Summary
This chapter explains how to use abstract base classes to define blueprints that specify required methods for subclasses, enforcing consistent interfaces and enabling polymorphism and code reuse.

General domain of usage
Payment processing

**Abstract Base Classes (ABCs)** are a powerful tool in Python for designing **flexible and robust object-oriented systems**. They help create **maintainable code** by defining clear **contracts** that subclasses must follow.

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`PaymentMethod` is an **abstract base class**. It defines a required method, `pay`, that every payment type must implement. `CreditCard` and `PayPal` are concrete subclasses. They provide their own versions of the `pay` method, but follow the same interface.

The function `process_payment` works with **any** payment method because it relies on the shared abstract contract, not on specific classes.

Note

What is the key difference between an abstract class and a concrete class?

Learn how to build clean, secure, and scalable applications with Object-Oriented Programming in Python. Cover the fundamentals of classes and objects, then moves into advanced concepts such as inheritance, composition, polymorphism, and encapsulation. With clear explanations and practical examples, you'll develop the ability to design Python programs that are powerful, maintainable, and ready for real-world use.

Learn the core building blocks of object-oriented programming in Python. This section covers classes, objects, methods, and variables, giving you a solid base to understand how OOP organizes and structures code.

Abstract Classes and Blueprints