On Fri, Jun 3, 2011 at 4:28 PM, Claudiu Popa <cp...@bitdefender.com> wrote: > Hello guys, > While working at a dispatcher using > multiprocessing.connection.Listener module I've stumbled upon some > sort of magic trick that amazed me. How is this possible and > what does multiprocessing library doing in background for this to > work?
I'm not sure what magic trick you're referring to - is it that you can use dissimilar versions of Python and send strange objects? I did find that trying this in reverse (sending from 3.2, receiving with 2.7.1) failed with "ValueError: unsupported pickle protocol: 3". That, plus the docstring for send and recv, might suggest what's happening: the object gets pickled. Pickling in 2.7.1 (close enough to your 2.6 I presume): http://docs.python.org/library/pickle.html Pickling in 3.2: http://docs.python.org/py3k/library/pickle.html >From the 3.2 docs: "The pickle serialization format is guaranteed to be backwards compatible across Python releases." "Protocol version 3 was added in Python 3.0. It has explicit support for bytes and cannot be unpickled by Python 2.x pickle modules. This is the current recommended protocol, use it whenever it is possible." "The following types can be pickled: ... functions defined at the top level of a module built-in functions defined at the top level of a module ... " Presumably, the send() function pickles at the HIGHEST_PROTOCOL or DEFAULT_PROTOCOL, and recv() unpickles whatever it gets. If you do the pickling manually, you could choose to use version 2 explicitly, and then the 2.6 other end could read it comfortably. I don't know how effective the pickling of functions actually is. Someone else will doubtless be able to fill that in. Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
