Question

我编写了一个继承multiprocess.Process（）的类。它在类属性中包含serial.Serial（）对象。 self.loop（）方法应该读取和写入串行端口。当调用self.loop（）时，它应该作为一个单独的进程运行，这是要求我写这个的人的要求。但是，我的代码产生了一个奇怪的错误。

这是我的代码：

from multiprocessing import Process

import serial
import time


class MySerialManager(Process):
    def __init__(self, serial_port, baudrate=115200, timeout=1):
        super(MySerialManager, self).__init__(target=self.loop)
        # As soon as you uncomment this, you'll get an error.
        # self.ser = serial.Serial(serial_port, baudrate=baudrate, timeout=timeout)

    def loop(self):
        # Just some simple action for simplicity.
        for i in range(3):
            print("hi")
            time.sleep(1)


if __name__ == "__main__":
    msm = MySerialManager("COM14")
    try:
        msm.start()
    except KeyboardInterrupt:
        print("caught in main")
    finally:
        msm.join()

这是错误：

Traceback (most recent call last):
  File "test.py", line 22, in <module>
    msm.start()
  File "C:\Python\Python36\lib\multiprocessing\process.py", line 105, in start
    self._popen = self._Popen(self)
  File "C:\Python\Python36\lib\multiprocessing\context.py", line 223, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "C:\Python\Python36\lib\multiprocessing\context.py", line 322, in _Popen
    return Popen(process_obj)
  File "C:\Python\Python36\lib\multiprocessing\popen_spawn_win32.py", line 65, in __init__
    reduction.dump(process_obj, to_child)
  File "C:\Python\Python36\lib\multiprocessing\reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
ValueError: ctypes objects containing pointers cannot be pickled

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test.py", line 26, in <module>
    msm.join()
  File "C:\Python\Python36\lib\multiprocessing\process.py", line 120, in join
    assert self._popen is not None, 'can only join a started process'
AssertionError: can only join a started process
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\Python\Python36\lib\multiprocessing\spawn.py", line 105, in spawn_main
    exitcode = _main(fd)
  File "C:\Python\Python36\lib\multiprocessing\spawn.py", line 115, in _main
    self = reduction.pickle.load(from_parent)
EOFError: Ran out of input

我还尝试在类之外创建一个串行端口对象并将其传递给构造函数。此外，我尝试不继承multiprocess.Process（），而是放置：

self.proc = Process(target=self.loop)

进入班级和

try:
    msm.proc.start()
except KeyboardInterrupt:
    print("caught in main")
finally:
    msm.proc.join()

进入主要区块。他们都没有解决问题。

有人指出，似乎混合多处理和串行端口似乎没有成功。真的吗？如果是的话，请你解释一下为什么这不起作用？非常感谢任何帮助！

Answer 1

在Windows中，一旦创建的串行对象无法在两个进程（即父级和子级）之间共享所以在子进程中创建串行对象，并将其作为参数的引用传递给其他函数

试试这个：

from multiprocessing import Process

import serial
import time


class MySerialManager(Process):
    def __init__(self, serial_port, baudrate=115200, timeout=1):
        super(MySerialManager, self).__init__(target=self.loop_iterator,args=(serial_port, baudrate, timeout))
        # As soon as you uncomment this, you'll get an error.
        # self.ser = serial.Serial(serial_port, baudrate=baudrate, timeout=timeout)

    def loop_iterator(self,serial_port, baudrate,timeout):
        ser = serial.Serial(serial_port, baudrate=baudrate, timeout=timeout)
        self.loop(ser)

    def loop(self,ser):
        # Just some simple action for simplicity.
        # you can use ser here
        for i in range(3):
            print("hi")
            time.sleep(1)


if __name__ == "__main__":
    msm = MySerialManager("COM4")
    try:
        msm.start()
    except KeyboardInterrupt:
        print("caught in main")
    finally:
        msm.join()

混合多处理和串行端口

1 个答案: