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0 pointsmasklinn5y ago0 comments

> - the only allowed file extension should be py3

That would have made cross-version codebases impossible, and that's what ultimately allowed migrating. One-shot migrations were not convenient, or successful, or even effectively feasible for complex enough projects.

What allowed the migration was community experiment in cross-version sources, as well as reintroduction of "compatibility" features into Python 3.

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antpls5y ago· 3 in thread

I dont buy this argument at all. Any sufficiently complex Python 2 project does not work with Python 3 without modification, there is _no_ cross-version compatibility.

And if you wanted to try that yourself anyway, changing all .py to .py3 in a directory is one unix command... It could easily have been part of a 2to3 tool

masklinnOP5y ago

> I dont buy this argument at all. Any sufficiently complex Python 2 project does not work with Python 3 without modification, there is _no_ cross-version compatibility.

I was personally and solely responsible for migrating a >250kLOC project from Python 2 to Python 3, doing so without cross-version compatibility would not have been feasible. We literally picked the earliest P3 version we decided to support based on cross-compatibility features.

kd5bjo5y ago

The issue is third-party libraries: They need to simultaneously support both versions of Python during the transition period. If you unilaterally migrate to v3, you break lots of existing projects. On the other hand, if you stay v2 only, you‘re holding up your dependent projects’ migration efforts.

antpls5y ago

I understand the benefit in theory, but in practice, you had two options :

- the codebase had to be modified to work on both versions at the same time

- you had to maintain two versions in different branches for a while

Is there any data to show which options was most often chosen amongst all pypi packages? I suspect that the second option was more popular for the most important packages of the ecosystem

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