classvars.rb

class Animal
  @@noise = nil

  def speak
    @@noise
  end
end

class Dog < Animal
  @@noise = 'Woof'
end

class Cat < Animal
  @@noise = 'Meeeeoowww'
end

# > load 'classvars.rb'
# => true 
# > Cat.new.speak
# => "Meeeeoowww" 
# > Dog.new.speak
# => "Meeeeoowww"

heh.

>>> class Animal:
...   noise = None
... 
>>> class Dog(Animal):
...   noise = 'Woof'
... 
>>> class Cat(Animal):
...   noise = 'meow'
... 
>>> 
>>> 
>>> print Cat.noise
meow
>>> print Dog.noise
Woof
>>> 
>>> print Cat().noise
meow
>>> print Dog().noise
Woof