W63-CoinCollection Class Overview

Overview

This lecture covers the design and implementation of a CoinCollection class in Python, focusing on managing groups of Coin objects with useful methods.

CoinCollection Class Structure

• CoinCollection class models a collection of coin objects.
• The sole attribute is a list that stores coin objects (self.coins).
• The constructor initializes the coins list as empty.

Key Methods in CoinCollection

• add_coin(coin): Adds a coin object to the collection.
• __str__(): Returns a string representation of all coins in the collection for easy printing.
• remove_coin(coin_type): Removes the first coin matching the specified type; reports if not found.
• total_value(): Returns the sum of all coin values as a float.
• find_by_type(coin_type): Returns a list of all coins matching the given type.
• find_rares(): Returns a list of all coins in the collection marked as rare.
• display_all(): Prints all coins in the collection by leveraging the __str__ method.
• is_empty(): Returns True if the collection has no coins, otherwise False.

Using the CoinCollection Class

• Create a collection: my_collection = CoinCollection()
• Add coins: my_collection.add_coin(coin1)
• Remove coins by type: my_collection.remove_coin("Quarter")
• Calculate total value: my_collection.total_value()
• Find coins by type or rarity: my_collection.find_by_type("Quarter"), my_collection.find_rares()
• Display all coins: my_collection.display_all()
• Check if collection is empty: my_collection.is_empty()

Best Practices Highlighted

• Use clear, descriptive method names.
• Limit class responsibility to managing coin collections.
• Test code incrementally to catch and fix errors early.
• Leverage object-oriented design for code reusability and maintainability.

Key Terms & Definitions

• Coin — A class modeling a single coin with attributes like type, value, and rarity.
• Collection — A group or list of coin objects managed by the CoinCollection class.
• Method — A function defined in a class to operate on its data (e.g., add_coin).
• Rare — An attribute indicating if a coin is uncommon or valuable.

Action Items / Next Steps

• Review and test each method of the CoinCollection class.
• Prepare for the next lecture on implementing a menu-driven program using these classes.
• Practice writing and testing simple classes and methods in Python.