L7: Object-Oriented Programming – Part II

Overview

This lecture extends the OOP foundation from L6 into more advanced class design. You will learn how class methods and static methods differ from instance methods, how to implement the three object relationships (association, aggregation, and composition) identified in the design phase, and how to build class hierarchies using inheritance and super(). The lecture then covers polymorphism through duck typing and method overriding, and abstract base classes as a way to enforce a consistent interface across subclasses. Three additional topics are included for your information: data classes for reducing boilerplate, __slots__ for memory-efficient attribute storage, and typing.Protocol for structural subtyping without inheritance. All examples continue with the Robotics Competition Management System running domain introduced in L6.

Learning Objectives

By the end of this lecture, you will be able to:

• Distinguish between class methods, static methods, and instance methods.

• Explain and implement association, aggregation, and composition.

• Use inheritance to create class hierarchies with super().

• Understand generalization and specialization in class design.

• Apply polymorphism through duck typing and method overriding.

• Define abstract base classes with the abc module.

• Use typing.Protocol for structural subtyping and flexible interfaces.

• Use __slots__ to restrict attributes and reduce memory overhead.

• Use @dataclass to reduce boilerplate for data-centric classes.

Next Steps

• In the next lecture, we will begin working with ROS 2:

  • What ROS 2 is and why it matters for robotics

  • Nodes, topics, messages, and the ROS 2 computation graph

  • Writing your first publisher and subscriber in Python

  • Building and running ROS 2 packages

• Review and experiment with all code snippets and exercises from today’s lecture.

• Practice building class hierarchies with abstract base classes.

• Read the ROS 2 Jazzy Beginner Tutorials.