I don't think the parent is talking about Python 2 -> 3. I think they are pointing out that for many developers, moving to Python 3 happened very late. That means they ran 2.7 since 2010 (roughly 10 years now.) Now that they are on 3.x, they get issues with each new 3.x release.

The argument is that being on 2.7 for so long gave a false impression of the language being more stable than it is - developers just weren't using new versions.

Well to be fair the 2020 end of life date was announced almost a decade ago. That said, I know that fortune 500 companies that used 2.7 to develop new code in 2017 -- which was a mistake -- mostly because they were tied to old version of RHEL and they were too lazy to try to get Python 3 to work on an old version of RHEL.

So 2020 rolled around and the pypi libraries they were using were no longer supported even though RHEL would support python 2.7. So yeah, it was a really bad experience for everyone involved.

Some people are still using 2.7 in production.

Maybe there will be a company like Red Hat that announces to support python 2.7 indefinitely, although I doubt it.

My housemate was just rolling back from python 3.8 to 3.7 yesterday due to a backwards incompatible change breaking a library... it's not just 2 -> 3 that makes python relatively unstable compared to rust.

Yup, similar is 3.5->3.7. The community also doesn't seem to value backwards-compatiblity, judging from the libraries.

And I recently had to roll back from Python 3.9 to 3.7 to work around a couple different problems with the cffi and zstandard libraries on macOS 11.

How does library breakage reflect on Rust? Python's deprecation policy is 2 years, only a year less than that of Rust's Epoch system.

Epoch's don't break libraries - that's the whole point.

They manage this by allowing using a different epoch in a library than the application that uses it, and defaulting to the original epoch if you don't ask to use a new one.

The vast majority of rust 1.0 libraries should still work with modern rust programs, I vaguely recall that there was one minor backwards incompatible change as of a result of memory safety bug (an exception to the guarantee), but I can't remember what it was and I can't find it with google so it might actually be all rust 1.0 libraries still work.

What the issue?

It's specifically complaining about point releases of 3.x, it only mentions 2 in an unrelated way.

The fix for https://bugs.python.org/issue40870 caused me some grief when upgrading from 3.8.3 to 3.8.4 (though to be fair, the ast module has different stability guarantees).

Some industries are very very slow when it comes to upgrades. E.g. the VFX reference platform[0] only adopted python 3 for the 2020 baseline, which means many recently released products are still embedding python 2.x [1].

[0] https://vfxplatform.com/ [1] https://vfxpy.com/