Python多线程详解

1、多线程的理解

多进程和多线程都可以执行多个任务,线程是进程的一部分。线程的特点是线程之间可以共享内存和变量,资源消耗少(不过在Unix环境中,多进程和多线程资源调度消耗差距不明显,Unix调度较快),缺点是线程之间的同步和加锁比较麻烦。

2、Python多线程创建

在Python中,同样可以实现多线程,有两个标准模块thread和threading,不过我们主要使用更高级的threading模块。使用例子:

1234567891011121314151617181920 import threadingimport time def target():    print \’the curent threading  %s is running\’ % threading.current_thread().name    time.sleep(1)    print \’the curent threading  %s is ended\’ % threading.current_thread().name print \’the curent threading  %s is running\’ % threading.current_thread().namet = threading.Thread(target=target) t.start()t.join()print \’the curent threading  %s is ended\’ % threading.current_thread().name 输出:the curent threading  MainThread is runningthe curent threading  Thread1 is runningthe curent threading  Thread1 is endedthe curent threading  MainThread is ended

start是启动线程,join是阻塞当前线程,即使得在当前线程结束时,不会退出。从结果可以看到,主线程直到Thread-1结束之后才结束。
Python中,默认情况下,如果不加join语句,那么主线程不会等到当前线程结束才结束,但却不会立即杀死该线程。如不加join输出如下:

1234 the curent threading  MainThread is runningthe curent threading  Thread1 is running the curent threading  MainThread is endedthe curent threading  Thread1 is ended

但如果为线程实例添加t.setDaemon(True)之后,如果不加join语句,那么当主线程结束之后,会杀死子线程。代码:

123456789101112131415 import threadingimport timedef target():    print \’the curent threading  %s is running\’ % threading.current_thread().name    time.sleep(4)    print \’the curent threading  %s is ended\’ % threading.current_thread().nameprint \’the curent threading  %s is running\’ % threading.current_thread().namet = threading.Thread(target=target)t.setDaemon(True)t.start()t.join()print \’the curent threading  %s is ended\’ % threading.current_thread().name输出如下:the curent threading  MainThread is runningthe curent threading  Thread1 is runningthe curent threading  MainThread is ended

如果加上join,并设置等待时间,就会等待线程一段时间再退出:

1234567891011121314151617181920 import threadingimport timedef target():    print \’the curent threading  %s is running\’ % threading.current_thread().name    time.sleep(4)    print \’the curent threading  %s is ended\’ % threading.current_thread().nameprint \’the curent threading  %s is running\’ % threading.current_thread().namet = threading.Thread(target=target)的一部分。线程的特点是线程之间可以共享内存和变量,资源消耗少(不过在Unix环境中,多进程和多线程资源调度消耗差距不明显,Unix调度较快),缺点是线程之间的同步和加锁比较麻烦。

2、Python多线程创建

在Python中,同样可以实现多线程,有两个标准模块thread和threading,不过我们主要使用更高级的threading模块。使用例子:

1234567891011121314151617181920 import threadingimport time def target():    print \’the curent threading  %s is running\’ % threading.current_thread().name    time.sleep(1)    print \’the curent threading  %s is ended\’ % threading.current_thread().name print \’the curent threading  %s is running\’ % threading.current_thread().namet = threading.Thread(target=target) t.start()t.join()print \’the curent threading  %s is ended\’ % threading.current_thread().name 输出:the curent threading  MainThread is runningthe curent threading  Thread1 is runningthe curent threading  Thread1 is endedthe curent threading  MainThread is ended

start是启动线程,join是阻塞当前线程,即使得在当前线程结束时,不会退出。从结果可以看到,主线程直到Thread-1结束之后才结束。
Python中,默认情况下,如果不加join语句,那么主线程不会等到当前线程结束才结束,但却不会立即杀死该线程。如不加join输出如下:

1234 the curent threading  MainThread is runningthe curent threading  Thread1 is running the curent threading  MainThread is endedthe curent threading  Thread1 is ended

但如果为线程实例添加t.setDaemon(True)之后,如果不加join语句,那么当主线程结束之后,会杀死子线程。代码:

123456789101112131415 import threadingimport timedef target():    print \’the curent threading  %s is running\’ % threading.current_thread().name    time.sleep(4)    print \’the curent threading  %s is ended\’ % threading.current_thread().nameprint \’the curent threading  %s is running\’ % threading.current_thread().namet = threading.Thread(target=target)t.setDaemon(True)t.start()t.join()print \’the curent threading  %s is ended\’ % threading.current_thread().name输出如下:the curent threading  MainThread is runningthe curent threading  Thread1 is runningthe curent threading  MainThread is ended

如果加上join,并设置等待时间,就会等待线程一段时间再退出:

1234567891011121314151617181920 import threadingimport timedef target():    print \’the curent threading  %s is running\’ % threading.current_thread().name    time.sleep(4)    print \’the curent threading  %s is ended\’ % threading.current_thread().nameprint \’the curent threading  %s is running\’ % threading.current_thread().namet = threading.Thread(target=target) class=\”crayon-line\” id=\”crayon-5812b1ece1b8d723394978-9\”>t.setDaemon(True)t.start()t.join(1)输出: