I am trying to return values from subprocesses but these values are unfortunately unpicklable. So I used global variables in threads module with success but have not been able to retrieve updates done in subprocesses when using multiprocessing module. I hope I'm missing something. The results printed at the end are always the same as initial values given the vars dataDV03 and dataDV04. The subprocesses are updating these global variables but these global variables remain unchanged in the parent. import multiprocessing # NOT ABLE to get python to return values in passed variables. ants = ['DV03', 'DV04'] dataDV03 = ['', ''] dataDV04 = {'driver': '', 'status': ''} def getDV03CclDrivers(lib): # call global variable global dataDV03 dataDV03[1] = 1 dataDV03[0] = 0 # eval( 'CCL.' + lib + '.' + lib + '( "DV03" )' ) these are unpicklable instantiations def getDV04CclDrivers(lib, dataDV04): # pass global variable dataDV04['driver'] = 0 # eval( 'CCL.' + lib + '.' + lib + '( "DV04" )' ) if __name__ == "__main__": jobs = [] if 'DV03' in ants: j = multiprocessing.Process(target=getDV03CclDrivers, args=('LORR',)) jobs.append(j) if 'DV04' in ants: j = multiprocessing.Process(target=getDV04CclDrivers, args=('LORR', dataDV04)) jobs.append(j) for j in jobs: j.start() for j in jobs: j.join() print 'Results:\n' print 'DV03', dataDV03 print 'DV04', dataDV04 I cannot post to my question so will try to edit the original. Here is the object that is not picklable: In [1]: from CCL import LORR In [2]: lorr=LORR.LORR('DV20', None) In [3]: lorr Out[3]: <CCL.LORR.LORR instance at 0x94b188c> This is the error returned when I use a multiprocessing.Pool to return the instance back to the parent: Thread getCcl (('DV20', 'LORR'),) Process PoolWorker-1: Traceback (most recent call last): File "/alma/ACS-10.1/casa/lib/python2.6/multiprocessing/process.py", line 232, in _bootstrap self.run() File "/alma/ACS-10.1/casa/lib/python2.6/multiprocessing/process.py", line 88, in run self._target(*self._args, **self._kwargs) File "/alma/ACS-10.1/casa/lib/python2.6/multiprocessing/pool.py", line 71, in worker put((job, i, result)) File "/alma/ACS-10.1/casa/lib/python2.6/multiprocessing/queues.py", line 366, in put return send(obj) UnpickleableError: Cannot pickle <type 'thread.lock'> objects In [5]: dir(lorr) Out[5]: ['GET_AMBIENT_TEMPERATURE', 'GET_CAN_ERROR', 'GET_CAN_ERROR_COUNT', 'GET_CHANNEL_NUMBER', 'GET_COUNT_PER_C_OP', 'GET_COUNT_REMAINING_OP', 'GET_DCM_LOCKED', 'GET_EFC_125_MHZ', 'GET_EFC_COMB_LINE_PLL', 'GET_ERROR_CODE_LAST_CAN_ERROR', 'GET_INTERNAL_SLAVE_ERROR_CODE', 'GET_MAGNITUDE_CELSIUS_OP', 'GET_MAJOR_REV_LEVEL', 'GET_MINOR_REV_LEVEL', 'GET_MODULE_CODES_CDAY', 'GET_MODULE_CODES_CMONTH', 'GET_MODULE_CODES_DIG1', 'GET_MODULE_CODES_DIG2', 'GET_MODULE_CODES_DIG4', 'GET_MODULE_CODES_DIG6', 'GET_MODULE_CODES_SERIAL', 'GET_MODULE_CODES_VERSION_MAJOR', 'GET_MODULE_CODES_VERSION_MINOR', 'GET_MODULE_CODES_YEAR', 'GET_NODE_ADDRESS', 'GET_OPTICAL_POWER_OFF', 'GET_OUTPUT_125MHZ_LOCKED', 'GET_OUTPUT_2GHZ_LOCKED', 'GET_PATCH_LEVEL', 'GET_POWER_SUPPLY_12V_NOT_OK', 'GET_POWER_SUPPLY_15V_NOT_OK', 'GET_PROTOCOL_MAJOR_REV_LEVEL', 'GET_PROTOCOL_MINOR_REV_LEVEL', 'GET_PROTOCOL_PATCH_LEVEL', 'GET_PROTOCOL_REV_LEVEL', 'GET_PWR_125_MHZ', 'GET_PWR_25_MHZ', 'GET_PWR_2_GHZ', 'GET_READ_MODULE_CODES', 'GET_RX_OPT_PWR', 'GET_SERIAL_NUMBER', 'GET_SIGN_OP', 'GET_STATUS', 'GET_SW_REV_LEVEL', 'GET_TE_LENGTH', 'GET_TE_LONG_FLAG_SET', 'GET_TE_OFFSET_COUNTER', 'GET_TE_SHORT_FLAG_SET', 'GET_TRANS_NUM', 'GET_VDC_12', 'GET_VDC_15', 'GET_VDC_7', 'GET_VDC_MINUS_7', 'SET_CLEAR_FLAGS', 'SET_FPGA_LOGIC_RESET', 'SET_RESET_AMBSI', 'SET_RESET_DEVICE', 'SET_RESYNC_TE', 'STATUS', '_HardwareDevice__componentName', '_HardwareDevice__hw', '_HardwareDevice__stickyFlag', '_LORRBase__logger', '__del__', '__doc__', '__init__', '__module__', '_devices', 'clearDeviceCommunicationErrorAlarm', 'getControlList', 'getDeviceCommunicationErrorCounter', 'getErrorMessage', 'getHwState', 'getInternalSlaveCanErrorMsg', 'getLastCanErrorMsg', 'getMonitorList', 'hwConfigure', 'hwDiagnostic', 'hwInitialize', 'hwOperational', 'hwSimulation', 'hwStart', 'hwStop', 'inErrorState', 'isMonitoring', 'isSimulated'] In [6]: