python_锁

import threading

num = 0
lock = threading.Lock()  #申请一把锁
def add():
    global num
    #lock.acquire() #加锁
    #num+=1
    #lock.release() #解锁
    with lock:  #简写，用with会自动帮你加锁，解锁
        num = num + 1

for i in range(20):
    t = threading.Thread(target=add,)
    t.start()
while threading.activeCount() !=1:
    pass

print(num)