What are the main principles underlying object-oriented programming?

Principles of Object-Oriented Programming (OOP):

• Encapsulation — combining data and methods that operate on that data into a single object, hiding internal details.
• Inheritance — creating new classes based on existing ones to reuse code.
• Polymorphism — the ability of objects of different classes to respond to the same messages (methods) in different ways.
• Abstraction — highlighting only the important characteristics of an object, hiding complexity.

Example in Python:

class Animal:
    def speak(self):
        pass

class Dog(Animal):
    def speak(self):
        return "Woof"

class Cat(Animal):
    def speak(self):
        return "Meow"

animals = [Dog(), Cat()]
for animal in animals:
    print(animal.speak())  # Different implementations of the same method