[ZuLuuuuuu]

> Other languages do not typically make such choices and if they do they make updating codebases relatively easy.

I want to understand what was so hard about porting code from Python 2 to 3. I ported a few tens of thousand lines of Python 2 code to Python 3 and it was pretty trivial. In my experience the only thing that made porting code hard was when a package you depended on was not ported to Python 3 yet. But maybe my experience does not reflect some other cases. Can you eloborate on what was so hard about porting code from Python 2 to 3?

[willis936]

I have a pretty nasty example here:

https://news.ycombinator.com/item?id=25890126

How do I regression test five different pieces of DAQ hardware? My best plan is to pull them working systems and deal with them missing. I don’t think it’s a good use of resources to buy extra DAQ cards just for a regression test bed.

Regardless of that, moving from python 2.5 to 2.7 is not trivial because not all used libraries were even updated to 2.7 from 2.5. Some that were broke backwards compatibility. How far do I have to bend backward just to get in the right place to update to python 3? I see many comments trivializing the effort needed to update to python 3 because they know of narrow use cases and expect large amounts of resources to maintain code. That isn’t the reality for most users.

[OakNinja]

The hardship of porting from 2 to 3 very much depends on how critical the software is. Porting 1000 lines of python 2 that deals with files encoded in various ways where it’s impossible to test all edge cases and where a failure might lead to huge liability charges is hard not because it’s hard to run 2to3 and do some random tests, but because you don’t know what you have missed. And still, a 300k lines of code project might be fine to just run 2to3 on and then find the bugs as you go. It’s a matter of context.

[wegs]

And the opposite -- tons of little unimportant scripts sitting around that add a lot of value as a whole, but just aren't worth devoting to rewriting on a whim of poor decision making skills of the Python developer team....

I have Python code dating back to when I was an undergrad. It's sad to see the Python team decide to nuke that. My C code from then (mostly) runs fine still.

The team decided to externalize a massive cost on its community without much benefit. That was sad to see at the time, and it continue to be sad to see.

[labawi]

As someone who does a decent part of development in python, I'd say you are using the wrong language, if you can't test your edge cases and have huge liabilities.

Python code is inherently almost-untestable and fragile. These days, when coding something critical and non-trivial, I choose a memory-safe language with static typing and type inference, ADTs, pattern matching and try to write simple yet pure functional code with well defined semantics, that works almost by definition.

[carapace]

Sure, but how does that help? I mean, absent a time machine, you're technically correct but operationally moot.

[labawi]

If you have a liability situation, maybe you could work to rectify it, instead of blaming 2to3 transition that's shaking up your house of cards?

[carapace]

> If you have a liability situation, maybe you could work to rectify it

Well yes, sure, of course.

And like you said, maybe Python isn't the right language in the first place for mission-critical life-is-on-the-line software.

But if you have already gotten yourself into a position where some piece of your business infrastructure is dependent on an obscure bit of hard-to-port-to-Python-3-and-maintain-exact-behaviour Python code, then it is exactly the "2to3 transition that's shaking up your house of cards", no?

And, furthermore, like you said, if you find yourself in this position, you should be looking at some other language entirely rather than porting to Py3, eh?

[labawi]

Note that I am not against using python in mission-critical code.

I was referring to untestable code with a myriad of edge-cases, in which case you have a problem that will surface sooner or later, be it 2to3 transition or something else.

If the code is truly static, you can ignore the transition and deprecation. Otherwise you should probably work on documentation/testing/refactoring and/or porting to another language.

2to3 transition was handled badly, up to about 2.7 and 3.4 or so, but the pains described here seem mostly self-inflicted, and I don't see it as an argument against the needed changes.

[Blikkentrekker]

These are exactly the concerns of serious enterprises that the Python developers have missed, that made them seem as though they be hobbyists that have never dealt software that actually powers infrastructure.

[paulryanrogers]

Python was intended for education originally. It's possible that some uses are just too far outside that wheelhouse to expect it to work well forever. Doubtful I'll ever write desktop GUIs in PHP for example, though it appears some have already done it.

[Blikkentrekker]

The standard library of 2 already came with many facilities that go well beyond that.

They targeted business; it came to be adopted by business; and then they were surprised that business was not enthusiastic about updating currently working code with all the potential regressions and downtime that might come from it.

[eesmith]

Could you explain how "Python was intended for education originally."?

As I recall, Python was designed for the Amoeba operating system, and drew on experience from implementing ABC; ABC was definitely designed for education.

But ABC != Python. Checking now, the first Usenet post for Python 0.9 says:

> Python can be used instead of shell, Awk or Perl scripts, to write prototypes of real applications, or as an extension language of large systems, you name it.

See https://groups.google.com/g/comp.sys.sgi/c/7r8kVgQ84j0 .

It doesn't specifically mention using Python for education.

[ZuLuuuuuu]

There are certainly some cases where even the smallest backward incompatible change would cause serious problems on some systems. Thanks for giving an example, instead of just downvoting.

[lmm]

The problem was that you could only port once all the libraries you use had ported, but libraries didn't want to commit to abandoning Python 2 quickly.

[ZuLuuuuuu]

Agreed, that was also my experience as well, the hardest part was not changing our codebase but if we depended on a package that was not ported to Python 3 yet.