Python Polymorphism & Dunder Methods: Complete the Coin Project | Python Tutorial #29

In this final part of our Coin System project, we master the fourth and final pillar of Object-Oriented Programming: Polymorphism!

You’ll learn how to "override" parent methods so that different objects behave differently—even when they share the same parent. For example, why does a 1p coin rust while a 5p coin stays clean? We solve that with polymorphic methods. Plus, we’ll use the `__str__` dunder method to make our objects printable and create a professional-grade data table using argument unpacking.

📌 Timestamps:
0:00:00 Introduction: Completing the Coin Project
0:01:00 Creating the Bronze Coins (1p and 2p Classes)
0:02:50 What is Polymorphism? (Multiple Forms, One Method Name)
0:03:30 Overriding Methods: Making Silver coins "rust-proof"
0:05:20 Expanding the system: 10p, 20p, and 50p Classes
0:06:55 Finishing with the £1 and £2 Coins
0:08:25 Creating a List of Coin Objects
0:09:40 Formatting a professional Data Table in the Console
0:10:50 Unpacking Arguments for clean String Formatting
0:12:00 Introducing the _str_ Dunder Method for human-readable output
0:14:30 Final Demo: Printing the complete set of UK currency
0:16:15 Summary & Preview: Next up, the Bank Account Project!

This is Episode #29 of the Complete Python 2026 series. If you've made it this far, you now understand the four pillars of OOP: Abstraction, Encapsulation, Inheritance, and Polymorphism.

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