That's not the concern. Python already has threads and race conditions (although the GIL means that the interpreter itself probably won't get corrupted while ex

That's not the concern. Python already has threads and race conditions (although the GIL means that the interpreter itself probably won't get corrupted while executing a piece of bytecode). What python doesn't have is a C api for extensions that makes sense without a GIL. So ideally a correct threadsafe C extension will continue to be correct, which probably implies that a function called "PyEval_AcquireLock" will continue to provide similar guarantees. Which means that the process for utilizing more cores with pure python code in one process will probably be a gradual upgrade process.