如何开启守护线程

#多个线程下开守护线程
from threading import Thread
import time
def sayhi():
    print(123)
    time.sleep(1)
    print('end123')
def bar():
    print(456)
    time.sleep(3)
    print('end456')
if __name__ == '__main__':
    t1 = Thread(target=sayhi)
    t2 = Thread(target=bar)
    t1.setDaemon(True) #我是设置守护线程的，必须设置在起动线程之前
    t1.daemon = True #我是设置守护线程的，必须设置在起动线程之前
    t1.start()
    t2.start()
    print('老代吃%s'%'鸟屎是主线程')
#单个线程下开守护线程
from threading import Thread
import time
def task(name):
    time.sleep(2)
    print('%s吃屎'%name)
if __name__ == '__main__':
    t = Thread(target=task, args=('老代', ))
    t.setDaemon(True)   #我是设置守护线程的，必须设置在起动线程之前
    t.start()
    print('主 哈哈哈哈')