The python language developers absolutely did do it wrong. You could not run mixed python2 and python3 code. Either all your dependencies were migrated and you could flip the switch and try things out, or some stragglers kept you running code with compatibilities for 2 and 3 while you waited.

And if one of your dependencies started using new features from 3.x it would break everyone stuck on 2.7, so you can't even use the new features in your library. So why would you bother migrating? So everyone was stuck in a game theoretical position where there was no first mover advantage because one straggler would invalidate all the investment.

> So everyone was stuck in a game theoretical position where there was no first mover advantage because one straggler would invalidate all the investment.

Clearly not, as most libraries are now Python 3 only, so the switch did happen.

I do see a lot of people complaining but I see no practical solutions being suggested. "Just don't do a breaking change" isn't a practical solution when the problem being fixed was such a core feature of every language, strings.

>Clearly not, as most libraries are now Python 3 only, so the switch did happen.

You don't build a convincing argument that the python developers did nothing wrong when saying this 1.5 years after python 2.7 has been EOL.

>I do see a lot of people complaining but I see no practical solutions being suggested. "Just don't do a breaking change" isn't a practical solution when the problem being fixed was such a core feature of every language, strings.

A system should have been put in place to allow python3 code to import python2 code. Then people have an incentive to actually run python3 and use python3 features.

More people are stuck on Java8 which has been EOL for a very long time. They are often stuck because Android hasn't upgraded afaik. But Java11, 14, etc can use almost all Java8 code unless it uses I think sun.misc.Unsafe or something like that. The point is that people can use modern Javas with Java libraries targeting older versions.

> The community of python users, which include companies with ten year old unmaintained scripts, did not want it invest to transition until the absolute last second.

Try shipping python3 scripts to systems that only have python2 interpreters. Doesn't work very well unless you also start to ship the interpreter and all its dependencies. I learned my lesson and just avoid distributing any Python code to customers now.

What language lets you ship scripts that use features of version X and also works on versions <X?

Docker tends to be the easy solution for all this stuff, and it's language agnostic.

> Doesn't work very well unless you also start to ship the interpreter and all its dependencies.

That basically applies to everything that isn't a statically linked binary.

Agree with you here. If you try to deploy a C program to ancient centos then it can also fail with glibc being incompatible.

https://developers.redhat.com/blog/2019/08/01/how-the-gnu-c-...

Much different from Python, though. As long as you compile your C program against the same version of libc you're running against, the program will still work, no matter how old the code. You just can't run a program that was compiled against an incompatible libc. A Python 2 interpreter can't run Python 3 code, and vice versa, no matter what, because the actual language changed.

You can't always easily compile an old C program against the new C libraries you are running. Even if you can compile it, changes in libraries can break programs. E.g. say in the ancient library, memcpy with null pointer parameters worked, if the size was zero. The new library checks it and aborts. There are all sorts of issues like this.

Every time libraries and compilers advance, you're effectively porting all the existing code. You have to fix any build breakage, and re-validate everything.

Moreover, Python is a C program. Just get the old Python 2 C code and compile it against "the same version of libc you're running" and it will work, right? Where is the problem?

Why recompile it when the existing binary still works with the current runtime? At least on Linux the old version of memcpy will still be included in the runtime library to avoid this kind of issue.

The point is that the code needs the runtime.

But it will run on a modern system if you compiled it against the CentOS version. I have a VM running to do just that. Trying to run Python 2 code on a modern runtime on the other hand will have the Python community feed your remains to the pigs.

> What language lets you ship scripts that use features of version X and also works on versions <X?

I didn't care about Python 3 features, but you can't run Python 2 code on a Python 3 interpreter either and the Python 2 interpreter was abandoned. Meanwhile you can run ancient JavaScript code on both old and modern systems, ancient C++ on both old and modern systems, ancient Java mostly on both old and modern systems, etc. .

> Docker tends to be the easy solution for all this stuff, and it's language agnostic.

I think I will rather go with statically linked binaries before I dump docker on unsuspecting users. Just the pain of getting that dependency whitelisted by their corporate IT makes my skin crawl.