互斥锁
多线程下操作同一数据
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| import time
from threading import Thread
n = 100
def task():
global n
temp = n
time.sleep(0.1)
n = temp-1
if __name__ == '__main__':
arr = []
for i in range(100):
t = Thread(target=task)
arr.append(t)
t.start()
# 保证所有线程都执行完毕
for t in arr:
t.join()
print('主',n)
执行结果：
主 99
|
此时就不安全了，100个线程都操作了但是数据还是99
互斥锁的应用
牺牲效率来保证数据的安全——将并行变成串行
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| import time
from threading import Thread,Lock
n = 100
def task(mutex):
global n
mutex.acquire()
temp = n
time.sleep(0.1)
n = temp-1
mutex.release()
if __name__ == '__main__':
mutex=Lock()
arr = []
for i in range(100):
t = Thread(target=task,args=(mutex,))
arr.append(t)
t.start()
# 保证所有线程都执行完毕
for t in arr:
t.join()
print('主',n)
|