python - Why wont this pickle? -

i trying run process multiprocessing, when starting thread pickler falls on , can't work out stopping pickling. i've tried commenting out socket code , message obj code, still not working - doing wrong?

class transmitthread(process):      def __init__(self, send_queue, reply_queue, control_pipe, recv_timeout=2, buffer_size=4096):         """             init function called when thread created. function calls process class init             function, , stores class vars.         """         # call process class init         process.__init__(self)          # store class vars         self.send_queue     = send_queue         self.reply_queue    = reply_queue         self.control_pipe   = control_pipe         self._recv_timeout  = recv_timeout         self._buffer_size   = buffer_size      def run(self):         """             main function called when thread started.             function loops forever, waiting send message in queue, , processes message send             , fetches response. thread loops forever until it's terminated or kill thread command             passed through control pipe.         """         # start our forever running loop         while true:              # check if there in pipe             if self.control_pipe.poll():                 # check if received kill thread command                 if self.control_pipe.recv() == kill_thread_command:                     # kill while loop , end thread                     break              # check if there in message queue             if not self.send_queue.empty():                 # fetch message queue send, , unpickle                 message_obj, message_pickle = self.send_queue.get()                  # open socket , set timeout                 sock = socket.socket(socket.af_inet, socket.sock_dgram)                 sock.settimeout(self._recv_timeout)                  # connect socket recipient                 sock.connect( message_obj.recipient_address )                  # push pickled message down socket                 sock.sendall(message_pickle)                  # check if message send request (should response)                 if str(message_obj.message_type) == str(message.request):                      print "fetching reply"                      # lets fetch response, , push pickled message onto queue                     self.reply_queue.put( sock.recv(self._buffer_size) )                      print "got reply"                  # done, close socket                 sock.close()              # add small delay stop thread consuming cpu time             sleep(0.1) 

---

the error message is:

file "c:/users/oliver/onedrive/git/pyke/pyke.py", line 127, in __init__     self.thread.start()   file "c:\python27\lib\multiprocessing\process.py", line 130, in start     self._popen = popen(self)   file "c:\python27\lib\multiprocessing\forking.py", line 277, in __init__     dump(process_obj, to_child, highest_protocol)   file "c:\python27\lib\multiprocessing\forking.py", line 199, in dump     forkingpickler(file, protocol).dump(obj)   file "c:\python27\lib\pickle.py", line 224, in dump     self.save(obj)   file "c:\python27\lib\pickle.py", line 331, in save     self.save_reduce(obj=obj, *rv)   file "c:\python27\lib\pickle.py", line 419, in save_reduce     save(state)   file "c:\python27\lib\pickle.py", line 286, in save     f(self, obj) # call unbound method explicit self   file "c:\python27\lib\pickle.py", line 649, in save_dict     self._batch_setitems(obj.iteritems())   file "c:\python27\lib\pickle.py", line 681, in _batch_setitems     save(v)   file "c:\python27\lib\pickle.py", line 286, in save     f(self, obj) # call unbound method explicit self   file "c:\python27\lib\pickle.py", line 725, in save_inst     save(stuff)   file "c:\python27\lib\pickle.py", line 286, in save     f(self, obj) # call unbound method explicit self   file "c:\python27\lib\pickle.py", line 649, in save_dict     self._batch_setitems(obj.iteritems())   file "c:\python27\lib\pickle.py", line 681, in _batch_setitems     save(v)   file "c:\python27\lib\pickle.py", line 331, in save     self.save_reduce(obj=obj, *rv)   file "c:\python27\lib\pickle.py", line 419, in save_reduce     save(state)   file "c:\python27\lib\pickle.py", line 286, in save     f(self, obj) # call unbound method explicit self   file "c:\python27\lib\pickle.py", line 649, in save_dict     self._batch_setitems(obj.iteritems())   file "c:\python27\lib\pickle.py", line 681, in _batch_setitems     save(v)   file "c:\python27\lib\pickle.py", line 331, in save     self.save_reduce(obj=obj, *rv)   file "c:\python27\lib\pickle.py", line 396, in save_reduce     save(cls)   file "c:\python27\lib\pickle.py", line 286, in save     f(self, obj) # call unbound method explicit self   file "c:\python27\lib\pickle.py", line 748, in save_global     (obj, module, name)) pickle.picklingerror: can't pickle <type 'thread.lock'>: it's not found thread.lock traceback (most recent call last):   file "<string>", line 1, in <module>   file "c:\python27\lib\multiprocessing\forking.py", line 381, in main     self = load(from_parent)   file "c:\python27\lib\pickle.py", line 1378, in load     return unpickler(file).load()   file "c:\python27\lib\pickle.py", line 858, in load     dispatch[key](self)   file "c:\python27\lib\pickle.py", line 880, in load_eof     raise eoferror eoferror 

the pickler error comes multiprocessing.process trying internally pickle subprocess. i'm pretty sure 1 of instance variables doesn't pickle child process. 1 not clear question

    # store class vars     self.send_queue     = send_queue     self.reply_queue    = reply_queue     self.control_pipe   = control_pipe     self._recv_timeout  = recv_timeout     self._buffer_size   = buffer_size 

[edit after comments op]:

the problem send_queue , reply_queue queue.queues rather multiprocessing.queue. when forking child worker, process tries serialize , instance variables on child. queue.queues local objects not serializable, hence error.

also related question fact that, multiprocessing.queue re-uses exceptions queue without re-exporting these. is documented, albeit hidden beneath clutter:

note: multiprocessing uses usual queue.empty , queue.fullexceptions signal timeout. not available in multiprocessing namespace need import them queue.