#锁
import os
import time
import random
from multiprocessing import Lock # 锁
from multiprocessing import Process
def work(n,lock):
lock.acquire()
print('%s: %s is running' %(n,os.getpid()))
#在这里,同一进程的running和done肯定是紧挨的,
#因为只有一把锁,
time.sleep(random.random())
print('%s:%s is done' %(n,os.getpid()))
lock.release()
if __name__ == '__main__':
lock = Lock()
for i in range(10):
p=Process(target=work,args=(i,lock))
p.start()
#锁之购票例子
import json
import time
import random
from multiprocessing import Process, Lock
def check_ticket(i):
with open('ticket') as f: #仅仅查看,不需要加锁,
ticket_count = json.load(f)
print('person%s查询当前余票 ：' % i, ticket_count['count'])
def buy_ticket(i, lock):
check_ticket(i)
lock.acquire() #如果不能获取锁,代表当前票被占用着,
with open('ticket') as f:
ticket_count = json.load(f)
time.sleep(random.random())
if ticket_count['count'] > 0:
print('person%s购票成功' % i)
ticket_count['count'] -= 1
else:
print('余票不足，person%s购票失败' % i) #其实可以把下面的更改优化到上面,因为这里不涉及更改
time.sleep(random.random())
with open('ticket', 'w') as f:
json.dump(ticket_count, f)
#购票成功,需要把数据更新回文件,并释放保护锁,
lock.release()
if __name__ == '__main__':
lock = Lock()
for i in range(10):
Process(target=buy_ticket, args=[i, lock]).start()
#你能看到这里,我暂且认为你对锁的理解OK,
#锁,锁定的是一个资源
#而信号量,锁定的是一类资源,即可能有好几个这类资源,可以理解为锁+计数器
# KTV 4个房子
import time
import random
from multiprocessing import Process,Semaphore
def ktv(i,sem):
sem.acquire() #若计数器大于0,计数器-1;否则阻塞.
print('person %s 进来唱歌了'%i)
time.sleep(random.randint(1,5))
print('person %s 从ktv出去了'%i)
sem.release() #计数器+1
if __name__ == '__main__':
sem = Semaphore(4)
for i in range(10):
Process(target=ktv,args=(i,sem)).start()
#你是否有这样一个疑问?
#锁和Event有什么区别??
#锁,锁定的是一段资源,
#Event,是通过事件触发,去激活某个被阻塞的状态,
import time
import random
from multiprocessing import Process,Event
def car(i,e):
if not e.is_set():
print('car%s正在等待'%i)
e.wait() #绿灯就直接过,红灯的话就阻塞等待,
print('car%s通过路口'%i)
def traffic_light(e): #专门负责改变红绿灯状态,
print('\033[1;31m红灯亮\033[0m')
# 事件在创立之初的状态是False，相当于我程序中的红灯
time.sleep(2) # 红灯亮2s
while True:
if not e.is_set(): # False
print('\033[1;32m绿灯亮\033[0m')
e.set()
elif e.is_set():
print('\033[1;31m红灯亮\033[0m')
e.clear()
time.sleep(2)
if __name__ == '__main__':
e = Event()
Process(target=traffic_light,args=[e,]).start()
for i in range(50):
time.sleep(random.randrange(0,5,2))
Process(target=car,args=[i,e]).start()
#import queue,这个队列,仅仅是数据结构,不能进行进程间通信
#from multiprocessing import Queue,这个队列能维护一个先进先出的秩序 ,也能进行IPC
import time
import random
from multiprocessing import Process,Queue
def producer(q):
for i in range(10):
time.sleep(random.random())
q.put('包子%s'%i)
print('\033[1;31m生产了包子%s\033[0m'%i)
def consumer(q):
for i in range(5):
food = q.get() #如果get不到,就会一直阻塞在这里,直到有put.
print(food)
print('\033[1;32m消费了%s\033[0m' %food)
time.sleep(random.uniform(1,2))
if __name__ == '__main__':
q = Queue()
p1 = Process(target=producer,args=[q]) #生产包子进程
p2 = Process(target=consumer,args=[q]) #消费包子进程
p3 = Process(target=consumer,args=[q]) #消费包子进程
p1.start()
p2.start()
p3.start()
