Is there any way exists that can do the java queue priority comparator.comparingInt method in Python?
I want the node which has a higher priority come to the front of the queue.
edited: for example:
class node: def __init__(self, label, priority): self.label = label self.priority = priority node1 = node('a', 3) node2 = node('b',2) node3 = node('c', 1) nodes in queue comes like this==> (node1,node2,node3) 2 Answers
As Albin states, you'll need to use the heapq module (unless you want to write your own heap implementation from scratch). One very important thing to note is that this library gives only an implementation of a min-heap, rather than a max-heap.
To write a comparator for a custom object, you'll need to override the __lt__ function (the function that's called when the < operator is used). So your node class would look like this:
class node: nodes = dict() def __init__(self, label, priority): self.label = label self.priority = priority def __lt__(self, other): # Note that we've reversed the operands here, since we want a max-heap. return other.priority < self.priority Then, we can make a heap as follows:
import heapq heap = [] node1 = node('a', 3) node2 = node('b', 2) node3 = node('c', 1) heapq.heappush(heap, node1) heapq.heappush(heap, node2) heapq.heappush(heap, node3) # Should print 'a', 'b', 'c' in that order. for i in range(3): print(heapq.heappop(heap).label) You should look closer on this documentation regarding priority queues (heapq for python3):
It refers to the priority queue and also have basic examples of sorting based on a value inside a tuple.
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