How to make heapq evaluate the heap off of a specific attribute?

Question

I wish to hold a heap of objects, not just numbers. They will have an integer attribute in them that the heap can sort by. The easiest way to use heaps in python is heapq,

Answer 1

According to the Official Document, a solution to this is to store entries as tuples (please take a look at Section 8.4.1 and 8.4.2).

For example, your object is something like this in tuple's format (key, value_1, value_2)

When you put the objects (i.e. tuples) into heap, it will take the first attribute in the object (in this case is key) to compare. If a tie happens, the heap will use the next attribute (i.e. value_1) and so on.

For example:

import heapq

heap = []
heapq.heappush(heap, (0,'one', 1))
heapq.heappush(heap, (1,'two', 11))
heapq.heappush(heap, (1, 'two', 2))
heapq.heappush(heap, (1, 'one', 3))
heapq.heappush(heap, (1,'two', 3))
heapq.heappush(heap, (1,'one', 4))
heapq.heappush(heap, (1,'two', 5))
heapq.heappush(heap, (1,'one', 1))

show_tree(heap)

Output:

                                      (0, 'one', 1)                                       
                (1, 'one', 1)                                (1, 'one', 4)                
    (1, 'one', 3)         (1, 'two', 3)         (1, 'two', 2)         (1, 'two', 5)     
(1, 'two', 11)

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About pretty print a heap in python (updated the link): show_tree()