The script continues to present the menu options to the user until they choose to exit.Īgain, as the name says, in this type of queue, the element that goes in first comes out last. Overall, this script creates a menu-driven interface where the user can add elements to a queue, remove elements from the queue, display the elements in the queue, or exit the program. If the user enters an invalid choice (other than `’1’`, `’2’`, `’3’`, or `’4’`), we display a message indicating that the choice is invalid, and the loop continues to prompt the user for another choice. If the user enters `’4’`, we display a message indicating that the program is exiting, and then we break out of the loop, ending the program. If the queue is empty, we display a message indicating that the queue is empty. If the queue is not empty, we print all the elements in the queue using a `for` loop. If the user enters `’3’`, we again check if the queue is not empty (`len(queue) > 0`). If the queue is not empty, we use the `popleft()` method to remove the element at the front of the queue, and we print the removed element. If the user enters `’2’`, we first check if the queue is not empty (`len(queue) > 0`). Print(“Removed element:”, removed_element) We display a message indicating that the element has been added to the queue. The element is then appended to the end of the queue using the `append()` method. If the user enters `’1’`, we prompt them to enter an element to add to the queue using the `input()` function. Perform the corresponding action based on the user’s choice:Įlement = input(“Enter an element to add: “).The user’s input is stored in the `choice` variable as a string. We use the `input()` function to prompt the user to enter their choice. We print the menu options to the console, presenting the available actions to the user.Ĭhoice = input(“Enter your choice (1-4): “) We use an infinite `while` loop, which means the loop will keep running until we explicitly break out of it. This creates an empty queue object that we will use to store the elements. We create an empty queue using the `deque()` constructor from the `deque` class. The `deque` class provides an implementation of a double-ended queue, which we will use to create a queue data structure. Here, we import the `deque` class from the `collections` module. T1 = threading.Let’s go through the code step by step to understand how the menu-driven script works: Which will print something like the below: FirstAccess: (0, 0)įor this reason, if you want to use an object from the top of a PriorityQueue, you should assign that object to a name: from queue import PriorityQueue T1 = threading.Thread(target=queue_manip) 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). TL DR - If you are are using the top item multiple times in a multithreaded environment, you should assign the item to a variable.
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