According to the example from the documentation, you can use tuples, and it will sort by the first element of the tuple:
>>> h = []
>>> heappush(h, (5, 'write code'))
>>> heappush(h, (7, 'release product'))
>>> heappush(h, (1, 'write spec'))
>>> heappush(h, (3, 'create tests'))
>>> heappop(h)
(1, 'write spec')
So if you don't want to (or can't?) do a __cmp__ method, you can manually extract your sorting key at push time.
Note that if the first elements in a pair of tuples are equal, further elements will be compared. If this is not what you want, you need to ensure that each first element is unique.
Answer from Jander on Stack OverflowAccording to the example from the documentation, you can use tuples, and it will sort by the first element of the tuple:
>>> h = []
>>> heappush(h, (5, 'write code'))
>>> heappush(h, (7, 'release product'))
>>> heappush(h, (1, 'write spec'))
>>> heappush(h, (3, 'create tests'))
>>> heappop(h)
(1, 'write spec')
So if you don't want to (or can't?) do a __cmp__ method, you can manually extract your sorting key at push time.
Note that if the first elements in a pair of tuples are equal, further elements will be compared. If this is not what you want, you need to ensure that each first element is unique.
heapq sorts objects the same way list.sort does, so just define a method __cmp__() within your class definition, which will compare itself to another instance of the same class:
def __cmp__(self, other):
return cmp(self.intAttribute, other.intAttribute)
Works in Python 2.x.
In 3.x use:
def __lt__(self, other):
return self.intAttribute < other.intAttribute
I've saw that when setting tuple item as heap element, it would get the first value while popping minimum values from heap.
heap = [(1, 10), (2, 99)]
For the above heap, it's obvious that it would pop the element (1, 10) first, since first elemnt of tuple 1 < 2
However, for those tuple elements where first element is same
heap = [(1, 10), (1, 99)]
I've tested some cases, heap would drop the element (1, 10) first, looks like it compares the second element when first element is same for multiples.
Is that the correct logic that heap would compare following values while first element is the same for tuples?