python：生产者与消费者模型

Posted 2020-10-23 kakawith

1，生产者与消费者模型的矛盾在于数据供需的不平衡

import time
import random
from multiprocessing import Queue
from multiprocessing import Process
def producer(q,food):
    for i in range(5):
        q.put(‘%s-%s‘%(food,i))
        print(‘生产了%s‘%food)
        time.sleep(random.random())
    q.put(None)
    q.put(None)
    q.put(None)#有三个消费者因此需要三个信号

def consumer(q,name):
    while True:
        food = q.get()
        if food == None:break
        print(‘%s 吃了 %s‘%(name,food))

if __name__ == ‘__main__‘:
    q = Queue()
    p1 = Process(target=producer,args=(q,‘菠萝蜜干‘))
    p1.start()
    p2 = Process(target=producer, args=(q, ‘酸奶‘))
    p2.start()
    c1 = Process(target=consumer, args=(q, ‘Rabbit‘))
    c1.start()
    c2 = Process(target=consumer, args=(q, ‘OrangeCat‘))
    c2.start()
    c3 = Process(target=consumer, args=(q, ‘CuiHua‘))
    c3.start()

生产者消费者模型
    1.消费者要处理多少数据是不确定的
    2.所以只能用while循环来处理数据 ，但是while循环无法结束
    3.需要生产者发送信号
    4.有多少个消费者 就需要发送多少个信号
    5.但是发送的信号数量需要根据 生产者和消费者的数量进行计算，所以非常不方便
2，JoinableQueue

import time
import random
from multiprocessing import Process
from multiprocessing import JoinableQueue

def producer(q,food):
    for i in range(5):
        q.put(‘%s-%s‘%(food,i))
        print(‘生产了%s‘%food)
        time.sleep(random.random())
    q.join()  # 等待消费者把所有的数据都处理完

def consumer(q,name):
    while True:
        food = q.get()   # 生产者不生产还是生产的慢
        print(‘%s 吃了 %s‘%(name,food))
        q.task_done()#JoinableQueue内部自带计数功能，每执行一次task_done，计数减一。

if __name__ == ‘__main__‘:
    q = JoinableQueue()
    p1 = Process(target=producer,args=(q,‘炒河粉‘))
    p1.start()
    p2 = Process(target=producer, args=(q, ‘草莓‘))
    p2.start()
    c1 = Process(target=consumer, args=(q, ‘Rabbit‘))
    c1.daemon = True
    c1.start()
    c2 = Process(target=consumer, args=(q, ‘Orange_Cat‘))
    c2.daemon = True
    c2.start()
    c3 = Process(target=consumer, args=(q, ‘Teddy‘))
    c3.daemon = True
    c3.start()

    p1.join()  # 等待p1执行完毕
    p2.join()  # 等待p2执行完毕

生产者生产的数据全部被消费 —— 生产者进程结束 —— 主进程代码执行结束 —— 消费者守护进程结束