Terry J. Reedy added the comment: When quoting from the docs, it is helpful to give a link. https://docs.python.org/2/library/multiprocessing.html#examples That also identifies the version. I verified that the example fails on my 2.7.6 Windows 7 with PicklingError: Can't pickle <type 'thread.lock'>: it's not found as thread.lock Since the example has been removed for 3.x, a possible minimal fix would be to say that it does not work on Windows and remove the statement that implies that it does. if sys.platform == 'win32': import multiprocessing.reduction # make sockets pickable/inheritable ---------- nosy: +terry.reedy _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue21204> _______________________________________