多进程 - 队列

multiprocessing.Queue

• q = multiprocessing.Queue()
• q.put(x) # 向队列中放入一个值
• q.get() # 从队列中取一个值
• q.empty() # 判断队列是否为空
• q.full() # 判断队列是否满了
• q.get_nowait() # 从队列中取值，如果队列为空，则抛出异常。普通get()方法为空时堵塞
• q.qsize() # 求取队列长度

生产者消费者模型

用来解决数据供需的平衡问题

• 生产者 -- 进程
• 消费者 -- 进程

import multiprocessing
import time
import random


def consumer(q, name):
    while True:
        food = q.get()
        if food is None:
            print("%s 拿到一个空" % name)
            break
        print("\033[31m%s 消费了 %s\033[0m" %(name, food))
        time.sleep(random.randint(1, 3))


def producer(name, food, q):
    for i in range(10):
        f = "%s生产的 %s %s" % (name, food, i)
        print(f)
        q.put(f)
        time.sleep(1)


if __name__ == "__main__":
    q = multiprocessing.Queue(20)
    p = multiprocessing.Process(target=producer, args=("Sun", "包子", q))
    p.start()
    p2 = multiprocessing.Process(target=producer, args=("Wang", "泔水", q))
    p2.start()
    c1 = multiprocessing.Process(target=consumer, args=(q, "1号"))
    c1.start()
    c2 = multiprocessing.Process(target=consumer, args=(q, "2号"))
    c2.start()
    p.join()
    p2.join()
    q.put(None)
    q.put(None)

JoinableQueue

使用阻塞方式等待队列空闲后退出

import multiprocessing
import time
import random

def consumer(q, name):
    while True:
        food = q.get()
        print("\033[31m%s 消费了 %s\033[0m" %(name, food))
        time.sleep(random.randint(1, 3))
        q.task_done()


def producer(name, food, q):
    for i in range(10):
        f = "%s生产的 %s %s" % (name, food, i)
        print(f)
        q.put(f)
        time.sleep(1)
    q.join()


if __name__ == "__main__":
    q = multiprocessing.JoinableQueue(20)
    p1 = multiprocessing.Process(target=producer, args=("Sun", "包子", q))
    p1.start()
    p2 = multiprocessing.Process(target=producer, args=("Wang", "泔水", q))
    p2.start()
    c1 = multiprocessing.Process(target=consumer, args=(q, "1号"))
    c2 = multiprocessing.Process(target=consumer, args=(q, "2号"))

    c1.daemon = True
    c2.daemon = True

    c1.start()
    c2.start()

    p1.join()
    p2.join()