python进程间通信Queue工作过程详解

import multiprocessing

q = multiprocessing.Queue(3) # 初始化的Queue对象，最多能put三条消息
q.put("消息1")
q.put("消息2")
print(q.full())
q.put("消息3")
print(q.full())

# 因为消息列队已满下面的try都会抛出异常，第一个try会等待2秒后再抛出异常，第二个Try会立刻抛出异常
try:
    q.put("消息4", True, 2)
except:
    print("消息已满，现有的消息为%d" % (q.qsize()))

try:
    q.put_nowait("消息4")
except:
    print("消息已满，现有的消息为%d" % (q.qsize()))

# 推荐的方式，先判断消息列队是否已满，再写入
if not q.full():
    q.put_nowait("消息4")

# 读取消息时，先判断消息列队是否为空，再读取
if not q.empty():
    for i in range(q.qsize()):
        print(q.get_nowait())

False
True
消息已满，现有的消息为3
消息已满，现有的消息为3
消息1
消息2
消息3

import multiprocessing
import time
import random


def write(q):
    """忘队列中写入数据"""
    for value in "ABCD":
        print("Put %s to queue" % (value))
        q.put(value)
        time.sleep(random.random())


def read(q):
    """读取队列中的数据"""
    while True:
        if not q.empty():
            value = q.get(True)
            print("Get %s from queue" % (value))
            time.sleep(random.random())
        else:
            break


if __name__ == "__main__":

    q = multiprocessing.Queue()

    pw = multiprocessing.Process(target=write, args=(q,))
    pr = multiprocessing.Process(target=read, args=(q,))

    pw.start()
    pw.join()

    pr.start()
    pr.join()
  
    print('')
    print('所有数据都写入并且读完')

Put A to queue
Put B to queue
Put C to queue
Put D to queue
Get A from queue
Get B from queue
Get C from queue
Get D from queue

所有数据都写入并且读完