mit 6.0001 classes - define class method

bunny_class.py

# implement and call a class method
class Animal(object):
  def __init__(self, age, name = "anonymous bunny"):
    assert type(age) == int
    self.age = age
    self.name = name

  def __str__(self):
    return "Hey! Here's an Animal of age: " + str(self.age) + " years."
  
  def get_age(self):
    return self.age
  
  def set_age(self, new_age):
    self.age = new_age

  def get_name(self):
    return self.name
  
  def set_name(self, new_name):
    self.name = new_name

class Rabbit(Animal):
  # class variables
  id_num = 1 # as a class variable, this is called as Rabbit.id_num

  def __init__(self, age, parent1 = "", parent2 = ""):
    Animal.__init__(self, age)
    self.parent1 = parent1
    self.parent2 = parent2
    # assign a unique ID to track instances of Rabbit - use the class variable id_num
    self.rid = Rabbit.id_num
    Rabbit.id_num += 1
  
  def get_parent1(self):
    return str(self.parent1)
  
  def get_parent2(self):
    return str(self.parent2)

  def get_id(self):
    return str(self.rid).zfill(3)

  # define a class method: defined as "__add__", this method will be called when the "+" operator is used with instances of this class
  def __add__(self, other):
    return Rabbit(0, self, other)
  
  def __eq__(self, other):
    if self.parent1.rid == other.parent1.rid and self.parent2.rid == other.parent2.rid:
      return(self.name + " and " + other.name + "have the same parents")


  def __str__(self):
    if self.parent1.name != "" and self.parent2.name != "":
      return (self.parent1.name + " and " + self.parent2.name + " are now parents of bunny " + str(self.rid) + ", named " + self.name)
    elif self.parent1.name != "":
      return (self.parent1.name + " is now parent of bunny " + str(self.rid) + ", named " + self.name)
    elif self.parent2.name != "":
      return (self.parent2.name + " is now parent of bunny " + str(self.rid) + ", named " + self.name)
    else:
      return "There's a new bunny named " + self.name + "! Its ID is: " + str(self.rid)

def new_litter(parent1, parent2):
  '''
  create a new litter of bunnies
  '''
  bunny_names = list(input('What are the bunnies\' names? (single space between names): ').split(" "))
  for i in bunny_names:
    new_bunny = parent1 + parent2
    new_bunny.set_name(i)
    print(new_bunny)

print("It's bunny season!")
new_bunnies = []
another_litter = input('Another litter? y/n: ')
while another_litter == 'y':
  name_p1 = input('Expecting new bunnies!\nFirst parent\'s name: ')
  age_p1 = int(input('Age of first parent (months): '))
  # here, want to check if there's an instance of Rabbit with self.name == name_p1 and self.age == age_p1, in which case that instance is used as the parent and no new (adult) Rabbit instance is created
  p1 = Rabbit(age_p1)
  p1.set_name(name_p1)
  name_p2 = input('Second parent\'s name: ')
  age_p2 = int(input('Age of second parent (months): '))
  p2 = Rabbit(age_p2)
  p2.set_name(name_p2)
  new_litter(p1, p2)
  another_litter = input('Another litter? y/n: ')