Spiders = []
    t = SpiderThread( "aaa" ,text ) 
    Spiders.append( t ) 
    t = SpiderThread( "bbb",text )
    Spiders.append( t ) 
    t = SpiderThread( "ccc",text )
    Spiders.append( t ) 
    t = SpiderThread( "ddd" ,text)
    Spiders.append( t )
        
    for t in Spiders:
        t.start()  #同时开始4 个线程
            
    while threading.activeCount() > 1:  等待线程结束
        # sets the Event's flag to true -- awaken all waiting vehicles
        for t in Spiders:
            if t.busy == False: #这表明线程执行完毕
                file=open("xml%s-%s.html" %(t.name, t.partno),"w")
                file.write(t.htmlcode)
                file.close()
                print t.name + t.htmlcode
                t.join(0) #结束线程


############## 线程  SpiderThread 代码如下 ################
class SpiderThread( threading.Thread ):
    """Class representing a motor vehicle at an intersection"""

    def __init__( self, threadName,keyword ):
        """Initializes thread"""

        threading.Thread.__init__( self, name = threadName )
        self.keyword = keyword
        self.name = threadName
        self.htmlcode = ""
        self.busy = True
        
    def run( self ):
        self.htmlcode = self.getHtmlCode(self.name, self.keyword )
        self.busy = False

    def getHtmlCode (self, webname, keyword):
        """ 这里面就是调用urllib 去访问网站，并返回HTML源代码的一个函数"""
        ...略