python - 所有示例 concurrent.futures 代码都失败并显示 "BrokenProcessPool"

Question

在创建我需要的实际应用程序之前，我试图对此有一个基本的了解。我最近从 2.7 转移到了 3.3。

this code from the python docs 的直接复制粘贴失败，来自 here 的一个稍微简单的例子也是如此.

这是我的代码，源自第二个示例:

import concurrent.futures

nums = [1,2,3,4,5,6,7,8,9,10]

def f(x):
    return x * x

# Make sure the map and function are working
print([val for val in map(f, nums)])

# Test to make sure concurrent map is working
with concurrent.futures.ProcessPoolExecutor() as executor:
    for item in executor.map(f, nums):
        print(item)

这是输出:

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
Traceback (most recent call last):
  File "<string>", line 420, in run_nodebug
  File "<module1>", line 13, in <module>
  File "C:\Python33\lib\concurrent\futures\_base.py", line 546, in result_iterator
    yield future.result()
  File "C:\Python33\lib\concurrent\futures\_base.py", line 399, in result
    return self.__get_result()
  File "C:\Python33\lib\concurrent\futures\_base.py", line 351, in __get_result
    raise self._exception
concurrent.futures.process.BrokenProcessPool: A process in the process pool was terminated abruptly while the future was running or pending.

如何让这段代码按预期工作？我希望这些示例开箱即用。

Answer 1

这是我的错，有两个原因:

1. 代码未 protected ，即没有if __name__
2. 看起来很奇怪的 Traceback 是因为文件没有保存。以前从来没有给我带来过问题，但在这种情况下却造成了。

更正两个的错误。

最终测试代码:

import concurrent.futures

nums = [1,2,3,4,5,6,7,8,9,10]

def f(x):
    return x * x
def main():
    # Make sure the map and function are working
    print([val for val in map(f, nums)])

    # Test to make sure concurrent map is working
    with concurrent.futures.ProcessPoolExecutor() as executor:
        print([val for val in executor.map(f, nums)])

if __name__ == '__main__':
    main()

输出，如预期:

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]