Question

此处讨论multiprocessing与threading的利弊：Multiprocessing vs Threading Python

我希望使用multiprocessing在后台执行任务，同时继续执行程序的其余部分。使用threading：background function in Python

在以下问题问题中解决了此问题

import threading

def function_A(some_args):
    # some stuff

def function_B(some_args):
    #do some stuff
    my_thread = threading.Thread(target=function_A, args=my_args)
    my_thread.start()
    #continue doing stuff

我尝试使用multiprocessing：

import multiprocessing as mp

def function_A(some_args):
    # some stuff

worker_pool = mp.Pool(processes=4)

def function_B(some_args, worker_pool):
    # do some stuff
    worker_pool.apply_async(function_A, args=my_args)
    # continue doing stuff

我在测试脚本中尝试了这个：

import threading
import multiprocessing
import time


def function_A(task_description, sleep_time):
    time.sleep(sleep_time)
    print "function_A with task {} completed!\n".format(task_description)

def function_threading(sleep_time):
    st = time.time()

    for x in xrange(4):
        print "Calling A and continuing (threading)..."
        print "Time between calls: ", round(time.time() - st, 3)        
        a_thread = threading.Thread(target=function_A, args=("threading {}".format(x), sleep_time,))
        a_thread.start()
        st = time.time()

def function_multiprocessing(sleep_time, worker_pool):
    st = time.time()

    for x in xrange(4):
        print "Calling A and continuing (multiprocessing)..."
        print "Time between calls: ", round(time.time() - st, 3) 
        worker_pool.apply_async(function_A, args=("multiprocessing {}".format(x), sleep_time,))
        st = time.time()

sleep_time = 2.5

# if __name__ == "__main__" statement required for multiprocessing on Windows
if __name__ == "__main__":
    print "================================"
    print "Threading test."
    function_threading(sleep_time)
    print "================================"
    print "Multiprocessing test."
    worker_pool = multiprocessing.Pool(processes=4)
    function_multiprocessing(sleep_time, worker_pool)
    print "================================"

这是我得到的输出：

================================
Threading test.
Calling A and continuing (threading)...
Time between calls:  0.0
Calling A and continuing (threading)...
Time between calls:  0.0
Calling A and continuing (threading)...
Time between calls:  0.0
Calling A and continuing (threading)...
Time between calls:  0.001
================================
Multiprocessing test.
Calling A and continuing (multiprocessing)...
Time between calls:  0.0
Calling A and continuing (multiprocessing)...
Time between calls:  0.001
Calling A and continuing (multiprocessing)...
Time between calls:  0.0
Calling A and continuing (multiprocessing)...
Time between calls:  0.0
================================

function_A with task threading 0 completed!
function_A with task threading 2 completed!
function_A with task threading 1 completed!
function_A with task threading 3 completed!

观察：

即使主要进程被杀死之后仍然存在子进程 - 这是来自线程还是多处理？我必须按CTRL + ALT + DELETE并手动终止它们
多处理任务永不打印

需要修复哪些脚本才能正常工作？或者，换句话说，如何使用multiprocessing运行和管理后台进程？

Python：如何使用`multiprocessing`来运行后台任务？

0 个答案: