例子：对同一个数字进行加法运算
没有使用锁的程序如下：
[root@web thread_process]# cat multi3.py #!/usr/bin/env python import multiprocessing import time def add(number, increment, lock): print 'init number{0} = {1}'.format(increment, number) for i in xrange(5): number += increment time.sleep(1) print 'add number{0} = {1}'.format(increment, number) if __name__ == '__main__': number = 0 lock = multiprocessing.Lock() p1 = multiprocessing.Process(target=add, args=(number, 1, lock)) //没有加锁时，子进程各自独立运行，两个子进程同时都对number进行加法运算 p2 = multiprocessing.Process(target=add, args=(number, 3, lock)) p1.start() p2.start() print 'main end' [root@web thread_process]# python multi3.py main end init number3 = 0 init number1 = 0 add number3 = 3 //结果是无序排列的 add number1 = 1 add number3 = 6 add number1 = 2 add number3 = 9 add number1 = 3 add number1 = 4 add number3 = 12 add number1 = 5 add number3 = 15
使用锁的程序如下：
[root@web thread_process]# cat multi3.py #!/usr/bin/env python import multiprocessing import time def add(number, increment, lock): with lock: print 'init number{0} = {1}'.format(increment, number) for i in xrange(5): number += increment time.sleep(1) print 'add number{0} = {1}'.format(increment, number) if __name__ == '__main__': number = 0 lock = multiprocessing.Lock() p1 = multiprocessing.Process(target=add, args=(number, 1, lock)) p2 = multiprocessing.Process(target=add, args=(number, 3, lock)) p1.start() p2.start() print 'main end' [root@web thread_process]# python multi3.py main end init number1 = 0 //谁先抢到锁谁先运行，另外一个被阻塞，直到当前锁被释放 add number1 = 1 add number1 = 2 add number1 = 3 add number1 = 4 add number1 = 5 init number3 = 0 add number3 = 3 add number3 = 6 add number3 = 9 add number3 = 12 add number3 = 15
加锁的另外一种写法：
[root@web thread_process]# cat multi3.py #!/usr/bin/env python import multiprocessing import time def add(number, increment, lock): lock.acquire() try: print 'init number{0} = {1}'.format(increment, number) for i in xrange(5): number += increment time.sleep(1) print 'add number{0} = {1}'.format(increment, number) except Exception as e: raise e finally: lock.release() if __name__ == '__main__': number = 0 lock = multiprocessing.Lock() p1 = multiprocessing.Process(target=add, args=(number, 1, lock)) p2 = multiprocessing.Process(target=add, args=(number, 3, lock)) p1.start() p2.start() print 'main end' [root@web thread_process]# python multi3.py main end init number3 = 0 add number3 = 3 add number3 = 6 add number3 = 9 add number3 = 12 add number3 = 15 init number1 = 0 add number1 = 1 add number1 = 2 add number1 = 3 add number1 = 4 add number1 = 5
Value的例子：
[root@web thread_process]# cat multi4.py #!/usr/bin/env python import multiprocessing import time def add(number, increment): try: print 'init number{0} = {1}'.format(increment, number.value) for i in xrange(5): number.value += increment time.sleep(1) print 'add number{0} = {1}'.format(increment, number.value) except Exception as e: raise e if __name__ == '__main__': number = multiprocessing.Value('i', 0) //定义共享对象 # number.value //获得共享对象 p1 = multiprocessing.Process(target=add, args=(number, 1)) p2 = multiprocessing.Process(target=add, args=(number, 3)) p1.start() p2.start() print 'main end' #加不加锁都可以，加锁的话显示的结果顺序会好看点 [root@web thread_process]# python multi4.py main end init number1 = 0 //其中一个子进程对number赋值为0 init number3 = 1 //另一个子进程获得共享的number的值0，然后+1=1 add number3 = 4 add number1 = 7 add number3 = 8 add number1 = 11 add number1 = 12 add number3 = 13 add number3 = 16 add number1 = 19 add number3 = 20 //区别：没有定义number为共享对象时，number3最后的值为15，number1的值为5 add number1 = 20 // 定义number为共享对象后，两个子进程每次做加法运算时获得的number的值都为最新的值，所以最后number=20
Array的例子：
[root@web thread_process]# cat multi5.py #!/usr/bin/env python import multiprocessing def func(arr): for i in xrange(len(arr)): arr[i] = -arr[i] if __name__ == '__main__': arr = multiprocessing.Array('i', range(10)) p = multiprocessing.Process(target=func, args=(arr,)) print type(arr[:]) print arr[:] p.start() p.join() //必须阻塞主进程，否则主进程退出了，子进程也跟着退出，func函数没有执行，arr[:]没有任何改变 print arr[:] [root@web thread_process]# python multi5.py <type 'list'> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]