[mytherin]

The hardest part about optimizing Python is the fact that there are so many packages out there relying on every single documented and undocumented aspect of the C/C++ interface, which is incredibly broad and directly tied to the internals of the language. If they change anything in a non-backwards compatible manner many of those packages will break, and those packages are the reason so many people use Python to begin with.

Javascript never had this problem, as all code was always written in Javascript itself by necessity, so it was far easier to optimize as you did not have to worry about backwards compatibility of the internals.

[cdavid]

That's a excellent point. That ecosystem is also one of the main reason packaging in python is a bit of a clusterf*ck.

For C/C++ extensions, I think there may be hope to support a slow/emulating C API and a faster, less internals-leaking new API that extensions could adopt. It would take years for the migration, but if speed gains was say 5x, I think it could be realistic.

pypy managed to emulate the C API fairly well, after all. E.g. you can build numpy and pandas on top of pypy and it actually kinda works.