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Introduction to Object-Oriented Programming

In programming, most languages offer various features that give us different ways to tackle technical problems. With so many different languages out there, with their own unique set of features, it became necessary to create a classification system to help distinguish those sets of features. This ultimately led to the creation of the term programming paradigm - a way to classify different programming languages and the unique features that they offered.

As we explore Python deeper, our code might fall into multiple paradigm categories at once. This is because most modern-day languages offer more than one specific paradigm we can program in. While we could spend all day exploring all the paradigms Python offers, we will instead dive into one of the most popular paradigms, and one we have already been using (maybe unknowingly), called Object-Oriented Programming (OOP).

At the forefront of any language classified as an OOP language, there must exist the ability to create programs around classes and objects. We have already started working with these concepts earlier as we built our own custom classes, class methods, and instance objects. To recap, let’s take a look at an example:

class Dog:
  sound = "Woof"

  def __init__(self, name, age):
    self.name = name
    self.age = age

  def bark(self):
    print(Dog.sound)

In the above example, we are representing a real-world entity (a dog) as a class with properties (name and age) and methods (bark). These features make up the core of the OOP paradigm and ultimately allow us to build more intricate programs. This however only scratches the surface of what we can accomplish. To explore the paradigm further, we will examine the four core pillars of OOP:

  • Inheritance
  • Polymorphism
  • Abstraction
  • Encapsulation

Each of these pillars will allow us to expand our skills so that we can take full advantage of the power of object-oriented programming in Python! We will begin exploring these pillars in later exercises but for now, let’s refresh ourselves on OOP fundamentals.

Instructions

  1. To start our exploration into OOP, create a class that will represent an employee of a company. In script.py:

    • Define a class called Employee
    • Define a class variable new_id and set it equal to 1

  2. Each Employee instance will need its own unique ID. Inside the Employee class:

    • Define an __init__() method
    • Inside __init__(), define self.id and set it equal to the class variable new_id
    • Lastly, increment new_id by 1

  3. Now create a function to output the instance id. Inside the Employee class:

    • Define a say_id() method
    • Inside say_id(), output the string "My id is " and then the instance id.

  4. Lastly, create 2 employees and have them give their ids. Outside of the Employee class:

    • Define the variable e1 and set it to an instance of Employee
    • Define the variable e2 and set it to an instance of Employee
    • Have both e1 and e2 output their ids