Chapter 1. Principles of Software Architecture

This is a book on Python. At the same time, it is a book about software architecture and its various attributes, which are involved in a software development life cycle.

In order for you to understand and combine both aspects, which is essential to get maximum value from this book, it is important to grasp the fundamentals of software architecture, the themes and concepts related to it, and the various quality attributes of software architecture.

A number of software engineers, taking on senior roles in their organizations, often get very different interpretations of the definitions of software design and architecture, and the roles they play in building testable, maintainable, scalable, secure, and functional software.

Though there is a lot of literature in the field, which is available both in conventional book form and on the internet; very often, the practitioners among us get a confusing picture of these very important concepts. This is often due to the pressures involved in learning the technology rather than learning the fundamental design and architectural principles underlying the use of technology in building systems. This is a common practice in software development organizations, where the pressures of delivering working code often overpowers and eclipses everything else.

A book such as this one, strives to transcend the middle path in bridging the rather esoteric aspects of software development related to its architectural quality attributes to the mundane details of building software using programming languages, libraries, and frameworks—in this case, using Python and its developer ecosystem.

The role of this introductory chapter is to demystify these concepts, and explain them in very clear terms to the reader to prepare his/her for the path towards understanding the rest of this book. Hopefully, by the end of this book, the concepts and their practical details will represent a coherent body of knowledge to the reader.

We will now get started on this path without any further ado, roughly fitting this chapter into the following sections:

• Defining software architecture
• Software architecture versus design
• Aspects of software architecture
• Characteristics of software architecture
• Why is software architecture important?
• System versus Enterprise Architecture
• Architectural quality attributes
  • Modifiability
  • Testability
  • Scalability/performance
  • Security
  • Deployability