#encoding:utf-8
class Bird:
    def __init__(self):
        self.hungry=True

    def eat(self):
        if self.hungry:
            print (" aaah..")
            self.hungry=False
        else :
            print ("no ,thanks")



class SongBird(Bird):
    def __init(self):
        Bird.__init__(self)
        self.sound = "Squak!"

    def sing(self):
        print(self.sound)


if __name__=="__main__":
    sb=SongBird()
    #['_SongBird__init', '__doc__', '__init__', '__module__', 'eat', 'hungry', 'sing']
    print (dir(sb))
    sb.sing()
    sb.eat()

錯誤提示：

AttributeError: SongBird instance has no attribute 'sound'，提示沒有sound屬性