多线程 -- 同步锁

import time
import threading

def addNum():
    #在每个线程中都获取这个全局变量
    global num

    temp = num
    time.sleep(0.1)
    #对此公共变量进行-1操作
    num = temp-1

#设定一个共享变量
num = 100
thread_list = []
for i in range(100):
    t = threading.Thread(target=addNum)
    t.start()
    thread_list.append(t)

#等待所有线程执行完毕
for t in thread_list:
    t.join()

print(‘final num:‘, num )

输出：
99

import time
import threading

def addNum():
    global num

    lock.acquire()
    temp = num
    time.sleep(0.1)
    num = temp-1
    lock.release()

num = 100
thread_list = []
lock = threading.Lock()

for i in range(100):
    t = threading.Thread(target=addNum)
    t.start()
    thread_list.append(t)

for t in thread_list:
    t.join()

print(‘final num:‘, num )

输出：
0