Migrate to Python 3 Now, There's Little Time Left
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People keep writing blog posts about how easy it is to migrate your code, and I just can't imagine that these people have any experience maintaining a Python2 codebase outside of toy projects or libraries.
At work I maintain a Python2 codebase that's been under development since 2016. It's huge, relies on now-deprecated Py2-only libraries that we can't realistically switch away from, full of Py2-specific syntax, and reliant on Py2's handling of Unicode strings. We scoped out what it would be like to upgrade it to Py3, and determined that we would basically need to rewrite large parts of it from scratch. This isn't an acceptable trade-off for the business in terms of development time and priorities.
Instead we are slowly breaking out the monolith's functionality into Py3 services, which is much more tightly-scoped (and more palatable for management). But realistically speaking we will be maintaining Py2 code for the foreseeable future, and I can't imagine we are the only company in this situation.
Upgrading a production codebase from Py2 to Py3 isn't easy, or even possible in some cases. And frankly, all these blog posts suggesting that migration is trivial are insulting.
EDIT: Just checked, looks like the first commit was in 2015. But Py3 was still an option back then :(
By contrast, some of the Perl6 code we have hanging around for various tasks has aged much better.
If so, maybe a more concerted effort needs to be made around getting those upstream projects to upgrade. If some of them are refusing/dragging their feet, maybe the core python team could even get involved to help smooth the transition for everybody.
There's things that are tricky, don't get me wrong: unicode handling can be tricky, though six.ensure_str/bytes usually allows you to defer that problem. Futurize and 2to3 do so much of the work that in my experience the majority of files can be migrated by automation, unicode warts included.
The hard stuff is when you have extension modules or weird metaprogramming stuff (there's also one particular case I had to deal with around code generation). That takes effort to migrate, but it's the long tail.
If you need to rewrite your code to enable the py3 transition, the issue isn't python, it's your coding choices, and you should rewrite your code anyway.
I... don't even know what to make of this advice. Have you ever worked for an engineering organization with more than 5 members? I can't just go to my boss and say, "I need the next six months to rewrite our whole backend". I'd get laughed out of the room.
Without a clear, business-first reason for an engineering project of that magnitude, it's not ever going to be a priority or a realistic option.
Yes.
> Without a clear, business-first reason for an engineering project of that magnitude, it's not ever going to be a priority or a realistic option.
I'm not suggesting that there is any realistic solution. I'm simply stating that the cause of your pain isn't py2 to 3, but bad development practices that existed independent of language or migration. These were going to cause you pain at some point no matter what. It just happened that py3 was the forcing function, as opposed to something else next year.
But that's not the cause of my pain. Bad code can and will be written in Py2, Py3, or any other language. The cause of my pain is that the language developers chose to abandon work on the language that we use in favor of a different language, one that is fundamentally different in some important ways. As a result, the tooling and ecosystem on which we've built our product is slowly stagnating and is getting close to being fully disfunctional.
If not py3, then something else. Specifically, the tooling ad ecosystem isn't dysfunctional, you're just unable to maintain functionality among changing requirements. "We must use py3 for our codebase" isn't particularly different from "we must now support Japanese users" or "we need a new endpoint that allows us to view data along a new axis". All 3 changes had the potential to cause you developmental pain. You just hit one prior to the others.
Oh now language devs are responsible for your lack of industry practices?
As someone who has had to migrate from Py2 to Py3, it wasn't easy. Unicode/bytes/strings was the hardest aspect of it -- because Python is dynamic, there were breakages that unit tests couldn't exhaustively test for so things broke in production and we had to scramble to fix.
Other aspects were mostly automatically handled by the 2to3 tool.
Disclaimer: I spent a lot of time converting things from python2 to python3. It's a big pain.
Pet peeve: don't break compatibility for ideological reasons. For example, the print statement didn't need to die: it could have lived on as needed side-by-side with the print() function.
The other problem is that it's not only your python version that won't see official upgrades, but most of the libraries you use won't either. But I guess if you're OK with Python 2 you're probably also OK with out of date versions of django and numpy or whatever else you use.
But basically, anybody who hasn't at least started their python 3 port by now have probably already weighed the pros and cons and decided that they're never going to do it, and yelling at them isn't doing anybody any good