Stop Hardcoding Everything: Use Dependency Injection

→ Check out Thesys here: https://www.thesys.dev/?utm_source=youtube&utm_medium=creators&utm_campaign=arjan In this video, I explore how Dependency Injection can make your Python code cleaner, more testable, and easier to extend, using a real-world data pipeline example. I start with a tightly coupled version and progressively refactor it using manual injection, a lightweight custom DI container, and even show how frameworks like FastAPI handle DI under the hood. Design pattern playlist: https://www.youtube.com/playlist?list=PLC0nd42SBTaNf0bVJVd9e2oBV-mcUuxS0 🔥 GitHub Repository: https://git.arjan.codes/2025/di. 🎓 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 0:57 The Problem: No DI 1:29 What Is Dependency Injection? 2:13 Refactoring with Manual DI 17:19 Going Further: A Simple DI Container 28:04 Dependency Injection in FastAPI 29:53 Use Cases for Depen