Python 之 threading

创建多线程常用的三种方法：

• 创建Thread的实例，传给它一个函数
• 创建Thread的实例，传给它一个可调用的类实例（不推荐）
• 派生Thread的子类，并创建子类的实例（推荐）

创建Thread的实例，传给它一个函数

#!/usr/bin/env python
# coding:utf-8


import threading
from time import ctime, sleep

loops = [4, 2]

def loop(n, sec):
    print 'start loop', n, ' at: ', ctime()
    sleep(sec)
    print 'loop', n, ' done at: ', ctime()
    
def main():
    print 'starting at: ', ctime()
    threads = []
    nloops = range(len(loops))
    
    for i in nloops:
        t = threading.Thread(target=loop, args=(i, loops[i]))
        threads.append(t)
        
    for i in nloops:    # start threads
        threads[i].start()
        
    for i in nloops:    # wait for all threads to finish
        threads[i].join()
        
    print 'all DONE at: ', ctime()
    
if __name__ == '__main__':
    main()

执行结果：

liuqian@ubuntu:~$ python test_threading1.py
starting at:  Wed Jul 20 13:20:06 2016
start loop 0  at:  Wed Jul 20 13:20:06 2016
start loop 1  at:  Wed Jul 20 13:20:06 2016
loop 1  done at:  Wed Jul 20 13:20:08 2016
loop 0  done at:  Wed Jul 20 13:20:10 2016
all DONE at:  Wed Jul 20 13:20:10 2016

【说明】

join([timeout])方法将等待线程结束，或者在提供了超时时间的情况下达到超时时间。对于join()方法而言，其实它根本不需要调用。一旦线程启动，它就会一直执行，直到给定的函数完成后退出。如果主线程还有其他事情要去做，而不是等待这些线程完成（例如其他处理或者等待新的客户端请求），就可以不调用join()。join()只在你需要等待线程完成的时候才是有用的。

创建Thread的实例，传给它一个可调用的类实例

#!/usr/bin/env python
# coding:utf-8


import threading
from time import ctime, sleep

loops = [4,2]

class ThreadFunc(object):
    
    def __init__(self, func, args, name=''):
        self.name = name
        self.func = func
        self.args = args
        
    def __call__(self):
        self.func(*self.args)
        
def loop(n, sec):
    print 'start loop', n, ' at: ', ctime()
    sleep(sec)
    print 'loop', n, ' done at: ', ctime()
    
def main():
    print 'starting at: ', ctime()
    threads = []
    nloops = range(len(loops))
    
    for i in nloops:
        t = threading.Thread(target=ThreadFunc(loop, (i, loops[i]), loop.__name__))
        threads.append(t)
        
    for i in nloops:    # start threads
        threads[i].start()
        
    for i in nloops:    # wait for all threads to finish
        threads[i].join()
        
    print 'all DONE at: ', ctime()
    
if __name__ == '__main__':
    main()

输出与第一个案例一样。

【说明】当创建新线程时，Thread类的代码将调用ThreadFunc对象，此时会调用__cal__()这个特殊方法。

派生Thread的子类，并创建子类的实例（推荐）

#!/usr/bin/env python
# coding:utf-8

import threading
from time import ctime, sleep

loops = [4,2]

class MyThread(threading.Thread):
    
    def __init__(self, func, args, name=''):
        threading.Thread.__init__(self)
        self.name = name
        self.func = func
        self.args = args
        
    def run(self):    # 必须要写
        self.func(*self.args)
        
def loop(n, sec):
    print 'start loop', n, ' at: ', ctime()
    sleep(sec)
    print 'loop', n, ' done at: ', ctime()
    
def main():
    print 'starting at: ', ctime()
    threads = []
    nloops = range(len(loops))
    
    for i in nloops:
        t = MyThread(loop, (i, loops[i]), loop.__name__)
        threads.append(t)
        
    for i in nloops:    # start threads
        threads[i].start()
        
    for i in nloops:    # wait for all threads to finish
        threads[i].join()
        
    print 'all DONE at: ', ctime()
    
if __name__ == '__main__':
    main()