threads

import time
from threading import Thread

class THRD( Thread): 
    def __init__( self):
        Thread.__init__( self)
    def run(self):
        count = 0
        while 1:
            count += 1
            time.sleep(1)
            print( "this is thread ")
            if count > 20:
                print( " thread ends")
                break

p = THRD()
p.start()