I was confining myself to CPython on the grounds that it is still what people complain about in terms of adding multicore to it. People don't complain about PyPy not having it since it's still developing, and it is not yet known whether PyPy will be fast enough to be worth worrying about multicore. To be honest I'm skeptical, but open to the possibility. But I rather suspect in the end that Python will forever be a slower language than the competition; all the dynamicness doesn't come for free.
Also the nicer primitives that IMHO the really-useful multicore languages are building on are either impossible (Haskell) or too late (Go/Erlang) for Python to deeply embrace due to massive legacy libraries and code. If you want to make threading "work" in Python, go nuts, it will bring much benefit, but Python will simply never be the first choice for tasks in which multicore performance and safety is the first or second priority, rather than the fifth or sixth. And that's fine. I'd really rather see Python become a better Python than see it become a crappy Go or something.
PyPy (on it's good day) is within 2x mark from the equivalent C. We're planning on closing this gap, but also we're planning on making every day the good day (right now you kind of have to know what you're doing in case you want to hit the sweet spot). This might be an interesting read for you:
https://www2.cisl.ucar.edu/sites/default/files/2cameron_spar...
Also the nicer primitives that IMHO the really-useful multicore languages are building on are either impossible (Haskell) or too late (Go/Erlang) for Python to deeply embrace due to massive legacy libraries and code. If you want to make threading "work" in Python, go nuts, it will bring much benefit, but Python will simply never be the first choice for tasks in which multicore performance and safety is the first or second priority, rather than the fifth or sixth. And that's fine. I'd really rather see Python become a better Python than see it become a crappy Go or something.