python 多线程 入门

python里的多线程，一直用得不是很多。为了最快速的上手，搞明白多线程到底是个什么鬼，写了个简单的例子

#!/usr/bin/env python#coding:utf-8'''Created on 2016年6月3日@author: lei.wang'''import threadingfrom time import ctime,sleepdef music(entertainment):    for i in range(2):        print "Listening to %s. %s" %(entertainment,ctime())        sleep(1)def movie(entertainment):    for i in range(2):        print "Watching the %s. %s" %(entertainment,ctime())        sleep(5)if __name__ == '__main__':    threads = []    thread_music = threading.Thread(target=music,args=(u"暗号",))    threads.append(thread_music)    thread_movie = threading.Thread(target=movie,args=(u"肖圣克救赎",))    threads.append(thread_movie)    for each in threads:        each.setDaemon(True)        each.start()    each.join()    print "all threads end at %s" %(ctime())    

代码运行结果

Listening to 暗号. Fri Jun  3 12:38:12 2016Watching the 肖圣克救赎. Fri Jun  3 12:38:12 2016Listening to 暗号. Fri Jun  3 12:38:13 2016Watching the 肖圣克救赎. Fri Jun  3 12:38:17 2016all threads end at Fri Jun  3 12:38:22 2016

对代码做个简单的分析：
首先创建一个空的threads列表，用来存放线程。然后分别创建线程thread_music与thread_moive。

将Thread中源码构造函数的说明部分抠出来：

class Thread(_Verbose):    """A class that represents a thread of control.    This class can be safely subclassed in a limited fashion.    """    __initialized = False    # Need to store a reference to sys.exc_info for printing    # out exceptions when a thread tries to use a global var. during interp.    # shutdown and thus raises an exception about trying to perform some    # operation on/with a NoneType    __exc_info = _sys.exc_info    # Keep sys.exc_clear too to clear the exception just before    # allowing .join() to return.    __exc_clear = _sys.exc_clear    def __init__(self, group=None, target=None, name=None,                 args=(), kwargs=None, verbose=None):        """This constructor should always be called with keyword arguments. Arguments are:        *group* should be None; reserved for future extension when a ThreadGroup        class is implemented.        *target* is the callable object to be invoked by the run()        method. Defaults to None, meaning nothing is called.        *name* is the thread name. By default, a unique name is constructed of        the form "Thread-N" where N is a small decimal number.        *args* is the argument tuple for the target invocation. Defaults to ().        *kwargs* is a dictionary of keyword arguments for the target        invocation. Defaults to {}.        If a subclass overrides the constructor, it must make sure to invoke        the base class constructor (Thread.__init__()) before doing anything        else to the thread."""

通过源码，很容易看出来
thread_music = threading.Thread(target=music,args=(u"暗号",))
是如何构造一个线程的。

jion()方法放在for循环外边，就是说必须要等for循环里的两个进程都结束以后，才能继续执行主进程。

从代码最后的结果来分析，thread_music与thread_movie是同时开始执行的，music进程sleep1s后执行第二次，而movie进程sleep5s后执行第二次。主进程在两个线程都执行完了以后才执行。