在 python 多处理中的进程之间使用共享值终止循环

Question

I want the loop in function 1 to be terminated once the value of var is set to 0 by process 2

var=multiprocessing.Value('i',1) #Using this variable as a shared variable between the processes.

def function1():
 #Loops until value of var is changed to 0 by function or process2
    while True:
     print("Hello")
     if var.value==0:
         break

def function2():
    print("Sleep")
    time.sleep(2)
    var.value=0
    print(var.value)

if __name__ == '__main__':
    multiprocessing.Process(target=function1).start()
    multiprocessing.Process(target=function2).start()

Answer 1

Your example works, did you put 'import time' at the beginning in your script?

Other improvements: Lock your variable before assigning a new value:

def function2():
    print("Sleep")
    time.sleep(2)
    with var.get_lock():
        var.value=0
    print(var.value)

And don't use it globally. Better define an new input variable in your function.

Final example:

#!/usr/bin/env python3

import multiprocessing, time

var=multiprocessing.Value('i',1) #Using this variable as a shared variable between the processes.

def function1(v):
 #Loops until value of var is changed to 0 by function or process2
    while True:
     print("Hello")
     if v.value==0:
         break

def function2(v):
    print("Sleep")
    time.sleep(2)
    with v.get_lock():
        v.value=0
    print(v.value)

if __name__ == '__main__':
    multiprocessing.Process(target=function1, args = [var]).start()
    multiprocessing.Process(target=function2, args = [var]).start()