在进程之间共享列表会引发错误：AttributeError:“ForkAwareLocal”对象在我尝试使用列表时没有属性“connection”

Question

我试图将一个列表传递给一个进程，该进程运行一个函数来比较颜色。然后我希望这些颜色返回到列表中，这样我就可以在进程之外的函数中使用它。我该怎么做

到目前为止，我所拥有的只是一个缩小的问题，然后我将其简化为示例：

import multiprocessing


def test(c):
    c[0] = 1


class TestClass:
    def __init__(self):
        with multiprocessing.Manager() as manager:
            colorcodes = manager.list()
            p = multiprocessing.Process(target=test, args=(colorcodes,))
            p.start()
            p.join()
        print(colorcodes[0])


if __name__ == '__main__':
    TestClass()

返回：

Process Process-2:
Traceback (most recent call last):
  File "C:\Users\usr\AppData\Local\Programs\Python\Python37\lib\multiprocessing\process.py", line 297, in _bootstrap
    self.run()
  File "C:\Users\usr\AppData\Local\Programs\Python\Python37\lib\multiprocessing\process.py", line 99, in run
    self._target(*self._args, **self._kwargs)
  File "D:\Python Development\example_env\example.py", line 5, in test
    c[0] = 1
  File "<string>", line 2, in __setitem__
  File "C:\Users\usr\AppData\Local\Programs\Python\Python37\lib\multiprocessing\managers.py", line 834, in _callmethod
    raise convert_to_error(kind, result)
IndexError: list assignment index out of range
Traceback (most recent call last):
  File "C:\Users\usr\AppData\Local\Programs\Python\Python37\lib\multiprocessing\managers.py", line 811, in _callmethod
    conn = self._tls.connection
AttributeError: 'ForkAwareLocal' object has no attribute 'connection'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "example.py", line 19, in <module>
    TestClass()
  File "example.py", line 15, in __init__
    print(colorcodes[0])
  File "<string>", line 2, in __getitem__
  File "C:\Users\usr\AppData\Local\Programs\Python\Python37\lib\multiprocessing\managers.py", line 815, in _callmethod
    self._connect()
  File "C:\Users\usr\AppData\Local\Programs\Python\Python37\lib\multiprocessing\managers.py", line 802, in _connect
    conn = self._Client(self._token.address, authkey=self._authkey)
  File "C:\Users\usr\AppData\Local\Programs\Python\Python37\lib\multiprocessing\connection.py", line 490, in Client
    c = PipeClient(address)
  File "C:\Users\usr\AppData\Local\Programs\Python\Python37\lib\multiprocessing\connection.py", line 691, in PipeClient
    _winapi.WaitNamedPipe(address, 1000)
FileNotFoundError: [WinError 2] The system cannot find the file specified

我正在Windows 10 Home 64位v上使用Python版本3.7.6。1909年

Answer 1

1. 您正在创建列表并试图访问超出范围的索引。在函数测试中，必须使用append将项添加到列表的索引[0]

2. 您正试图打印一个变量（颜色代码列表），该变量在“with statement”内部声明，但在其外部声明

修改后的代码应该可以工作：

import multiprocessing


def test(c):
    c.append(1)


class TestClass:
    def __init__(self):
        with multiprocessing.Manager() as manager:
            colorcodes = manager.list()
            p = multiprocessing.Process(target=test, args=(colorcodes,))
            p.start()
            p.join()
            print(colorcodes[0])



if __name__ == '__main__':
    TestClass()