Encapsulation and Polymorphism

Encapsulation restricts direct access to some of an object's components, often using private variables.

class Account:
  def __init__(self):
    self.__balance = 0  # private variable

  def deposit(self, amount):
    self.__balance += amount

  def get_balance(self):
    return self.__balance

Polymorphism allows different classes to be treated through a common interface.

class Cat:
  def sound(self):
    print("Meow")

class Dog:
  def sound(self):
    print("Bark")

def make_sound(animal):
  animal.sound()

make_sound(Cat())  # Meow
make_sound(Dog())  # Bark