使用python多处理模块创建的子进程将无法打印

问题描述：

我对下面的代码以及在子进程中使用print函数的任何代码有问题.即使使用sys.std[err|out].write('worker')而不是print，我也看不到任何打印的语句.

I have a problem with the code below, and with any code that uses the print function in the child processes. I can't see any printed statements, even if I use sys.std[err|out].write('worker') instead of print.

这是代码(来自官方python文档的 ):

This is the code (from the official python documentation):

from multiprocessing import Process

def f(name):
    print 'hello', name

if __name__ == '__main__':
    p = Process(target=f, args=('bob',))
    p.start()
    p.join()

输出为空白.

注意:以下代码使用线程模块并打印输出:

Note: The following code uses the threading module and it prints the output:

import threading

def f(name):
    print 'hello', name

if __name__ == '__main__':
    p = threading.Thread(target=f, args=('bob',))
    p.start()
    p.join()

输出:hello bob

能否请您指出解决方案?预先感谢.

Can you please point me to the solution? Thanks in advance.

答

尝试一下:

from multiprocessing import Process
import sys

def f(name):
    print 'hello', name
    sys.stdout.flush()

...

AFAIK缓冲了由multiprocessing模块生成的已处理标准输出，因此，只有在缓冲区已满或显式刷新sys.stdout时，您才可以看到输出.

AFAIK the standard output of processed spawned by the multiprocessing module is buffered, hence you will see the output only if the buffer becomes full or you explicitly flush sys.stdout.

使用python多处理模块创建的子进程将无法打印

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