Clean Architectures in Python
Clean Architectures in Python
A practical approach to better software design
About the Book
The clean architecture is the opposite of spaghetti code, where everything is interlaced and there are no single elements that can be easily detached from the rest and replaced without the whole system collapsing. The main point of the clean architecture is to make clear "what is where and why", and this should be your first concern while you design and implement a software system, whatever architecture or development methodology you want to follow.
This book is divided into two parts.
The first part is about Test-driven Development (TDD), a programming technique that will help you more reliable and easily modifiable software. I will first guide you through a very simple example in chapter 1, demonstrating how to use TDD to approach a project, and how to properly create tests from requirements. In chapter 2 I will then discuss unit testing from a more theoretical point of view, categorising functions and their tests. Chapter 3 will introduce mocks, a powerful tool that helps to test complex scenarios.
The second part introduces the clean architecture. The first chapter discusses briefly the components and the ideas behind this software structure, while chapter 2 runs through a concrete example of clean architecture for a very simple web service. Chapter 3 discusses error management and improvements to the Python code developed in the previous chapter. Finally, chapter 4 shows how to plug different database systems to the web service created previously.
- What is a software architecture?
- Why is it called “clean” architecture?
- Why Python?
About the book
- A brief history of this book
- How this book is structured
- Typographic conventions
- Why this book comes for free
- Submitting issues or patches
- About the author
Setup a Python Project
- Virtual environments
- Python projects with Cookiecutter
Part 1 - Tools
Chapter 1 - Introduction to TDD
- A real-life example
- A simple TDD project
- Setup the project
- Step 1 - Adding two numbers
- Step 2 - Adding three numbers
- Step 3 - Adding multiple numbers
- Step 4 - Subtraction
- Step 5 - Multiplication
- Step 6 - Refactoring
- Step 7 - Division
- Step 8 - Testing exceptions
- Step 9 - A more complex set of requirements
- Recap of the TDD rules
- How many assertions?
- How to manage bugs or missing features
Chapter 2 - On unit testing
- Tests should be fast
- Tests should be idempotent
- Tests should be isolated
- External systems
- Focus on messages
- The testing grid
Chapter 3 - Mocks
- Basic concepts
- First steps
- Simple return values
- Complex return values
- Asserting calls
- A simple example
- The patching decorator
- Multiple patches
- Checking call parameters
- Patching immutable objects
- Mocks and proper TDD
- A warning
- Chapter 1 - Introduction to TDD
Part 2 - The clean architecture
Chapter 1 - Components of a clean architecture
- Layers and data flow
- Main layers
- APIs and shades of grey
Chapter 2 - A basic example
- Project overview
- Project setup
- Domain models
- Use cases
- The storage system
- A command-line interface
- HTTP API
Chapter 3 - Error management
- Basic requests and responses
- Requests and responses in a use case
- Request validation
- Responses and failures
- Error management in a use case
- Integrating external systems
- The HTTP server
- The repository
Chapter 4 - Database repositories
- A repository based on PostgreSQL
- A repository based on MongoDB
- Chapter 1 - Components of a clean architecture
Part 3 - Appendices
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