Windows上的RuntimeError尝试Python多处理

Question

我正在Windows机器上尝试使用Threading and
Multiprocessing的第一个正式python程序。我无法启动进程，但是python给出了以下消息。问题是，我没有在 主
模块中启动线程。线程在类内的单独模块中处理。

编辑 ：顺便说一句，此代码在ubuntu上运行良好。在窗户上不太

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.

我的原始代码很长，但是我能够以节略的版本重现该错误。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外，几乎没有其他作用。第二个模块是代码的关键所在。

testMain.py：

import parallelTestModule

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

parallelTestModule.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()

Answer 1

在Windows上，子进程将在启动时导入（即执行）主模块。您需要if __name__ == '__main__':在主模块中插入防护，以避免递归创建子流程。

已修改testMain.py：

import parallelTestModule

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