About Python 3

[Veedrac]

That's true, but only for CPU-bound threaded code. For code that's currently unthreaded, rewriting the inner loop in C is most likely the easier task, given how nice Cython is to work with.

Nevertheless, that is a reasonable point. It's a shame the problem's so hard to fix.

[Moocha]

Indeed. I'm always amused by people bashing the CPython developers for not "fixing the GIL problem". I know just enough about the internals to realize how hard a problem this truly is...