Building a Vending Machine in Python Using OOP

Introduction

I attempted to build a vending machine system in Python with a strong emphasis on object-oriented programming (OOP). I wanted to use as many objects and classes as possible — even if it meant going slower — because I knew this approach would help me understand real software structures better.

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System Overview

The program is made up of two main classes:

• VendingMachine: Handles product lists, user interactions, and money processing.
• Administrator: Adds new items and can (eventually) modify or remove products. It loads and saves data using pickle.

Example snippet

goods = {}
goods["brand"] = self.writeBrand()
goods["price"] = self.writePrice()
goods["unique_key"] = self.keyGenerator()
goods["stock"] = self.writeStock()
self.vm.goodsList.append(goods)

This method in the Administrator class adds new products dynamically.

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What I struggled with

• How to pass and update shared data: I needed both classes to work on the same product list, so I passed the VendingMachine instance to Administrator.
  → This made me understand how objects can refer to and manipulate shared states.

• Input validation: Ensuring that user inputs (like price or stock) were valid integers made me think more about user experience and edge cases.

• Unique product keys: I had to manually track and generate a unique_key for each item. Later I realized this could be automated better or managed by using a database.

• Object vs Dictionary: I originally used dictionaries to store item info. I want to refactor this into its own class, like Product, for better encapsulation.

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What I learned

• Sharing state between classes by passing object references is extremely powerful and essential in larger applications.
• Separating admin tasks from customer-facing logic made my code much cleaner.
• Using pickle taught me how data can be saved and restored across sessions.

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What I want to do next

• Create a Product class to replace dictionaries and better represent individual items.
• Implement the remaining admin functions: edit, remove, and restock products.
• Add inventory checks before dispensing items.
• Eventually build a GUI version using tkinter.

This project wasn’t finished — but it’s already taught me a lot about how real systems are structured with OOP.