This subject builds on the knowledge and skills acquired in the Fundamentals of Programming subject by expanding on the principles and techniques that support the development and testing of Python-based applications. This necessitates competence on unit tests, the test-driven development environment, exception handling, debugging, integrated development environments and external test libraries. The application of object-oriented programming concepts and principles are therefore the primary focus of this subject, which include the design patterns and best practices associated with Python programming language.