Introduction to Computer Programming Chapter 9: Object Oriented Programming

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Introduction to Computer Programming Chapter 9
Object Oriented Programming

• Michael Scherger
• Department of Computer Science
• Kent State University

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Contents

• Creating objects of different classes in the same
  program
• Allow objects to communicate with each other
• Combining classes
• Inheritance
• Overriding method definitions

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Blackjack Game

• Example Blackjack Game
• Imports Cards, Games

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Sending and Receiving Messages

• Sending a Message
• When one object tells another object to perform
  some action or function

• hero Player()
• invader Alien()
• def hero.blast(self, enemy)
• enemy.die()

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Sending and Receiving Messages

• Receiving a Message
• The action of executing the receiving the message
  from the calling object and performing the
  appropriate method

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Sending and Receiving Messages

• Example Alien Blaster Program

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Combining Objects

• Objects can be combined to form other objects
  or collections of objects
• A Car Class consists of individual Tires, Engine,
  Seats,individual parts that make up the whole
• A Zoo Class has a collection of other animals
  Lions, Tigers, Bears, etc
• A FreeCheckingAccount is a type of
  CheckingAccount is a type of Account

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Combining Objects

• Creating the Card Class
• A playing card has a rank and a suit
• Constants
• Constructor initializes a single Card
• __str__ is used to print out the rank and suit as
  a two character string

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Combining Objects

• Creating the Hand Class
• The Hand class is a collection of Card objects
• Uses a list
• __str__ prints out the contents of each hand
• clear() clears the hand of cards
• add() adds a card to the list
• give() gives a card to another hand

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Combining Objects

• Using Card Objects
• Combining Card Objects Using a Hand Object
• Example Playing Cards Program

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Using Inheritance to Create New Classes

• Create new classes from old
• is_a relationship
• Single inheritance
• Multiple inheritance

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Extending a Class Through Inheritance

• Creating a Base Class
• Same base classes as before
• Inheriting from a Base Class
• A deck is a special type of hand
• It has 52 cards (populate method)
• You can deal from a deck
• You can shuffle a deck

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Extending a Class Through Inheritance

• Example Playing Cards 2.0 Program

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Altering the Behavior of Inherited Methods

• Creating a Base Class

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Altering the Behavior of Inherited Methods

• Overriding Base Class Methods

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Altering the Behavior of Inherited Methods

• Invoking Base Class Methods

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Altering the Behavior of Inherited Methods

• Using the Derived Classes

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Altering the Behavior of Inherited Methods

• Example Playing Cards 3.0 Program

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Understanding Polymorphism
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Creating Modules

• Writing Modules

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Creating Modules

• Importing Modules

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Creating Modules

• Using Imported Functions and Classes

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Creating Modules

• Example Simple Game Program
• Imports Games

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Blackjack Game (Again)

• Example Blackjack Game
• Imports Cards, Games