Let’s create a priority queue with 5 elements and check whether the priority queue is empty or not. Heaps are binary trees for which every parent node has a value less than or equal to any of its children. This solution may only work starting with Python 3.7. Priorityqueue empty() method returns True if the priority queue is empty. This module provides an implementation of the heap queue algorithm, also known as the priority queue algorithm. If I had time or any real knowledge of how to use Python, I would have liked to have tried it, but again I didn't really have time for more than a bare-minimum-functional solution.Īnd I'm only posting this here for propriety. or in decent way, use get and taskdone pair to safely clear the tasks. with q.mutex: q.queue.clear () q.alltasksdone.notifyall () q.unfinishedtasks 0. And alltasksdone needs to be notified also. I would like to acknowledge user2357112-supports-Monica's suggestion to go with a custom heap implementation. You just can not clear the queue, because every put also add the unfinishedtasks member. And then to get the item out: current = pq.get().item. put() with a tuple, put the entire PrioritizedItem class in instead pq.put(PrioritizedItem(0, start)) or pq.put(PrioritizedItem(priority, data)). from dataclasses import dataclass, fieldĪnd then instead of using. If there's anyone that's looking at this that just really doesn't understand how Python works (like me!), stick this at the top. But at this point there might be no items left. The problem is in the pop method: it calls clearheap after popping the item (as well as before). I plan to use it in graph search algorithms so the values associated with each key are update-able. The solution was basically just implement the suggestion here. Here is my attempt to implement a minimum priority queue class in Python using the heapq module. Ok, just in case someone ends up here, I ended up taking superb rain's comment into consideration since I was looking for a simpler solution, and I didn't really have time to overhaul my solution to make it more efficient or better. I did find this solution, but it doesn't use a PriorityQueue, so I'm not sure if I can do something similar, or if this isn't possible altogether (in which case I'll have to modify my algorithm to be whatever this is, which is not preferable.). The exact order in which objects of the same priority are sorted is completely unimportant to me. TypeError: '<' not supported between instances of 'InfNode' and 'InfNode'īasically, I am looking for a way to bypass the PriorityQueue trying to compare these two objects. This is the relevant part of the error: File "pathfinding.py", line 192, in astarįile "/usr/lib/python3.7/queue.py", line 149, in putįile "/usr/lib/python3.7/queue.py", line 233, in _put pq.put(1, object)) when it's already holding a tuple with the same priority. I'm using it to hold objects that are non-comparable (an object class provided by a professor that I cannot modify), and Python throws an error when it tries to add an priority-object tuple (ex. I am using Python's Queue.PriorityQueue (in an implementation of the A* algorithm, though I'm not sure if this is relevant).
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