profile

The Friday Loop

Ridiculous Ways to Define Functions in Python | Issue #56

Published about 1 month ago • 2 min read

Hi there,

​

We all use def to define functions in Python. But did you know there are at least 7 other ways to do it? Some of them are useful. Some are questionable. And the last one is so ridiculous, it might crash your interpreter.
​

In this week’s video, I walk through each method, explain how it works, why you should use it (or not), and what it teaches us about how Python works under the hood.
​

This was a really interesting topic to explore. I learned a lot from it and I hope you will too.

​

Happy coding!

​

Cheers,

Arjan

# News

It’s My Birthday Week! 🎉

That’s right: I’m officially getting deprecated… but still fully functional! On June 8th, I’m turning 48, and to celebrate another year under the sun, I’m giving you a special gift: 20% off all ArjanCodes courses (excluding the Professional version).

It’s the perfect performance boost for your coding skills.

To claim your 20% discount, use coupon code BIRTHDAY2025 at checkout. This offer is available until June 8th at midnight!

Debugging f-strings Is Fun

Here’s something weird I came across this week. Your str(obj) call works just fine… but plug that same object into an f-string and boom — you get a TypeError.

Turns out, f-strings don't use str() under the hood — they use format(). And in some edge cases (like with proxy objects or sandboxed environments), that subtle difference matters.

Brandon Chinn wrote a great deep dive on this exact problem. Check it out here.

It’s a great reminder that Python is usually friendly, until it’s not.

# Community

How Do You Learn Software Architecture?

This week someone asked a great question in my Discord server: “I can write code, but how do I get better at designing it?”

That kicked off a really thoughtful thread about learning architecture step by step, dealing with anxiety while coding, and figuring out how to make your code easier to change later. A few great book recommendations came up too.

If you ever feel stuck trying to structure your code or scale your skills, you’re not alone, and the Discord is a great place to talk about it.

👉 Join the community now to read the discussion and share your thoughts.

Do you enjoy my content on YouTube and would you like to dive in deeper?

🚀 Check out my online courses

My courses have helped thousands of developers take the next step in their careers. Check out these courses to help grow your skills and become a senior developer:

🔧 Need help with a complex codebase?

If your team is struggling with tech debt, unclear architecture, or cloud costs that keep creeping up, my team and I can help. We don’t just review, we get in and fix things. We’re only working with a few companies at a time to stay focused, so if it sounds like a fit:

​Unsubscribe | Send by ArjanCodes

Wolvenplein 25, Utrecht, UT 3512 CK

The Friday Loop

by ArjanCodes

Every Friday, you'll get a recap of the most important and exciting Python and coding news. The Friday Loop also keeps everyone posted on new ArjanCodes courses and any limited offers coming up.

Read more from The Friday Loop

Hey everyone, I love it when I come up with a design that uses exactly the things I thought were a sign of bad design. In this week's video I show you how to build a clean Python SDK for a REST API. The idea was simple: create a reusable base model that handles all the CRUD operations so you can just write User.find() and user.save(), without duplicating logic all over your codebase. Sounds great, right? Well, after recording the video, I realized something: not all APIs will have all CRUD...

5 days ago • 1 min read

Hey everyone, Python’s flexibility is great, but if you're working on a larger project it becomes hard to make sure not everything depends on everything else. There is a way to avoid that trap, and that's by using abstractions. Unfortunately, I often see production code with way too much coupling that can be easily improved by relying on abstractions. This week’s video shows simple abstractions using Callable, ABC, and Protocol. You’ll learn how to: Reduce unnecessary imports Decouple your...

12 days ago • 1 min read

Hey everyone, I was reviewing some of the projects I’ve worked on over the past year, and I noticed something interesting: I almost never use Python’s @dataclass anymore. Not because it’s bad. In fact, dataclasses are still a great feature of the language. But as my projects have grown more complex, especially with tools like FastAPI, Pydantic, and SQLAlchemy, I’ve found that dataclasses just… don’t fit the way I design software anymore. In my latest video, I dive into this in detail. You’ll...

19 days ago • 1 min read