multiprocessing needs to be guarded on windows

Was experimenting with dronecan and couldn't get it working with my script Started a script based on the guides here

I then tried the example dump_all.py It was also showing the same behaviour

It was crashing with the following:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\multiprocessing\spawn.py", line 116, in spawn_main
    exitcode = _main(fd, parent_sentinel)
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\multiprocessing\spawn.py", line 125, in _main
    prepare(preparation_data)
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\multiprocessing\spawn.py", line 236, in prepare
    _fixup_main_from_path(data['init_main_from_path'])
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\multiprocessing\spawn.py", line 287, in _fixup_main_from_path
    main_content = runpy.run_path(main_path,
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\runpy.py", line 269, in run_path    
    return _run_module_code(code, init_globals, run_name,
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\runpy.py", line 96, in _run_module_code
    _run_code(code, mod_globals, init_globals,
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\runpy.py", line 86, in _run_code    
    exec(code, run_globals)
  File "c:\Users\CalebStott\Desktop\dump_all.py", line 18, in <module>
    node = dronecan.make_node(args.port, node_id=args.node_id, bitrate=args.bitrate)
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\site-packages\dronecan\node.py", line 538, in make_node
    can = driver.make_driver(can_device_name, **kwargs)
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\site-packages\dronecan\driver\__init__.py", line 58, in make_driver
    return MAVCAN(device_name, **kwargs)
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\site-packages\dronecan\driver\mavcan.py", line 194, in __init__
    self.proc.start()
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\multiprocessing\process.py", line 121, in start
    self._popen = self._Popen(self)
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\multiprocessing\context.py", line 224, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\multiprocessing\context.py", line 327, in _Popen
    return Popen(process_obj)
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\multiprocessing\popen_spawn_win32.py", line 45, in __init__
    prep_data = spawn.get_preparation_data(process_obj._name)
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\multiprocessing\spawn.py", line 154, in get_preparation_data
    _check_not_importing_main()
  File "C:\Users\CalebStott\AppData\Local\Programs\Python\Python310\lib\multiprocessing\spawn.py", line 134, in _check_not_importing_main
    raise RuntimeError(
RuntimeError:
        An attempt has been made to start a new process before the
        current process has finished its bootstrapping phase.

        This probably means that you are not using fork to start your
        child processes and you have forgotten to use the proper idiom
        in the main module:

            if __name__ == '__main__':
                freeze_support()
                ...

        The "freeze_support()" line can be omitted if the program
        is not going to be frozen to produce an executable.

after some digging seems to be windows related with multiprocessing adding the following fixed the issue

from multiprocessing import freeze_support
if __name__ == "__main__":
    freeze_support()
    node = dronecan.make_node(...

might be worth noting this in documentation for windows users

dronecan / pydronecan

multiprocessing needs to be guarded on windows #54