python中通过类的方式创建线程

import threading
import time

class MyThread(threading.Thread):
    def __init__(self,num):
        threading.Thread.__init__(self)
        self.num=num
    def run(self):# 定义每个线程要运行的函数
        print("running on number:%s"% self.num)
        time.sleep(3)

if __name__=='__main__':
    t1=MyThread(1)
    t2=MyThread(2)
    t1.start()
    t2.start()