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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"RecursionError when unpickling message object","articleBody":"Python 3.7.5\r\npython-can 3.3.2\r\n\r\nTo hand over messages to another process I intended to use multiprocessing.JoinableQueue.\r\nI stumbled over a RecursionError and tracked it down to the pickleing that is used to serialize the objects (see example code).\r\n\r\nThe error occurs when calling loads() on the serialized message.\r\n\r\nI'm not a python expert and found some clues regarding the \\_\\_getattr\\_\\_ method. Maybe a custom \\_\\_getattr\\_\\_ method is needed for the message objects?\r\n\r\nIs there another way to hand over the emssage objects to another process?\r\n\r\n~~~\r\n#!/usr/bin/env python3\r\nimport can\r\nimport logging\r\nimport pickle\r\n\r\nclass CanReader():\r\n    \"\"\"\r\n    Reads messages from a configured can bus and puts them into a queue for further processing\r\n    \"\"\"\r\n\r\n    def __init__(self):\r\n        LOG_FORMAT = '%(asctime)s:%(threadName)s:%(levelname)s: %(message)s'\r\n        logging.basicConfig(format=LOG_FORMAT, level=logging.INFO)\r\n\r\n\r\n    def run(self):\r\n        can.rc['interface'] = 'socketcan_ctypes'\r\n        can.rc['channel'] = \"vcan0\"\r\n\r\n        can_bus = can.interface.Bus()\r\n\r\n        try:\r\n            for can_msg in can_bus:\r\n                if can_msg is  None:\r\n                    continue\r\n\r\n                pick = pickle.dumps(can_msg)\r\n                logging.info(\"pickled\")\r\n                unpick = pickle.loads(pick)\r\n                logging.info(\"unpickled\")\r\n\r\n        except KeyboardInterrupt:\r\n            logging.error(\"KeyboardInterrupt - Stopping CanReader\")\r\n\r\n        return\r\n\r\nif __name__ == \"__main__\":\r\n    canReader = CanReader()\r\n    canReader.run()\r\n~~~\r\n\r\n\r\nConsole output:\r\n~~~\r\n/usr/bin/python3.7 /XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/SerializationTest.py\r\n2020-04-02 13:35:59,352:MainThread:INFO: Created a socket\r\n2020-04-02 13:35:59,389:MainThread:INFO: pickled\r\nTraceback (most recent call last):\r\n  File \"/XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/SerializationTest.py\", line 39, in \u003cmodule\u003e\r\n    canReader.run()\r\n  File \"/XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/SerializationTest.py\", line 29, in run\r\n    unpick = pickle.loads(pick)\r\n  File \"/home/XXXXXX/.local/lib/python3.7/site-packages/can/message.py\", line 59, in __getattr__\r\n    return self._dict[key]\r\n  File \"/home/XXXXXX/.local/lib/python3.7/site-packages/can/message.py\", line 59, in __getattr__\r\n    return self._dict[key]\r\n  File \"/home/XXXXXX/.local/lib/python3.7/site-packages/can/message.py\", line 59, in __getattr__\r\n    return self._dict[key]\r\n  [Previous line repeated 494 more times]\r\n  File \"/home/XXXXXX/.local/lib/python3.7/site-packages/can/message.py\", line 58, in __getattr__\r\n    warnings.warn(\"Custom attributes of messages are deprecated and will be removed in 4.0\", DeprecationWarning)\r\nRecursionError: maximum recursion depth exceeded while calling a Python object\r\n\r\nProcess finished with exit code 1\r\n~~~","author":{"url":"https://github.com/fpetry","@type":"Person","name":"fpetry"},"datePublished":"2020-04-02T11:46:28.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/804/python-can/issues/804"}