所有示例concurrent.futures代码都失败，返回“brokenprocessspool”

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改到3.3。

直接复制粘贴this code from the python docs失败，就像here中的一个稍微简单的示例一样。

这是我的代码，来自第二个示例：

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.

如何使此代码按预期工作？我希望这些例子能开箱即用。

Answer 1

在Windows下，当使用processpoolexecutor或任何其他生成新进程的并行代码时，保护代码的主循环以避免子进程的递归生成非常重要。

基本上，所有创建新进程的代码都必须在if __name__ == '__main__':下，因为同样的原因，您不能在解释器中执行它。