#并发运行,效率高,但竞争同一打印终端,带来了打印错乱
from multiprocessing import Process
import os,time
def work():
print('%s is running' %os.getpid())
time.sleep(2)
print('%s is done' %os.getpid())
if __name__ == '__main__':
for i in range(3):
p=Process(target=work)
p.start()
#由并发变成了串行,牺牲了运行效率,但避免了竞争
from multiprocessing import Process,Lock
import os,time
def work(lock):
lock.acquire() #加锁
print('%s is running' %os.getpid())
time.sleep(2)
print('%s is done' %os.getpid())
lock.release() #释放锁
if __name__ == '__main__':
lock=Lock()
for i in range(3):
p=Process(target=work,args=(lock,))
p.start()
二 模拟抢票练习
多个进程共享同一文件，我们可以把文件当数据库，用多个进程模拟多个人执行抢票任务
#文件db.txt的内容为：{"count":1}
#注意一定要用双引号，不然json无法识别
from multiprocessing import Process
import time,json
def search(name):
dic=json.load(open('db.txt'))
time.sleep(1)
print('\033[43m%s 查到剩余票数%s\033[0m' %(name,dic['count']))
def get(name):
dic=json.load(open('db.txt'))
time.sleep(1) #模拟读数据的网络延迟
if dic['count'] >0:
dic['count']-=1
time.sleep(1) #模拟写数据的网络延迟
json.dump(dic,open('db.txt','w'))
print('\033[46m%s 购票成功\033[0m' %name)
def task(name):
search(name)
get(name)
if __name__ == '__main__':
for i in range(10): #模拟并发10个客户端抢票
name='<路人%s>' %i
p=Process(target=task,args=(name,))
p.start()