要指定循环的跳出条件
            print "\n----------"
            room = getattr(self, next)  #第一次可以获取到
            next = room()  #因为testroom()没有返回值，这里next变空了
         
         

There is no problem when running for the first time, but after running
next = room(), because testroom() has no return value, next is assigned an empty value. If we continue, getattr(self, next) becomes getattr (self,None)

Answer 2

The first execution of getattr was successful. The second time because of next = room(), next is not a string, so...