Python Priority Queue checking to see if item exists without looping

Question

import heapq
class PriorityQueue:

    def __init__(self):
        self.heap = []

    def push(self, item, priority):
        pair = (priority,item)
        heapq.heappush(self.heap,pair)

    def pop(self):
       return heapq.heappop(self.heap)

    def isEmpty(self):
        return len(self.heap) == 0

    def clear(self):
        while not (self.isEmpty()):
            self.heap.pop()

    def getHeap(self):
        return self.heap

    def getLeng(self):
        return len(self.heap)

    def exists(self, item):
       return len(list(set(self.heap) & set(item)))

pq = PriorityQueue()
x = "test"
pq.push(x,1)
print pq.exists(x)

it printed 0 when it should print 1 since intersection of a set with x and another set with x should be 1

am i overlooking things?
why is it printing 0 instead of 1?

KillianDS · Accepted Answer · 2013-08-12 07:54:20Z

3

You are pushing tuples of (priority,value) to the heap but want the exist method to work only on values, so you should get a value-only list/iterator out of your heap, something like this:

def exists(self, item):
   return item in (x[1] for x in self.heap)

answered Aug 12, 2013 at 7:54

KillianDS

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