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移到3.3。

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

这是我的代码，源自第二个例子：

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.

如何让此代码按预期工作？我希望这些例子能够开箱即用。

Answer 1

这是我的错，原因有两个：

代码没有防范，即没有if __name__
看起来奇怪的Traceback是因为文件没有保存。从来没有给我造成任何问题，但在这种情况下也是如此。

更正修复错误的。

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()

按预期输出：

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

Answer 2

在Windows下，保护代码的主循环非常重要，以避免在使用processpoolexecutor或产生新进程的任何其他并行代码时递归生成子进程。

基本上，创建新进程的所有代码都必须在{product_name}之下，原因与您无法在解释器中执行它相同。

Answer 3

这实际上在Windows上仍在发生。我有Python 3.7.2，并尝试了以下文档中给出的示例 https://docs.python.org/3/library/concurrent.futures.html#concurrent.futures.ProcessPoolExecutor

即使示例已经从__name__ == '__main__'下调用了新进程，该错误仍然会发生。

我在Windows 10和Windows 7上都尝试过。它确实可以在MacOS Sierra的Mac上宣传。相同的python版本。

所有示例concurrent.futures代码都失败了“BrokenProcessPool”

3 个答案: