Python--day41--线程锁

1,死锁

死锁代码示例：

 1 import time
 2 from threading import Lock, Thread
 3 
 4 noodle_lock = Lock()
 5 fork_lock = Lock()
 6 
 7 def eat1(name):
 8     noodle_lock.acquire()
 9     print('%s拿到面了'%name)
10     fork_lock.acquire()
11     print('%s拿到叉子了'%name)
12     print('%s吃面'%name)
13     fork_lock.release()
14     noodle_lock.release()
15 
16 def eat2(name):
17     fork_lock.acquire()
18     print('%s拿到叉子了' % name)
19     time.sleep(1)
20     noodle_lock.acquire()
21     print('%s拿到面了'%name)
22     print('%s吃面'%name)
23     noodle_lock.release()
24     fork_lock.release()
25 
26 Thread(target=eat1,args=('alex',)).start()
27 Thread(target=eat2,args=('Egon',)).start()
28 Thread(target=eat1,args=('bossjin',)).start()
29 Thread(target=eat1,args=('nezha',)).start()

运行结果：

2,线程锁只能保证同一时间只有一个线程取n值，并不能保证数据安全

3,加锁保证了n不会被多个线程操纵；加锁保证数据安全

 1 import time
 2 from threading import Lock,Thread
 3 
 4 def func(lock):
 5     global n
 6     #加锁保证了n不会被多个线程操纵
 7     #获取锁的钥匙，加锁
 8     lock.acquire()
 9     temp = n
10     time.sleep(0.2)#睡眠0.2s
11     n = temp -1
12     #释放锁
13     lock.release()
14 
15 n = 10
16 t_lst = []
17 lock = Lock()
18 for i in range(10):
19     t = Thread(target=func,args=(lock,))
20     t.start()
21     t_lst.append(t)
22 
23 
24 for t in t_lst:t.join()
25 print(n)

运行结果：