问题描述

我想在一个类中使用 Pool，但似乎有问题.我的代码很长，我创建了一个小型演示变体来说明问题.如果您能给我下面的代码变体，那就太好了.

I would like to use Pool within a class, but there seems to be a problem. My code is long, I created a small-demo variant to illustrated the problem. It would be great if you can give me a variant of the code below that works.

from multiprocessing import Pool

class SeriesInstance(object):
    def __init__(self):
        self.numbers = [1,2,3]
    def F(self, x):
        return x * x
    def run(self):
        p = Pool()
        print p.map(self.F, self.numbers)


ins = SeriesInstance()
ins.run()

输出:

Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/lib64/python2.7/threading.py", line 551, in __bootstrap_inner
    self.run()
  File "/usr/lib64/python2.7/threading.py", line 504, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib64/python2.7/multiprocessing/pool.py", line 319, in _handle_tasks
    put(task)
PicklingError: Can't pickle <type 'instancemethod'>: attribute lookup __builtin__.instancemethod failed

然后挂起.

推荐答案

不幸的是，由于函数被传递给工作线程(酸洗)的方式，你不能使用实例方法.我的第一个想法是使用 lambdas，但事实证明内置的 pickler can't 序列化它们. 遗憾的是，解决方案只是在全局命名空间中使用一个函数.不过，您仍然可以将其设为实例属性，请看:

It looks like because of the way the function gets passed to the worker threads (pickling) you can't use instance methods unfortunately. My first thought was to use lambdas, but it turns out the built in pickler can't serialize those either. The solution, sadly, is just to use a function in the global namespace. You can still make it an instance attribute though, take a look:

from multiprocessing import Pool

def F(x):
    return x * x

class SeriesInstance(object):
    def __init__(self):
        self.numbers = [1,2,3]
        self.F = F

    def run(self):
        p = Pool()
        out = p.map(self.F, self.numbers)
        p.close()
        p.join()
        return out

if __name__ == '__main__':
    print SeriesInstance().run()

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