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Classes

We can create our own custom type (as opposed to Python's built-in types) by defining classes. Here are the slides for both videos of this lecture: pdf. The answers to the questions asked during this lecture are in a separate file at the end of this page.

Part 1: Initializing attributes

In this segment we start a simple class definition that has two parts: the specifications and the __init__ method. We define the __init__ method, which is called by the constructor in order to assign attributes (variables in an object of a class). We also talk about the class specifications--class invariant--and a way to enforce the invariant by using assert statements. We end this segment by showing you how to make arguments optional.

• video
• audio only
• Code: college_simple.py

Part 2: Class attributes and method definitions

A variable that belongs to the class and is shared by all the instances is a Class Attribute. Be careful to use to class name, not an object variable name, to access a class attribute. We show you how to define methods in the class: (1) have self as the first parameter in any method's parameter list and (2) use self to access attributes in the method body.

• video
• audio only
• Code: college.py

Answers to the 2 questions asked during lecture: pdf