python 多进程编程

转载自：http://www.cnblogs.com/alan-babyblog/p/5339501.html

创建进程的类：Process([group [, target [, name [, args [, kwargs]]]]])，target表示调用对象，args表示调用对象的位置参数元组。kwargs表示调用对象的字典。name为别名。group实质上不使用。
方法：is_alive()、join([timeout])、run()、start()、terminate()。其中，Process以start()启动某个进程。

属性：authkey、daemon（要通过start()设置）、exitcode(进程在运行时为None、如果为–N，表示被信号N结束）、name、pid。其中daemon是父进程终止后自动终止，且自己不能产生新进程，必须在start()之前设置。

例1.1：创建函数并将其作为单个进程

#!usr/bin/python#-*-coding:utf-8-*-import multiprocessingimport time def worker(interval):    n = 5    while n > 0:        print("The time is {0}".format(time.ctime()))        time.sleep(interval)        n -= 1 if __name__ == "__main__":    p = multiprocessing.Process(target = worker, args = (3,))    p.start()    print "p.pid:", p.pid    print "p.name:", p.name    print "p.is_alive:", p.is_alive()

p.pid: 8736p.name: Process-1p.is_alive: TrueThe time is Tue Apr 21 20:55:12 2015The time is Tue Apr 21 20:55:15 2015The time is Tue Apr 21 20:55:18 2015The time is Tue Apr 21 20:55:21 2015The time is Tue Apr 21 20:55:24 2015

例1.2：创建函数并将其作为多个进程

#!usr/bin/python#-*-coding:utf-8-*-import multiprocessingimport time def worker_1(interval):    print "worker_1"    time.sleep(interval)    print "end worker_1" def worker_2(interval):    print "worker_2"    time.sleep(interval)    print "end worker_2" def worker_3(interval):    print "worker_3"    time.sleep(interval)    print "end worker_3" if __name__ == "__main__":    p1 = multiprocessing.Process(target = worker_1, args = (2,))    p2 = multiprocessing.Process(target = worker_2, args = (3,))    p3 = multiprocessing.Process(target = worker_3, args = (4,))     p1.start()    p2.start()    p3.start()     print("The number of CPU is:" + str(multiprocessing.cpu_count()))    for p in multiprocessing.active_children():        print("child   p.name:" + p.name + "\tp.id" + str(p.pid))    print "END!!!!!!!!!!!!!!!!!"

The number of CPU is:4child   p.name:Process-3    p.id7992child   p.name:Process-2    p.id4204child   p.name:Process-1    p.id6380END!!!!!!!!!!!!!!!!!worker_1worker_3worker_2end worker_1end worker_2end worker_3

例1.3将进程定义为新类，该类继承multiprocessing.Process

#!/usr/bin/python# -*- coding: utf-8 -*-import multiprocessingimport time class ClockProcess(multiprocessing.Process):    def __init__(self, interval):        multiprocessing.Process.__init__(self)        self.interval = interval     def run(self):        n = 5        while n > 0:            print("the time is {0}".format(time.ctime()))            time.sleep(self.interval)            n -= 1 if __name__ == '__main__':    p = ClockProcess(3)    p.start()

the time is Tue Apr 21 20:31:30 2015the time is Tue Apr 21 20:31:33 2015the time is Tue Apr 21 20:31:36 2015the time is Tue Apr 21 20:31:39 2015the time is Tue Apr 21 20:31:42 2015

例1.4：daemon程序对比结果

#1.4-1 不加daemon属性

#!/usr/bin/python# -*- coding: utf-8 -*-import multiprocessingimport time def worker(interval):    print("work start:{0}".format(time.ctime()));    time.sleep(interval)    print("work end:{0}".format(time.ctime())); if __name__ == "__main__":    p = multiprocessing.Process(target = worker, args = (3,))    p.start()    print "end!"

end!work start:Tue Apr 21 21:29:10 2015work end:Tue Apr 21 21:29:13 2015

#1.4-2 加上daemon属性

#!/usr/bin/python# -*- coding: utf-8 -*-import multiprocessingimport time def worker(interval):    print("work start:{0}".format(time.ctime()));    time.sleep(interval)    print("work end:{0}".format(time.ctime())); if __name__ == "__main__":    p = multiprocessing.Process(target = worker, args = (3,))    p.daemon = True    p.start()    print "end!"

end!

注：因子进程设置了daemon属性，主进程结束，它们就随着结束了。

#1.4-3 设置daemon执行完结束的方法

#!/usr/bin/python# -*- coding: utf-8 -*-import multiprocessingimport time def worker(interval):    print("work start:{0}".format(time.ctime()));    time.sleep(interval)    print("work end:{0}".format(time.ctime())); if __name__ == "__main__":    p = multiprocessing.Process(target = worker, args = (3,))    p.daemon = True    p.start()    p.join()    print "end!"

work start:Tue Apr 21 22:16:32 2015work end:Tue Apr 21 22:16:35 2015end!