Introduction to Computer Programming Chapter 9 Object Oriented

Introduction to Computer Programming Chapter 9: Object Oriented Programming Michael Scherger Department of Computer Science Kent State University November 28, 2005 ICP: Chapter 9: Object Oriented Programming 1

Contents • Creating objects of different classes in the same program • Allow objects to communicate with each other • Combining classes • Inheritance • Overriding method definitions November 28, 2005 ICP: Chapter 9: Object Oriented Programming 2

Blackjack Game • Example: Blackjack Game – Imports: Cards, Games November 28, 2005 ICP: Chapter 9: Object Oriented Programming 3

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() November 28, 2005 ICP: Chapter 9: Object Oriented Programming 4

Sending and Receiving Messages • Receiving a Message – The action of executing the receiving the message from the calling object and performing the appropriate method November 28, 2005 ICP: Chapter 9: Object Oriented Programming 5

Sending and Receiving Messages • Example: Alien Blaster Program November 28, 2005 ICP: Chapter 9: Object Oriented Programming 6

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 Free. Checking. Account is a type of Account November 28, 2005 ICP: Chapter 9: Object Oriented Programming 7

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 November 28, 2005 ICP: Chapter 9: Object Oriented Programming 8

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 November 28, 2005 ICP: Chapter 9: Object Oriented Programming 9

Combining Objects • Using Card Objects • Combining Card Objects Using a Hand Object • Example: Playing Cards Program November 28, 2005 ICP: Chapter 9: Object Oriented Programming 10

Using Inheritance to Create New Classes • Create new classes from old – “is_a” relationship – Single inheritance – Multiple inheritance November 28, 2005 ICP: Chapter 9: Object Oriented Programming 11

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 November 28, 2005 ICP: Chapter 9: Object Oriented Programming 12

Extending a Class Through Inheritance • Example: Playing Cards 2. 0 Program November 28, 2005 ICP: Chapter 9: Object Oriented Programming 13

Altering the Behavior of Inherited Methods • Creating a Base Class November 28, 2005 ICP: Chapter 9: Object Oriented Programming 14

Altering the Behavior of Inherited Methods • Overriding Base Class Methods November 28, 2005 ICP: Chapter 9: Object Oriented Programming 15

Altering the Behavior of Inherited Methods • Invoking Base Class Methods November 28, 2005 ICP: Chapter 9: Object Oriented Programming 16

Altering the Behavior of Inherited Methods • Using the Derived Classes November 28, 2005 ICP: Chapter 9: Object Oriented Programming 17

Altering the Behavior of Inherited Methods • Example: Playing Cards 3. 0 Program November 28, 2005 ICP: Chapter 9: Object Oriented Programming 18

Understanding Polymorphism November 28, 2005 ICP: Chapter 9: Object Oriented Programming 19

Creating Modules • Writing Modules November 28, 2005 ICP: Chapter 9: Object Oriented Programming 20

Creating Modules • Importing Modules November 28, 2005 ICP: Chapter 9: Object Oriented Programming 21

Creating Modules • Using Imported Functions and Classes November 28, 2005 ICP: Chapter 9: Object Oriented Programming 22

Creating Modules • Example: Simple Game Program – Imports: Games November 28, 2005 ICP: Chapter 9: Object Oriented Programming 23

Blackjack Game (Again) • Example: Blackjack Game – Imports: Cards, Games November 28, 2005 ICP: Chapter 9: Object Oriented Programming 24