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pythonmin-heapmax-heap

Pop max value from a heapq python, Is there a max-heap in Python?


Possible Duplicate:
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.


Solution

  • 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