守护线程

from threading import Thread
import time
def sayhi(name):
    time.sleep(2)
    print("%s sat hello" % name)
if __name__=="__main__":
    t=Thread(target=sayhi,args=(‘Ya‘,))
    t.setDaemon(True)
    # t.daemon=True
    t.start()
    print("‘主‘线程")
    print(t.isAlive())

from threading import Thread
import time
def foo():
    print(123)
    time.sleep(1)
    print("end123")
def bar():
    print(456)
    time.sleep(3)
    print("end456")
if __name__ == "__main__":
    t1=Thread(target=foo)
    t2=Thread(target=bar)

    t1.daemon=True
    t1.start()
    t2.start()
    print("---main---")

from threading import Thread,Lock
n=100
import time
def task():
    global n
    mutex.acquire()
    temp=n
    time.sleep(0.1)
    n=temp-1
    mutex.release()
if __name__=="__main__":
    t_l=[]
    mutex=Lock()
    for i in range(100):
        t=Thread(target=task)
        t_l.append(t)
        t.start()
    for t in t_l:
        t.join()
    print("主线程:",n)