基于condition 实现的线程安全的优先队列(python实现)

import heapq
import threading
# import time


class Item:
    def __init__(self, name):
        self.name = name

    def __repr__(self):
        return ‘Item({!r})‘.format(self.name)


class PriorityQueue:
    def __init__(self):
        self._queue = []
        self._index = 0
        self.mutex = threading.Lock()
        self.cond = threading.Condition()

    def push(self, item, priority):
        self.cond.acquire()
        heapq.heappush(self._queue, (-priority, self._index, item))  # 存入一个三元组, 默认构造的是小顶堆
        self._index += 1
        self.cond.notify()  # 唤醒一个挂起的线程
        self.cond.release()

    def pop(self):
        self.cond.acquire()
        if len(self._queue) == 0:  # 当队列中数据的数量为0 的时候, 阻塞线程, 要实现线程安全的容器, 其实不难, 了解相关同步原语的机制, 设计好程序执行时的逻辑顺序(在哪些地方阻塞, 哪些地方唤醒)
            self.cond.wait()  # wait方法释放内部所占用的锁, 同时线程被挂起, 知道接收到通知或超时, 当线程被唤醒并重新占用锁, 程序继续执行下去
        else:
            x = heapq.heappop(self._queue)[-1]  # 逆序输出
            self.cond.release()
            return x


def test1(p, item, index):
    for i in range(3):
        p.push(Item(item), index)


def test2(p):
    for i in range(3):
        print(p.pop())


if __name__ == ‘__main__‘:
    p = PriorityQueue()

    t1 = threading.Thread(target=test1, args=(p, ‘foo‘, 1))
    t3 = threading.Thread(target=test1, args=(p, ‘bar‘, 2))
    t4 = threading.Thread(target=test1, args=(p, ‘Ryan‘, 28))

    t2 = threading.Thread(target=test2, args=(p,))
    t5 = threading.Thread(target=test2, args=(p,))
    t6 = threading.Thread(target=test2, args=(p,))

    t1.start()
    t2.start()

    t1.join()
    t2.join()

    t3.start()
    t5.start()

    t3.join()
    t5.join()

    t4.start()
    t6.start()

    t4.join()
    t6.join()