Notes on Python Classes and Object-Oriented Programming

Introduction

• Series of videos on creating and using classes in Python.
• Focus on object-oriented concepts.
• Topics to cover:
  • Creating and instantiating classes
  • Inheritance
  • Class and instance variables
  • Static methods and class methods
  • Other object-oriented topics

Why Use Classes?

• Classes allow logical grouping of data and functions.
• Facilitate reuse and buildability of code.
• Terms:
  • Attributes: Data associated with a class.
  • Methods: Functions associated with a class.

Creating Classes

1. Example: Employee Class

   • Represents employees in a company.
   • Attributes include name, email, pay, and actions.
   • Creating Class:

     class Employee:
         pass
     

     • Use pass statement to leave class empty for now.

2. Instances of a Class

   • A class is a blueprint; each employee created is an instance.
   • Example of creating instances:

     employee1 = Employee()
     employee2 = Employee()
     

   • Each instance has a unique memory location.

Instance Variables

• Unique to each instance.
• Example of manual assignment of instance variables:

  employee1.first = 'Corey'
  employee1.last = 'Schaefer'
  employee1.email = 'corey.schaefer@company.com'
  employee1.pay = 50000
  

• Better Approach: Use the __init__ method to initialize instance variables automatically.

Using the __init__ Method (Constructor)

• Define __init__ to initialize attributes:

  def __init__(self, first, last, pay):
      self.first = first
      self.last = last
      self.pay = pay
      self.email = f'{first}.{last}@company.com'
  

• Pass attributes when creating an instance:

  employee1 = Employee('Corey', 'Schaefer', 50000)
  employee2 = Employee('Test', 'User', 60000)
  

Adding Methods to a Class

• Example: Method to display the full name of an employee.

  def full_name(self):
      return f'{self.first} {self.last}'
  

• Call the method:

  print(employee1.full_name())
  

Common Mistakes

• Forgetting to include self in method definitions leads to errors:
  • Without self:

    def full_name():
        return f'{self.first} {self.last}'  # Error!
    

Calling Methods from Class vs Instance

• Calling methods on instances:

  employee1.full_name()
  

• Calling methods using class name:

  Employee.full_name(employee1)
  

• Differences in needing to pass in self when using class name.

Summary

• Learned to create simple classes and the difference between a class and an instance.
• Initialized class attributes using the __init__ method.
• Created methods for functionality.
• Upcoming video will cover class variables vs instance variables.

Engagement and Support

• Questions can be asked in the comment section.
• Like and share videos to support.
• Patreon link available for contributions.