Code duplication
Code duplication is the presence of equivalent or substantially similar source code or implementation logic in multiple locations within a software system.
Software Design for Python Programmers
Duplicate code is the presence of multiple substantially similar copies of an implementation in a program.
- How it is used
- Diagnoses repeated implementations as a design smell during incremental object-oriented refactoring.
- How deep it goes
- Defines duplication, traces maintenance consequences across examples, and demonstrates shared implementations without fully specifying every refactoring.
- Examples
- Uses book catalogues, toy behaviors, sports reports, fundraising workflows, sports algorithms, and collection-specific player iteration.
- What you can do after
- Apply it via shared functions, cohesive classes, or design patterns that centralize common behavior and isolate variants.
Read how Software Design for Python Programmers explains code duplication →
Object-Oriented Software Design in C++
Code duplication is the presence of multiple copies of substantially similar implementation logic in a program.
- How it is used
- Uses duplication as a practical signal for finding poor design, maintenance hazards, and change leaks.
- How deep it goes
- Explains causes and consequences through several C++ examples, then points to shared functions, cohesive classes, and design patterns.
- Examples
- Illustrates duplication with book catalogues, sports reports, fundraising clients, and team reports over arrays, vectors, and maps.
- What you can do after
- Evaluate/understand repeated logic and consolidate it into shared functions, cohesive classes, or appropriate design-pattern structures.
Read how Object-Oriented Software Design in C++ explains code duplication →
Build Financial Software with Generative AI (From Scratch)
Code duplication is the repetition of substantially similar implementation logic in multiple places within a software system.
- How it is used
- Guides maintainability work while expanding ACH processing and exception views.
- How deep it goes
- Demonstrates duplicated methods and page logic, then applies extraction and component reuse without formal measurement or taxonomy.
- Examples
- Uses duplicated get_db code, ACH parsing, and a shared exceptions DataGrid component.
- What you can do after
- Apply it by extracting duplicated methods into helpers or reusable components and evaluating component data flow.
Read how Build Financial Software with Generative AI (From Scratch) explains code duplication →
Related concepts
- don't repeat yourself principleaddresses · The Don’t Repeat Yourself principle is a software design guideline that gives each piece of knowledge or behavior a single authoritative representation to avoid unnecessary duplication.
- refactoringaddressed by · Refactoring is the restructuring of existing software or code to change its internal organization and improve its design, typically while preserving externally observable behavior.
- code smellkind of · A code smell is a recognizable symptom in source code suggesting a potential design, implementation, or maintainability problem without necessarily indicating a defect.
- reusecontrasts with · Reuse is applying an existing resource, implementation, or capability again in another context rather than creating or duplicating it.
- multiple inheritanceaddressed by · Multiple inheritance is an object-oriented inheritance model in which a class or type directly derives attributes or behavior from more than one parent.
- technical debtproduces · Technical debt is the future cost, effort, or risk created by technical choices or deferred work that make a system harder to change, maintain, or operate.
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