Jacob Kaplan-Moss

Why I’m excited about Python 3

I wrote this post in 2009, more than 13 years ago. It may be very out of date, partially or totally incorrect. I may even no longer agree with this, or might approach things differently if I wrote this post today. I rarely edit posts after writing them, but if I have there'll be a note at the bottom about what I changed and why. If something in this post is actively harmful or dangerous please get in touch and I'll fix it.

This is a rough transcript, with links, of a 3-minute lightning talk I gave at LCA. It’s obviously not a complete argument; just a 180-second pitch for why the drama about Py3k is all smoke and no fire.

I’m excited about porting my code to Python 3, and you should be, too.

I’m sure all the Python users here are aware of the recent release of Python 3.0. Python 3.0 is the first Python release in something like a decade that is fundamentally incompatible with the previous release. There’s been a lot doom & gloom & naysaying about this. Some have suggested that Python 3 marks the moment where Python jumped the shark.

That’s not true, and I’m going to tell you why.

So, I’m one of the maintainers of Django. Django’s about 75 kLOC, and it won’t run under Python 3. Nor will anything I’ve written in Python to date. In my near future I see quite a bit of time porting code to Python 3 – as does every maintainer of every other Python program out there.

Now this sounds very scary. It sounds like I’m saying that every single one of the millions of lines of Python out there is going to have to be ported to a new language. You can see why this would cause a lot of angst: it seems like an impossible task.

But I’m still incredibly excited about porting to Python 3, and I’m going to give you three reasons why you should be excited, too.

First, there’s no hurry.

Python 3.0 is out today, but I don’t think anyone really expects you to switch to it immediately. Support for the Python 2 series will continue in parallel for quite some time. Many features of Python 3 will be backported into the Python 2 series, so you can make the move in baby steps.

A five-year timeline for moving to Python 3 is entirely reasonable. Python 2 isn’t going anywhere.

Second, it’s not going to be that hard.

Python 3 ships with a tool, 2to3 which will automate a great deal of the gruntwork. A great deal of code can be automatically upgraded to Python 3. Where tools won’t work, there are human resources. There’s a dedicated python-porting mailing list for help with porting code to Python 3.

If you’ve got good test coverage, porting these final bits should be easy, though not exactly fun. Run tests, fix failures, rinse, and repeat. If you don’t have good test coverage, I don’t have a lot of sympathy for you.

Finally, it’ll be worth your effort.

Python 3 has a huge set of improvements I can’t possibly enumerate. But more importantly, Python 3 is simply a better foundation from which to build the language forward. Improvements past 3.0 will come quicker and be more profound.

We all refactor code to take advantage of better APIs, or to build on improved frameworks, or to make an investment in future technology. Refactoring is part of the lifecycle of a healthy project. Moving to Python 3 is one of these refactorings. And we all know that while refactoring can be painful, the grass is indeed greener on the other side of this particular fence.

So, relax and don’t worry. Trust in Guido and your faith shall be rewarded!