python中上双互斥锁的线程执行流程

import threading

def sing():
    print('进入sing -----------------')
    for i in range(3):
        print('进入sing循环 -----------------')
        l1.acquire()
        print('sing上锁 -----------------')
        print('唱歌。。。')
        try:
            print('dance解锁 -----------------')
            l2.release()
            print('dance解锁成功 -----------------')
        except Exception:
            print('sing中dance解锁失败，重新开始循环----------------')
            pass

def dance():
    print('进入dance -----------------')
    for i in range(3):
        print('进入dance循环 -----------------')
        l2.acquire()
        print('dance上锁 -----------------')
        print('跳舞。。。')
        try:
            print('sing解锁 -----------------')
            l1.release()
            print('sing解锁成功 -----------------')
        except Exception:
            print('dance中sing解锁失败，重新开始循环----------------')
            pass

if __name__ == '__main__':
    # sing()
    # dance()
    l1 = threading.Lock()
    print(l1)
    l2 = threading.Lock()
    print(l2)
    t1 = threading.Thread(target=sing)
    t2 = threading.Thread(target=dance)
    print('线程创建完毕--------')
    t1.start()
    print('线程1开始执行------')
    t2.start()
    print('线程2开始执行------')
    t1.join()
    print('线程1守护主线程-----')
    t2.join()
    print('线程2守护主线程-----')