book

Python Programming with Design Patterns

Name: Python Programming with Design Patterns
Author: James W. Cooper
ISBN: 9780137579921

by James W. Cooper

December 2021

Intermediate to advanced

352 pages

10h

English

Addison-Wesley Professional

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Cover Page
About This eBook
Halftitle Page
Title Page
Copyright Page
Pearson’s Commitment to Diversity, Equity, and Inclusion
Dedication Page
Contents at a Glance
Table of Contents
Preface
Book Organization

Register Your Book
Acknowledgments
About the Author
Part I: Introduction
The tkinter LibraryGitHub
1. Introduction to Objects
The Class __init__ MethodVariables Inside a ClassCollections of ClassesInheritanceDerived Classes Created with Revised MethodsMultiple InheritanceDrawing a Rectangle and a SquareVisibility of VariablesTypes in PythonSummaryPrograms on GitHub
2. Visual Programming in Python
Importing Fewer NamesCreating an Object-Oriented VersionUsing Message BoxesUsing File DialogsUnderstanding Options for the Pack Layout ManagerUsing the ttk LibrariesResponding to User InputApplying Colors in tkinterCreating Radio ButtonsCommunicating Between ClassesUsing the Grid LayoutCreating CheckbuttonsAdding Menus to WindowsUsing the LabelFrameMoving OnExamples on GitHub
3. Visual Programming of Tables of Data
Creating a ListboxUsing a ComboboxThe Treeview WidgetMoving OnExample Code on GitHub
4. What Are Design Patterns?
Defining Design PatternsThe Learning ProcessNotes on Object-Oriented ApproachesPython Design PatternsReferences
Part II: Creational Patterns
5. The Factory Pattern
How a Factory WorksSample CodeThe Two SubclassesBuilding the Simple FactoryFactory Patterns in Math ComputationPrograms on GitHubThought Questions
6. The Factory Method Pattern
The Swimmer ClassThe Event ClassesStraight SeedingOur Seeding ProgramOther FactoriesWhen to Use a Factory MethodPrograms on GitHub
7. The Abstract Factory Pattern
A GardenMaker FactoryHow the User Interface WorksConsequences of the Abstract Factory PatternThought QuestionsCode on GitHub
8. The Singleton Pattern
Throwing the ExceptionCreating an Instance of the ClassStatic Classes As Singleton PatternsFinding the Singletons in a Large ProgramOther Consequences of the Singleton PatternSample Code on GitHub
9. The Builder Pattern
An Investment TrackerCalling the BuildersDisplaying the Selected SecuritiesConsequences of the Builder PatternThought QuestionsSample Code on GitHub
10. The Prototype Pattern
Cloning in PythonUsing the PrototypeConsequences of the Prototype PatternSample Code on GitHub
11. Summary of Creational Patterns
Part III: Structural Patterns
12. The Adapter Pattern
Moving Data Between ListsMaking an AdapterPrograms on GitHub
13. The Bridge Pattern
Creating the User InterfaceExtending the BridgeConsequences of the Bridge PatternPrograms on GitHub
14. The Composite Pattern
An Implementation of a CompositeSalary ComputationThe Employee ClassesBuilding the Employee TreePrinting the Employee TreeCreating a Treeview of the CompositeUsing Doubly Linked ListsConsequences of the Composite PatternA Simple CompositeOther Implementation IssuesPrograms on GitHub
15. The Decorator Pattern
Decorating a ButtonUsing a DecoratorUsing Nonvisual DecoratorsThe dataclass DecoratorUsing dataclass with Default ValuesDecorators, Adapters, and CompositesConsequences of the Decorator PatternPrograms on GitHub
16. The Façade Pattern
Building the Façade ClassesCreating Databases and TablesUsing the SQLite VersionConsequences of the FaçadePrograms on GitHubNotes on MySQLUsing SQLiteReferences
17. The Flyweight Pattern
What Are Flyweights?Example CodeCopy-on-Write ObjectsProgram on GitHub
18. The Proxy Pattern
Using the Pillow Image LibraryDisplaying an Image Using PILUsing Threads to Handle Image LoadingLogging from ThreadsCopy-on-WriteComparing Related PatternsPrograms on GitHub
19. Summary of Structural Patterns
Part IV: Behavioral Patterns
20. Chain of Responsibility Pattern
When to Use the ChainSample CodeThe ListboxesProgramming a Help SystemReceiving the Help CommandThe First CaseA Chain or a Tree?Kinds of RequestsConsequences of the Chain of ResponsibilityPrograms on GitHub
21. The Command Pattern
When to Use the Command PatternCommand ObjectsA Keyboard ExampleCalling the Command ObjectsBuilding Command ObjectsThe Command PatternConsequences of the Command PatternProviding the Undo FunctionSummaryReferencesPrograms on GitHub
22. The Interpreter Pattern
When to Use an InterpreterWhere the Pattern Can Be HelpfulA Simple Report ExampleInterpreting the LanguageHow Parsing WorksThe Console InterfaceThe User InterfaceConsequences of the Interpreter PatternPrograms on GitHub
23. The Iterator Pattern
Why We Use IteratorsIterators in PythonA Fibonacci IteratorFiltered IteratorsThe Iterator GeneratorA Fibonacci IteratorGenerators in ClassesConsequences of the Iterator PatternPrograms on GitHub
24. The Mediator Pattern
An Example SystemInteractions Between ControlsSample CodeMediators and Command ObjectsConsequences of the Mediator PatternSingle Interface MediatorsPrograms on GitHub
25. The Memento Pattern
When to Use a MementoSample CodeConsequences of the Memento PatternProgram on GitHub
26. The Observer Pattern
Example Program for Watching Colors ChangeThe Message to the MediaConsequences of the Observer PatternPrograms on GitHub
27. The State Pattern
Sample CodeSwitching Between StatesHow the Mediator Interacts with the StateManagerConsequences of the State PatternState TransitionsProgram on GitHub
28. The Strategy Pattern
Why We Use the Strategy PatternSample CodeThe ContextThe Program CommandsThe Line and Bar Graph StrategiesConsequences of the Strategy PatternPrograms on GitHub
29. The Template Pattern
Why We Use Template patternsKinds of Methods in a Template ClassSample CodeThe Triangle Drawing ProgramTemplates and CallbacksSummary and ConsequencesExample Code on GitHub
30. The Visitor Pattern
When to Use the Visitor PatternWorking with the Visitor PatternSample CodeVisiting Several ClassesBosses Are Employees, TooDouble DispatchingTraversing a Series of ClassesConsequences of the Visitor PatternExample Code on GitHub
Part V: A Brief Introduction to Python
31. Variables and Syntax in Python
Data TypesNumeric ConstantsStringsCharacter ConstantsVariablesComplex NumbersInteger DivisionMultiple Equal Signs for InitializationA Simple Python ProgramCompiling and Running This ProgramArithmetic OperatorsCombined Arithmetic and Assignment StatementsComparison OperatorsThe input StatementPEP 8 StandardsString MethodsExamples on GitHub
32. Making Decisions in Python
elif is “else if”Combining ConditionsThe Most Common MistakeLooping Statements in PythonUsing break and continuePython Line LengthThe print FunctionFormatting NumbersFormatting DatesUsing the Python match FunctionReferenceMoving OnSample Code on GitHub
33. Development Environments
IDLEThonnyPyCharmVisual StudioOther Development EnvironmentsCommand-Line ExecutionCPython, IPython, and Jython
34. Python Collections and Files
SlicingSlicing StringsChanging List ContentsCopying a ListReading FilesHandling ExceptionsUsing DictionariesUsing TuplesUsing SetsUsing the map FunctionWriting a Complete ProgramUsing List ComprehensionSample Programs on GitHub
35. Functions
Returning a TupleWhere Does the Program Start?SummaryPrograms on GitHub
Appendix A: Running Python Programs
If You Have Python InstalledCreating an Executable Python ProgramCommand-Line Arguments
Index
Code Snippets

Content preview from Python Programming with Design Patterns

18 The Proxy Pattern

The Proxy pattern is used when you need to represent an object that is complex or time consuming to create by a simpler one. If creating an object is expensive in time or computer resources, a proxy enables you to postpone this creation until you need the actual object. A proxy usually has the same methods as the object it represents; when the object is loaded, it passes on the method calls from the proxy to the actual object.

There are several cases where a Proxy can be useful:

If an object, such as a large image, takes a long time to load.
If the object is on a remote machine and loading it over the network might be slow, especially during peak network load periods.
If the object has limited access rights. The proxy then ...

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Python Programming with Design Patterns

by James W. Cooper

18

The Proxy Pattern

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