In this series, I talk about design patterns and principles and show you how you can use them to improve the quality of your code. All examples are in Python.
Curated by: ArjanCodes (99 videos)
🧱 Build software that lasts. Join the Software Design Mastery waiting list → https://arjan.codes/mastery. In this video, I refactor a Python booking system from loose dictionaries into a strict domain model using dataclasses, enums, and value objects. I show where stronger types improve maintainability, and where a simple string is still the right choice. 🔥 GitHub Repository: https://git.arjan.codes/2026/flexible. 🎓 ArjanCodes Courses: https://www.arjancodes.com/courses. 💬 Join my Discord server: https://discord.arjan.codes. ⌨️ Keyboard I’m using: https://amzn.to/49YM97v. 🔖 Chapters: 0:00 Intro 0:30 The Working Before Version 1:42 The Core Design Lesson 2:55 Step 1: Replace the Dictionary 6:04 Step 2: Split Out Domain Concepts 8:38 Step 3: Replace Magic Strings 10:18 Step 4: Add a Money Value Object 13:46 Step 5: Move Rules Near the Concept 15:19 Step 6: Clean Up the Business Function 15:36 Step 7: Validate at the Boundary 17:52 Keep One String on Purpose 19:04 Why This Improves Maintainability 19:44 The *kwargs Design Smell 20:20 Final Thoughts #arjancodes #softwaredesign #python