尝试python多处理的Windows上的RuntimeError

Question

我正在尝试在Windows机器上使用线程和多处理的第一个正式的python程序.我无法启动进程,python提供以下消息.问题是,我没有在主模块中启动我的线程.线程在类中的单独模块中处理.

编辑:顺便说一句,这个代码在ubuntu上正常运行.不是在窗户上

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,但我能够在删节版本的代码中重现错误.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,它只做很少的事情.第二个模块是代码的核心所在.

---

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__':在主模块中插入一个保护,以避免递归地创建子进程.

修改testMain.py:

import parallelTestModule

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

Answer 2

尝试将代码放在testMain.py中的main函数中

import parallelTestModule

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

查看文档:

"For an explanation of why (on Windows) the if __name__ == '__main__' 
part is necessary, see Programming guidelines."

哪个说

"确保新的Python解释器可以安全地导入主模块,而不会导致意外的副作用(例如启动新进程)."

... 通过使用 if __name__ == '__main__'

Answer 3

你好，这是我的多进程结构

from multiprocessing import Process
import time


start = time.perf_counter()


def do_something(time_for_sleep):
    print(f'Sleeping {time_for_sleep} second...')
    time.sleep(time_for_sleep)
    print('Done Sleeping...')



p1 = Process(target=do_something, args=[1])
p2 = Process(target=do_something, args=[2])


if __name__ == '__main__':
    p1.start()
    p2.start()

    p1.join()
    p2.join()

    finish = time.perf_counter()
    print(f'Finished in {round(finish-start,2 )} second(s)')

您不必将导入放入 中if __name__ == '__main__':，只需运行您希望在其中运行的程序即可

Answer 4

正如@Ofer所说，当你使用其他库或模块时，你应该将它们全部导入到if __name__ == '__main__':

所以，就我而言，结局是这样的：

if __name__ == '__main__':       
    import librosa
    import os
    import pandas as pd
    run_my_program()

Answer 5

尽管较早的答案是正确的，但有一点复杂之处将有助于进一步说明。

如果您的主模块导入了另一个模块，在该模块中定义了全局变量或类成员变量并将其初始化为（或使用）一些新对象，则可能必须以相同的方式来限制导入：

if __name__ ==  '__main__':
  import my_module