python使用Queue实现优先级队列

import Queue

class PriorityQueue(Queue.Queue):
    def _put(self,item):
        data,priority = item
        self._insort_right((priority,data))

    def _get(self):
        return self.queue.pop(0)[1]

    def _insort_right(self,x):
        """Insert item x in list,and keep it sorted assuming a is sorted.

        If x is already in list,insert it to the right of the rightmost x.       
        """
        a = self.queue
        lo = 0        
        hi = len(a)

        while lo < hi:
            mid = (lo+hi)/2
            if x[0] < a[mid][0]: hi = mid
            else: lo = mid+1
        a.insert(lo,x)

def test():
    pq = PriorityQueue()

    pq.put(('b',1))
    pq.put(('a',1))
    pq.put(('c',1))
    pq.put(('z',0))
    pq.put(('d',2))

    while not pq.empty():
        print pq.get(),test() # prints z b a c d