1.5 heapq实现一个优先级队列

import heapq
class PriorityQueue:
    def __init__(self):
        self._queue = []
        self._index = 0
    def push(self, item, priority):
        # priority越大表示元素优先级越高，-priority就越小，因此越能优先pop
        heapq.heappush(self._queue, (-priority, self._index, item))
        self._index += 1
    def pop(self):
        # 返回heap中最小的元素
        return heapq.heappop(self._queue)[-1]
class Item:
    def __init__(self, name):
        self.name = name
    def __repr__(self):
        return f"Item({self.name})"
# 观察实际效果
q = PriorityQueue()
q.push(Item("foo"), 1)  # 优先级与元素4相同，但index小于元素4，因此优先pop
q.push(Item("bar"), 5)  # 优先级最高
q.push(Item("spam"), 4)  # 优先级次之
q.push(Item("grok"), 1)
q.pop()  # Item('bar')
q.pop()  # Item('spam')
q.pop()  # Item('foo')