class Animal:
  "The base class of the whole object zoo."

  atrb_animal = 0

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

  def __str__(self):
    return self.name + " is an animal"

  def eat(self):
    print self.name + ", which is an animal, is eating."

class Mammal(Animal):
  "Mammals are animals that know how to suck milk."

  def __str__(self):
    return self.name + " is a mammal"

  def suckMilk(self):
    print self.name + ", which is a mammal, is sucking milk."

class Dog(Mammal):
  "Dogs are mammals that can bark, and bite when they eat."

  def __str__(self):
    return self.name + " is a dog"

  def bark(self):
    print self.name + " is barking rather loudly."

  def eat(self):
    print self.name + " barks when it eats."
    self.bark

def test():
  a1 = Animal("Tigrinho")
  a2 = Mammal("Oncinha")
  a3 = Dog("Mameluco")
  print a1             # 1
  print a2             # 2
  print a3             # 3
  a1.eat()             # 4
  a2.suckMilk()        # 5
  a2.eat()             # 6
  a3.bark()            # 7
  a3.suckMilk()        # 8
  a3.eat()             # 9
  a1.bark()            # 10
  a1 = a3
  a1.bark()            # 11