[mytherin]

It is possible to JIT compile Python just fine. There are projects like PyPy that have been doing this for a long time [1]. The reason these alternative projects never take off is because many of Python's most used libraries are written against CPython's C API. This API is giant, and exposes all of the nitty gritty implementation details of the CPython interpreter. As a result, changing anything significant about the implementation of the interpreter means those libraries no longer work. In order to not break compatibility with the enormous amounts of packages the internals of the CPython interpreter are mostly locked in at this point with little wiggle room for large performance improvements.

The only real way out is to make Python 4 - but given the immense pain of the Python 2 -> 3 transition that seems unlikely.

[1] https://www.pypy.org

[bb88]

To be fair the 2 -> 3 upgrade path was terrible. And there wasn't a killer feature in 3 which was terrible. And the tooling around the upgrade was terrible. Basically the python devs completely botched it -- which was terrible.

So one thing of golang that is nice is that go 1.19 compiler will compile go 1.1 just fine, and people can iterate from 1.1 to 1.19 in their own time -- or not if they choose not to. It would not be that hard for golang v2 to continue to allow similar compilation of old code.

[thayne]

this hypothetical 3 -> 4 upgrade would run into a lot of the same issues.

Presumably the killer feature here is that it would be faster. Or at least have the potential to be faster because of less constraints on the c API. But for a lot of python applications, speed isn't all that important. After all, if it really needs to be fast, you probably aren't doing it in python (unless python is just a thin wrapper around a lot of c code like numpy).

And for changes to the C API, it would probably much, much harder, maybe even impossible to automate migrating libraries to the new API. The only way I could see this working well is if you had some kind of shim library between the old API and the new API, but that adds constraints on how much you can change the API, and might add additional overhead.

[pkkm]

The HPy project [0] looks like a promising way out of this.

[0] https://hpyproject.org/