pypy also supports stackless style microthreads: http://codespeak.net/pypy/dist/pypy/doc/stackless.html http://codespeak.net/pypy/dist/pypy/doc/stackless.html b

pypy also supports stackless style microthreads: http://codespeak.net/pypy/dist/pypy/doc/stackless.html http://codespeak.net/pypy/dist/pypy/doc/stackless.html but, yes, system level threads are GIL based.