Composition vs Inheritance in Python: When Should You Use What?

In Python OOP, one of the most debated design decisions is whether to use Composition vs Inheritance to organize your codebase effectively. The two most common paradigms are inheritance and composition. While inheritance promotes reusability by extending base classes, composition encourages flexibility by building objects using other objects.

In this guide, we’ll break down what each approach offers, when to use them, and how to design clean, maintainable Python code using both techniques.

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🧱 What Is Inheritance in Python?

Inheritance allows one class (child/subclass) to acquire the attributes and behaviors of another class (parent/superclass).

✅ Key Characteristics:

• Follows an "is-a" relationship
• Enables code reuse across related classes
• Supports method overriding and extension

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🧩 What Is Composition in Python?

Composition is about building classes that use other classes’ functionality via object references rather than inheritance.

✅ Key Characteristics:

• Follows a "has-a" relationship
• Encourages loose coupling and encapsulation
• Allows reusing components in unrelated systems

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🤔 When to Use Composition Over Inheritance?

Use composition when:

• You want to reuse functionality across unrelated classes
• You want to change behavior at runtime
• You need better unit testability and modularity

Use inheritance when:

• You have a clear hierarchy or shared interface
• You need to override or extend base behavior
• You're working with frameworks that require subclassing

• You have a clear hierarchy or shared interface
• You need to override or extend base behavior
• You're working with frameworks that require subclassing

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🔍 Frequently Asked Questions

Is composition better than inheritance in Python?

It depends. Composition is generally more flexible and testable, while inheritance is more intuitive for hierarchical models. Many modern systems prefer composition for maintainability.

What is multiple inheritance?

Multiple inheritance allows a class to inherit from more than one parent class. It can be powerful but may lead to complex issues like the diamond problem. Python uses Method Resolution Order (MRO) to handle this.

How to structure classes in Python projects?

Group related behaviors using composition, follow SOLID principles, and keep classes focused on single responsibilities.

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📚 Related Guides

• Deep Dive on Inheritance vs Composition – RealPython →
• What Is Asynchronous vs Synchronous Code in Python? →
• Big O Notation in Python: What Every Developer Should Know →
• SOLID Principles in Python →
• Design Patterns in Python →

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