在進程之間共享列表會引發錯誤：當我嘗試使用列表時，AttributeError: 'ForkAwareLocal' object has no attribute 'connection'

Question

我正在嘗試將列表傳遞給運行 function 以比較 colors 的進程。 然后我希望這些 colors 返回到列表中，以便我可以在進程之外的 function 中使用它。 我怎樣才能做到這一點？

到目前為止，我所擁有的只是一個縮小的問題，然后我將其簡化為示例：

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

我在 Windows 10 Home 64-bit v. 1909 上使用 Python 版本 3.7.6

Answer 1

1. 您正在創建一個列表並嘗試訪問超出范圍的索引。 在您的 function 測試中，您必須使用 append 將項目添加到列表的索引 [0]。

2. 您正在嘗試打印在“with 語句”內部但在其外部聲明的變量（顏色代碼列表）

此修改后的代碼應該可以工作：

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()