T1 = threading. Here's an example: from queue import PriorityQueue While holding onto the queue object would be even less threadsafe, because that queue object is "live" (see this answer), you can still run into issues when accessing the objects on the queue if you expect the object ordering to be static. The above answers show how to access the elements of a PriorityQueue, however there is some danger when accessing objects from the inner queue in a multithreaded manner (as mentioned at the end of HYRY's answer). # python3 test_priority_queue.pyįile "test_priority_queue.TL DR - If you are are using the top item multiple times in a multithreaded environment, you should assign the item to a variable. Note that it's still one of the first elements placed into the priority queue that is in the wrong order. get():īad, not completely sorted output (~30% of the time): # python3 test_priority_queue.pyįile "test_priority_queue.py", line 129, in Īdditional, bad, example. Priorities of the items in the PriorityQueue as they were popped off of the queue via. Good, expected output (~70% of the time): # python3 test_priority_queue.py You get the result since in sorting a string, h < hello < oh is True. Print("All checks have passed successfully!") Priority queue does a heapq sort (as pointed out in the comments) on the tuples (where the first value counts first, and when encountering equal in the first 'column', will it compare the second). # priorities read off of the priority queue are sorted low to highĪssert len(priorities) = len(data) = NUM_EXAMPLES # Ensure that the queues have been fully read from and the Confused on Deitels wording in regards to highest-priority element in a priority queue. How to poll the RabbitMQ to get messages in order of priority continuously 0. Print(f"Placing into the PriorityQueue: ") Priority queue with higher priority first in Python. # priority_number: float = round(np.random.normal(), 3)Ī = The final item placed in the priority queue will have a priority of 999.0 Write data to the priority queue with random priorities Prioritized item for priority queue as recommended at:ĭef _init_(self, priority: float, data: int = 0):ĭef writer_function(priority_queue_under_test: PriorityQueue, PQManager.register("PriorityQueue", PriorityQueue) PriorityQueue and a reader process to read data from the PriorityQueue.Įnsure the data read out of the PriorityQueue is sorted by priorityįrom _future_ import annotations # For type hinting the values in PriorityQueueįrom multiprocessing.managers import SyncManager Test the PriorityQueue class by making a writer process to write data into the I have verified the issue in both Python 3.7.13 and 3.10.7. Perhaps the answered PriorityQueue isn't actually thread/process safe? If so, how can I make it thread/process safe? If you run it a few times, eventually you should see an assertion error. I wrote a unit test of sorts for the answer mentioned above. I tried having the priority queue take in tuples of (priority, data), I also tried using a same result. I followed this answer to create the multiprocessing priority queue. I think that should be a hint to the problem but I don't know why that is. Most often when they are returned incorrectly, the first item returned from the priority queue is incorrect and it corresponds to the first (or one of the first) item placed in the priority queue. get() returns from my priority queue are ~70% of the time 100% correctly sorted, but ~30% of the time they will only be ~70% sorted correctly, with most of the elements correct but a few elements shuffled incorrectly.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |