Pure Python code can do a lot. Large parts of the stdlib are extension modules, and can release the GIL (e.g. one of the tests on the bug tracker used time.slee

Pure Python code can do a lot. Large parts of the stdlib are extension modules, and can release the GIL (e.g. one of the tests on the bug tracker used time.sleep()). In practice, if your code is IO-bound, it's doing work in an extension module, and if it's CPU-bound, it should be doing its work in an extension module. So there's actually not a huge problem.