Object Oriented Preparation

Overview

Object-oriented programming is a powerful way of organizing programs that you’ve already used in bits and pieces. While it’s great to use Python’s built in classes such as lists and strings, object-oriented programming really shines when you make your own classes. Today we’ll focus on the paradigm of thinking with objects and starting to make your own classes.

Basic Learning Objectives

Before class, you should be able to:

• Define classes, instances, and instance variables
• Identify the syntax to define your own class
• Create a program with multiple instances of a given class

Advanced Learning Objectives

After class, you should be able to:

• Define your own class
• Define a constructor
• Explain how instance variables and methods are used by objects

Resources

You should read the following:

• Runestone 13.1 Classes and Objects - the Basics
• Runestone 13.2 Objects Revisited
• Runestone 13.3 User Defined Classes
• Runestone 13.4 Adding Parameters to the Constructor
• Runestone 13.5 Adding Other Methods to a Class

Checks

Submit answers to the following to Moodle:

1. (Checkpoint 13.13.1) Define a class called Bike that accepts a string and a float as input, and assigns those inputs respectively to two instance variables, color and price. Assign to the variable testOne an instance of Bike whose color is “blue” and whose price is 89.99. Assign to the variable testTwo an instance of Bike whose color is “purple” and whose price is 25.0.

2. (Checkpoint 13.13.2) Create a class called AppleBasket whose constructor accepts two inputs: a string representing a color, and a number representing a quantity of apples. The constructor should initialize two instance variables: apple_color and apple_quantity. Write a class method called increase that increases the quantity by 1 each time it is invoked.