code
# 文件db的内容为：{"count":1}
# 注意一定要用双引号，不然json无法识别
# 并发运行，效率高，但竞争写同一文件，数据写入错乱
from multiprocessing import Process,Lock
import time,json,random
def search():
dic=json.load(open('db'))
print('剩余票数%s' %dic['count'])
def get():
dic=json.load(open('db'))
time.sleep(0.1) # 模拟读数据的网络延迟
if dic['count'] >0:
dic['count']-=1
time.sleep(0.2) # 模拟写数据的网络延迟
json.dump(dic,open('db','w'))
print('购票成功')
def task():
search()
get()
if __name__ == '__main__':
for i in range(100): # 模拟并发100个客户端抢票
p=Process(target=task)
p.start()
outputs
macname@MacdeMacBook-Pro py % python3 cccccc.py 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 剩余票数1 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 购票成功 macname@MacdeMacBook-Pro py % cat db {"count": 0}
macname@MacdeMacBook-Pro py %