JuniorTheoryCommon

What does the program print?

Python

class Dog:
    sound = "woof"


a = Dog()
b = Dog()
a.sound = "grr"
Dog.sound = "bark"
print(a.sound, b.sound)

grr bark

Expecting bark bark, as if changing the class reached every instance: a.sound = "grr" created an attribute of a itself, and it hides the class one.
Expecting b.sound to stay woof, as if each instance copied it when created: b has no sound of its own, so it reads the class attribute, now bark.

JuniorTheoryCommon

Python

class Dog:
    sound = "woof"


a = Dog()
b = Dog()
a.sound = "grr"
Dog.sound = "bark"
print(a.sound, b.sound)

grr bark

Expecting bark bark, as if changing the class reached every instance: a.sound = "grr" created an attribute of a itself, and it hides the class one.
Expecting b.sound to stay woof, as if each instance copied it when created: b has no sound of its own, so it reads the class attribute, now bark.