OOP

• Object-oriented technology


  Models real-world objects
• Real-world objects


  • table
  • television
  • chair
• Software objects


  Can represent real-world objects and other (living or non-living) entities
• The Python programming language uses objects and classes in building programs
• Objects


  • State
  • Behavior
• Dog object


  • Name, color and breed (state)
  • Bark, jump, roll-over (behavior)
• Class


  Objects with similar characteristics can fall under one class
• Dog class


  • Bulldog
  • Poodle
  • Chihuahua
• Class


  Template or blueprint from which objects are derived
• Class


  • Attributes (state/variables)
  • Methods (behavior)
• Defining a class


  Class Classname: statements...
• Class members


  • Fields (attributes)
  • Methods (behavior)
• Class instantiation


  Creating an object out of a class
• __init__ function


  Automatically called when creating a new object, allows class to initialize object attributes
• The self parameter is a reference to the current instance of the class, and is used to access variables that belong to the class
• __ indicates a private variable in Python
• Class variables are declared at the class level, instance variables are declared in the __init__ method
• Inheritance is a mechanism that allows a class to inherit properties and behaviours from another class
• Inheritance


  Derived class (subclass/child class) inherits from base class (superclass/parent class)
• Method overriding


  Subclass provides specific implementation of a method already provided by superclass
• The version of a method that is executed is determined by the object used to invoke it, not the reference variable type