Es kann Probleme beim Starten eines Prozesses mit multiprocessing durch den Aufruf __init__ geben. Hier ist eine Demo:
import multiprocessing as mp
class SubProcClass:
def __init__(self, pipe, startloop=False):
self.pipe = pipe
if startloop:
self.do_loop()
def do_loop(self):
while True:
req = self.pipe.recv()
self.pipe.send(req * req)
class ProcessInitTest:
def __init__(self, spawn=False):
if spawn:
mp.set_start_method('spawn')
(self.msg_pipe_child, self.msg_pipe_parent) = mp.Pipe(duplex=True)
def start_process(self):
subproc = SubProcClass(self.msg_pipe_child)
self.trig_proc = mp.Process(target=subproc.do_loop, args=())
self.trig_proc.daemon = True
self.trig_proc.start()
def start_process_fail(self):
self.trig_proc = mp.Process(target=SubProcClass.__init__, args=(self.msg_pipe_child,))
self.trig_proc.daemon = True
self.trig_proc.start()
def do_square(self, num):
# Note: this is an synchronous usage of mp,
# which doesn't make sense. But this is just for demo
self.msg_pipe_parent.send(num)
msg = self.msg_pipe_parent.recv()
print('{}^2 = {}'.format(num, msg))
Jetzt, mit dem obigen Code, wenn wir dies auszuführen:
if __name__ == '__main__':
t = ProcessInitTest(spawn=True)
t.start_process_fail()
for i in range(1000):
t.do_square(i)
Wir bekommen diesen Fehler:
Traceback (most recent call last):
File "start_class_process1.py", line 40, in <module>
t.start_process_fail()
File "start_class_process1.py", line 29, in start_process_fail
self.trig_proc.start()
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/multiprocessing/process.py", line 105, in start
self._popen = self._Popen(self)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/multiprocessing/context.py", line 212, in _Popen
return _default_context.get_context().Process._Popen(process_obj)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/multiprocessing/context.py", line 274, in _Popen
return Popen(process_obj)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/multiprocessing/popen_spawn_posix.py", line 33, in __init__
super().__init__(process_obj)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/multiprocessing/popen_fork.py", line 21, in __init__
self._launch(process_obj)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/multiprocessing/popen_spawn_posix.py", line 48, in _launch
reduction.dump(process_obj, fp)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/multiprocessing/reduction.py", line 59, in dump
ForkingPickler(file, protocol).dump(obj)
_pickle.PicklingError: Can't pickle <function SubProcClass.__init__ at 0x10073e510>: it's not the same object as __main__.__init__
Und wenn wir es ändern fork zu verwenden anstelle von spawn:
if __name__ == '__main__':
t = ProcessInitTest(spawn=False)
t.start_process_fail()
for i in range(1000):
t.do_square(i)
Wir bekommen diesen Fehler:
Process Process-1:
Traceback (most recent call last):
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/multiprocessing/process.py", line 254, in _bootstrap
self.run()
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/multiprocessing/process.py", line 93, in run
self._target(*self._args, **self._kwargs)
TypeError: __init__() missing 1 required positional argument: 'pipe'
Aber wenn wir nennen das start_process Methode, die nicht __init__ im mp.Process Ziel nicht nennen, wie folgt aus:
if __name__ == '__main__':
t = ProcessInitTest(spawn=False)
t.start_process()
for i in range(1000):
t.do_square(i)
Es funktioniert wie erwartet (ob wir Verwenden Sie spawn oder fork).
Ich habe einen ähnlichen Fehler nach dem Schreiben einer fehlerhaften __getstate__ Methode für ein Objekt, um seine Pickle Verhalten zu ändern. Nicht sicher, was das Problem ist, aber nach irgendwelchen von denen überprüfen. – partofthething
Ich habe das auch mit Klassen-Dekoratoren gesehen, speziell die six.add_metaclass – dbn