Question

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What do I use for a max-heap implementation in Python?

I am trying to implement in some way the heapq of python but for a max-heap. A solution is using the (-1) and multiple with numbers of the queue but that doesn’t help me as I need to store urls in the heap. So i want a max heapq where i can pop the largest value.

Answer 1

Wrap the objects in a reverse-comparing wrapper:

import functools

@functools.total_ordering
class ReverseCompare(object):
    def __init__(self, obj):
        self.obj = obj
    def __eq__(self, other):
        return isinstance(other, ReverseCompare) and self.obj == other.obj
    def __le__(self, other):
        return isinstance(other, ReverseCompare) and self.obj >= other.obj
    def __str__(self):
        return str(self.obj)
    def __repr__(self):
        return '%s(%r)' % (self.__class__.__name__, self.obj)

Usage:

import heapq
letters = 'axuebizjmf'
heap = map(ReverseCompare, letters)
heapq.heapify(heap)
print heapq.heappop(heap) # prints z