基于event 实现的线程安全的优先队列(python实现)

event 事件是个很不错的线程同步，以及线程通信的机制，在python的许多源代码中都基于event实现了很多的线程安全，支持并发，线程通信的库

对于优先队列的堆实现，请看《python下实现二叉堆以及堆排序》, python的event请看<python lock, semaphore, event实现线程同步>, 其实主要注意event几个方法的用法, 以及多线程访问下的程序的逻辑顺序, 在相关代码段放好event的几个方法就好了。自己去理解下, 不难。看下源码吧：

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._event = threading.Event()

    def push(self, item, priority):
        if len(self._queue) != 0:
            self._event.clear()
        while not self._event.is_set():
            self._event.set()
            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._event.set()

    def pop(self):
        if len(self._queue) != 0:
            self._event.set()
        while self._event.is_set():
            self._event.wait()
            x = heapq.heappop(self._queue)[-1]  # 逆序输出
            self._event.clear()
            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()