Source: 📖 Problem Solving with Algorithms and Data Structures using Python 1.13.2
Date: 2021-10-27
An IS-A relationship is when classes follow a hereditary structure. For example, if class A is subclassed by class AChild, then we can say that class AChild IS-A subclass of class A.
A HAS-A relationship is when a class uses another class, but it does not reside within that class' hierarchy. Suppose that class B 'holds' an instance of class A as a property value, then we would say that class B HAS-A class A instance.