python进程池multiprocessing.Pool运行错误：The freeze_support() line can be omitted if the program is not g

测试代码如下：

原文：https://blog.csdn.net/xiemanr/article/details/71700531

# -*- coding: utf-8 -*-

import multiprocessing
import timedef func(msg):print('msg: ', msg)time.sleep(1)print('----')pool = multiprocessing.Pool(processes=4)
for i in range(10):msg = 'hello world %d' % ipool.apply_async(func, (msg, ))pool.close()
pool.join()

上面的代码运行将产生如下错误信息：

RuntimeError: An attempt has been made to start a new process before thecurrent process has finished its .This probably means that you are not using fork to start yourchild processes and you have forgotten to use the proper idiomin the main module:if __name__ == '__main__':freeze_support()...The "freeze_support()" line can be omitted if the programis not going to be frozen to produce an executable.

从错误信息可以看出进程池相关代码应该放在if __name__ == '__main__'下面，代码修改如下：

# -*- coding: utf-8 -*-

import multiprocessing
import timedef func(msg):print('msg: ', msg)time.sleep(1)print('----')if __name__ == '__main__':pool = multiprocessing.Pool(processes=4)for i in range(10):msg = 'hello world %d' % ipool.apply_async(func, (msg, ))pool.close()pool.join()

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