multiple producers and multiple consumers working on the same queue

producer-consumer.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-
# slightly modified from https://stackoverflow.com/questions/53778588/two-condition-variables-attached-to-the-same-lock-different-behaviors-in-python
# 也請見 「概念性、宏觀視野的程序/執行緒同步機制總覽」
# https://newtoypia.blogspot.com/2017/12/synchronization.html

# Note: pip3 install colored

from threading import Thread, Lock, Condition
import time
from random import random, randint
import colored
from colored import stylize

queue = []
CAPACITY = 3

qlock = Lock()
item_ok = Condition(qlock)
space_ok = Condition(qlock)

class ProducerThread(Thread):
    def run(self):
        global queue
        mycolor = self.name
        while True:
            qlock.acquire()
            while len(queue) >= CAPACITY:
                print(stylize('queue is full, stop producing', colored.fg(mycolor)))
                space_ok.wait()
                if len(queue) >= CAPACITY:
                    print(stylize('oops, someone filled the space before me', colored.fg(mycolor)))
            item = chr(ord('A')+randint(0,25))
            print(stylize('['+' '.join(queue)+'] <= '+item, colored.fg( mycolor)))
            queue.append(item)
            item_ok.notify()
            qlock.release()
            time.sleep((random()+1)*1.5)


class ConsumerThread(Thread):
    def run(self):
        global queue
        mycolor = self.name
        while True:
            qlock.acquire()
            while not queue:
                print(stylize('queue is empty, stop consuming', colored.fg(mycolor)))
                item_ok.wait()
                if not queue:
                    print(stylize('oops, someone consumed the food before me', colored.fg(mycolor)))
            item = queue.pop(0)
            print(stylize(item+' <= ['+' '.join(queue)+']', colored.fg( mycolor)))
            space_ok.notify()
            qlock.release()
            time.sleep((random()+1)*1.5)

ProducerThread(name='red', daemon=True).start()
ProducerThread(name='green', daemon=True).start()
ProducerThread(name='blue', daemon=True).start()
ConsumerThread(name='cyan', daemon=True).start()
ConsumerThread(name='magenta', daemon=True).start()
ConsumerThread(name='yellow', daemon=True).start()

try:
    while True:
        time.sleep(3)
except KeyboardInterrupt:
    print("Exiting")

多個 producers 多個 consumers 的 python 程式。 注意： 本程式要用 python3 執行。 執行前請先以 pip3 install colored 安裝相依套件。 詳見 概念性、宏觀視野的程序/執行緒同步機制總覽。 感謝 stackoverflow 網友 Felix 的協助。