Q:

How to get class inheritence working in Python?

I am supposed to create a class called Dog(Animal) which is  inheriting from Class Animal. However after I run this code, I got errors that I do not understand:
The problem is solved, no further questions that I see at the moment
class Animal:
__name = ""
__height = 0
__weight = 0
__sound = 0

def __init__(self, name, height, weight, sound):
    self.__name = name
    self.__height = height
    self.__weight = weight
    self.__sound = sound

#def set_name(self, name):
    #self.__name = name

def get_name(self):
    return self.__name

def get_height(self):
    return str(self.__height)

def get_weight(self):
    return str(self.__weight)

def get_sound(self):
    return self.__sound

def get_type(self):
    print("Animal")

def toString(self):
    return "{} is {} cm tall and {} kilograms and says{}".format(self.__name,
                                                                 self.__height,
                                                                 self.__weight,
                                                                 self.__sound)

cat = Animal('pussy', 33, 10, 'meow')
print(cat.toString())
print(cat.get_type())
print(cat.get_sound())

class Dog(Animal):
__owner = ""

def __init__(self, name, height, weight, sound, owner):
    self.__owner = owner
    super(Dog, self).__init__(name, height, weight, sound)

def set_owner(self, owner):
    self.__owner = owner

def get_owner(self):
    return self.__owner

def get_type(self):
    print("Dog") # Dog object

def toString(self):
    return "{} is {} cm tall and {} kilograms and says{} its owner is {}".format(self.__name,
                                                                                 self.__height,
                                                                                 self.__weight,
                                                                                 self.__sound,
                                                                                 self.__owner)

spot = Dog("kaili", 22, 33, "woof", "Jiahui") 
print(spot.toString())  

A:

After I added metaclass = type at the beginning, the problem is solved. I am not quite sure but seems the metaclass allows python2.7 to access python3's library. 

