Windows 上尝试 python 多处理时出现运行时错误

我正在 Windows 机器上使用线程和多处理来尝试我的第一个正式的 python 程序。但我无法启动进程，Python 给出以下消息。问题是，我没有在main模块。线程在类内的单独模块中处理。

EDIT：顺便说一句，这段代码在 ubuntu 上运行良好。不太适合 Windows

RuntimeError: 
            Attempt to start a new process before the current process
            has finished its bootstrapping phase.
            This probably means that you are on Windows and you have
            forgotten to use the proper idiom in the main module:
                if __name__ == '__main__':
                    freeze_support()
                    ...
            The "freeze_support()" line can be omitted if the program
            is not going to be frozen to produce a Windows executable.

我的原始代码相当长，但我能够在代码的删节版本中重现该错误。它分为两个文件，第一个是主模块，除了导入处理进程/线程和调用方法的模块之外，几乎不做任何事情。第二个模块是代码的核心所在。

测试主.py：

import parallelTestModule

extractor = parallelTestModule.ParallelExtractor()
extractor.runInParallel(numProcesses=2, numThreads=4)

并行测试模块.py：

import multiprocessing
from multiprocessing import Process
import threading

class ThreadRunner(threading.Thread):
    """ This class represents a single instance of a running thread"""
    def __init__(self, name):
        threading.Thread.__init__(self)
        self.name = name
    def run(self):
        print self.name,'\n'

class ProcessRunner:
    """ This class represents a single instance of a running process """
    def runp(self, pid, numThreads):
        mythreads = []
        for tid in range(numThreads):
            name = "Proc-"+str(pid)+"-Thread-"+str(tid)
            th = ThreadRunner(name)
            mythreads.append(th) 
        for i in mythreads:
            i.start()
        for i in mythreads:
            i.join()

class ParallelExtractor:    
    def runInParallel(self, numProcesses, numThreads):
        myprocs = []
        prunner = ProcessRunner()
        for pid in range(numProcesses):
            pr = Process(target=prunner.runp, args=(pid, numThreads)) 
            myprocs.append(pr) 
#        if __name__ == 'parallelTestModule':    #This didnt work
#        if __name__ == '__main__':              #This obviously doesnt work
#        multiprocessing.freeze_support()        #added after seeing error to no avail
        for i in myprocs:
            i.start()

        for i in myprocs:
            i.join()

在 Windows 上，子进程将在启动时导入（即执行）主模块。您需要插入一个if __name__ == '__main__':在主模块中进行保护以避免递归创建子流程。

修改的testMain.py:

import parallelTestModule

if __name__ == '__main__':    
    extractor = parallelTestModule.ParallelExtractor()
    extractor.runInParallel(numProcesses=2, numThreads=4)