实现优先级队列

import heapq

class PriorityQueue:
    def __init__(self):
        self._queue = []
        self._index = 0

    def push(self, item, priority):
        heapq.heappush(self._queue, (-priority, self._index, item))
        self._index += 1
        
    def pop(self):
        return heapq.heappop(self._queue)[-1]

>>> class Item:
... 　　def __init__(self, name):
... 　　　　self.name = name
... 
... 　　def __repr__(self):
... 　　　　return ‘Item({!r})‘.format(self.name)
... 
>>> q = PriorityQueue()
>>> q.push(Item(‘foo‘), 1)
>>> q.push(Item(‘bar‘), 5)
>>> q.push(Item(‘spam‘), 4)
>>> q.push(Item(‘grok‘), 1)

>>> q.pop()
Item(‘bar‘)
>>> q.pop()
Item(‘spam‘)
>>> q.pop()
Item(‘foo‘)
>>> q.pop()
Item(‘grok‘)

>>> a = Item(‘foo‘)
>>> b = Item(‘bar‘)

>>> a < b 
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unorderable types: Item() < Item()
>>>

>>> a = (1, Item(‘foo‘))
>>> b = (5, Item(‘bar‘))
>>> a < b )
True
>>> c = (1, Item(‘grok‘))
>>> a < c 
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unorderable types: Item() < Item()
>>>

>>> a = (1, 0, Item(‘foo‘))
>>> b = (5, 1, Item(‘bar‘))
>>> c = (1, 2, Item(‘grok‘))
>>> a < b 
True
>>> a < c 
True