[throwaway894345]

> So if one day RustPython gets compatible enought with CPython that you can use it as a drop in replacement

I don't think this will ever happen unless the community converges on a standard C-extension interface. Presently Python leans so hard on C-extensions, but there is no standard interface--if you're writing a C-extension library, you just depend on whatever obscure corner of CPython that suits your purpose. If you're writing an alternative Python interpreter, you have to implement the entire surface area of CPython, which generally means you must implement CPython exactly and you are severely restricted on the improvements you can make. At that point, why even bother?

Fortunately, I think there are emerging candidate interfaces, but the community needs to either update C-extension packages to use those interfaces or support packages (and maintainers) who already do. https://github.com/pyhandle/hpy.

[BiteCode_dev]

There are probably only a dozen of c popular extensions that needs to support HPY reach the tipping point of mass adoption: numpy, scipy, pycuda, tensorflow, matplotlib, uvloop, etc. and some db drivers.

The rest is not popular enought to be a blocker. You will hear them scream a lot, but they will be like 0.00001% of the user base, and we can just tell them to stay on CPython with its limitations. They don't lose anything, just not gain anything either.

Those C extensions authors are directly in communication with Python core devs, when they are not core devs themselves, so if HPY is adopted, we can expect a total adoption under 5 years.

Numpy authors already said it would take 1 year to adopt it.

Give the huge number of benefits of HPY, I deeply hope it will be a success.

[throwaway894345]

I'm not sure. I would certainly add psycopg2 to that list, since it's really the only well-supported way to speak to a Postgres database via Python. I imagine other database dialects will have similar issues. And there's probably a whole host of other prominent libraries that we're just not thinking about because we only run into them when we're trying to use something like Pypy, and even then we only run into one or two at a time before giving up and going back to CPython.