book

Object-Oriented Python

by Irv Kalb

January 2022

Beginner to intermediate

416 pages

10h 21m

English

No Starch Press

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Who Is This Book For?Python Version(s) and InstallationHow Will I Explain OOP?What’s in the BookDevelopment EnvironmentsWidgets and Example Games
Higher or Lower Card GameRepresenting the DataImplementationReusable CodeBank Account SimulationsAnalysis of Required Operations and DataImplementation 1—Single Account Without FunctionsImplementation 2—Single Account with FunctionsImplementation 3—Two AccountsImplementation 4—Multiple Accounts Using ListsImplementation 5—List of Account DictionariesCommon Problems with Procedural ImplementationObject-Oriented Solution—First Look at a ClassSummary
Building Software Models of Physical ObjectsState and Behavior: Light Switch ExampleClasses, Objects, and InstantiationWriting a Class in Python Scope and Instance VariablesDifferences Between Functions and MethodsCreating an Object from a ClassCalling Methods of an ObjectCreating Multiple Instances from the Same ClassPython Data Types Are Implemented as ClassesDefinition of an ObjectBuilding a Slightly More Complicated ClassRepresenting a More Complicated Physical Object as a ClassPassing Arguments to a MethodMultiple InstancesInitialization ParametersClasses in UseOOP as a SolutionSummary
Revisiting the DimmerSwitch ClassHigh-Level Mental Model #1A Deeper Mental Model #2What Is the Meaning of “self”?Summary

Bank Account ClassImporting Class CodeCreating Some Test CodeCreating Multiple AccountsMultiple Account Objects in a ListMultiple Objects with Unique IdentifiersBuilding an Interactive MenuCreating an Object Manager ObjectBuilding the Object Manager ObjectMain Code That Creates an Object Manager ObjectBetter Error Handling with Exceptionstry and exceptThe raise Statement and Custom ExceptionsUsing Exceptions in Our Bank ProgramAccount Class with ExceptionsOptimized Bank Class Main Code That Handles ExceptionsCalling the Same Method on a List of ObjectsInterface vs. ImplementationSummary
Installing PygameWindow DetailsThe Window Coordinate SystemPixel ColorsEvent-Driven ProgramsUsing PygameBringing Up a Blank WindowDrawing an Image Detecting a Mouse ClickHandling the KeyboardCreating a Location-Based AnimationUsing Pygame rects Playing SoundsPlaying Sound EffectsPlaying Background MusicDrawing Shapes Reference for Primitive Shapes Summary
Building the Screensaver Ball with OOP Pygame Creating a Ball ClassUsing the Ball ClassCreating Many Ball ObjectsCreating Many, Many Ball ObjectsBuilding a Reusable Object-Oriented ButtonBuilding a Button Class Main Code Using a SimpleButtonCreating a Program with Multiple ButtonsBuilding a Reusable Object-Oriented Text DisplaySteps to Display Text Creating a SimpleText ClassDemo Ball with SimpleText and SimpleButton Interface vs. Implementation CallbacksCreating a CallbackUsing a Callback with SimpleButtonSummary
Passing Arguments into a Function or MethodPositional and Keyword ParametersAdditional Notes on Keyword ParametersUsing None as a Default ValueChoosing Keywords and Default ValuesDefault Values in GUI WidgetsThe pygwidgets PackageSetting UpOverall Design ApproachAdding an ImageAdding Buttons, Checkboxes, and Radio ButtonsText Output and InputOther pygwidgets Classespygwidgets Example ProgramThe Importance of a Consistent APISummary
Encapsulation with FunctionsEncapsulation with ObjectsObjects Own Their DataInterpretations of EncapsulationDirect Access and Why You Should Avoid ItStrict Interpretation with Getters and SettersSafe Direct AccessMaking Instance Variables More PrivateImplicitly PrivateMore Explicitly PrivateDecorators and @propertyEncapsulation in pygwidgets ClassesA Story from the Real WorldAbstractionSummary
Sending Messages to Real-World ObjectsA Classic Example of Polymorphism in ProgrammingExample Using Pygame ShapesThe Square Shape ClassThe Circle and Triangle Shape ClassesThe Main Program Creating ShapesExtending a Patternpygwidgets Exhibits PolymorphismPolymorphism for OperatorsMagic Methods Comparison Operator Magic MethodsA Rectangle Class with Magic MethodsMain Program Using Magic MethodsMath Operator Magic MethodsVector ExampleCreating a String Representation of Values in an ObjectA Fraction Class with Magic MethodsSummary
Inheritance in Object-Oriented ProgrammingImplementing Inheritance Employee and Manager ExampleBase Class: EmployeeSubclass: ManagerTest CodeThe Client’s View of a SubclassReal-World Examples of InheritanceInputNumberDisplayMoneyExample UsageMultiple Classes Inheriting from the Same Base ClassAbstract Classes and MethodsHow pygwidgets Uses InheritanceClass HierarchyThe Difficulty of Programming with InheritanceSummary
Object LifetimeReference CountGarbage CollectionClass VariablesClass Variable ConstantsClass Variables for CountingPutting It All Together: Balloon Sample ProgramModule of ConstantsMain Program CodeBalloon ManagerBalloon Class and ObjectsManaging Memory: SlotsSummary
The Card ClassThe Deck ClassThe Higher or Lower GameMain Program Game ObjectTesting with __name__ Other Card GamesBlackjack DeckGames with Unusual Card DecksSummary
Timer Demonstration ProgramThree Approaches for Implementing TimersCounting FramesTimer EventBuilding a Timer by Calculating Elapsed TimeInstalling pyghelpers The Timer ClassDisplaying TimeCountUpTimerCountDownTimerSummary
Building Animation ClassesSimpleAnimation ClassSimpleSpriteSheetAnimation ClassMerging Two ClassesAnimation Classes in pygwidgetsAnimation ClassSpriteSheetAnimation ClassCommon Base Class: PygAnimationExample Animation ProgramSummary
The State Machine ApproachA pygame Example with a State MachineA Scene Manager for Managing Many ScenesA Demo Program Using a Scene ManagerThe Main ProgramBuilding the ScenesA Typical SceneRock, Paper, Scissors Using ScenesCommunication Between ScenesRequesting Information from a Target SceneSending Information to a Target SceneSending Information to All ScenesTesting Communications Among ScenesImplementation of the Scene Managerrun() MethodMain MethodsCommunication Between ScenesSummary
Modal Dialogs Yes/No and Alert DialogsAnswer DialogsBuilding a Full Game: DodgerGame OverviewImplementationExtensions to the GameSummary
Model View ControllerFile Display ExampleStatistical Display ExampleAdvantages of the MVC PatternWrap-Up

Content preview from Object-Oriented Python

9 Polymorphism

This chapter is about the second major tenet of OOP: polymorphism. Its component parts are from the Greek: the prefix poly means “much” or “many,” and morphism means “shape,” “form,” or “structure.”

So, polymorphism essentially means many forms. I’m not talking about a Star Trek–style shape-shifting alien—in fact, it’s quite the opposite. Rather than one thing taking on many shapes, polymorphism in OOP is about how multiple classes can have methods with the exact same names. This will eventually give us a highly intuitive way to act on a collection of objects, independent of what class each came from.

OOP programmers often ...