queue implementation pythonm code example

Example 1: queue python

from queue import Queue

q = Queue()

q.size() # returns the current lenght of queue
q.empty() # returns True if empty, False otherwise
q.put(item) 
q.get()

Example 2: queues in python

class Queue:
    def __init__(self, capacity):
        self.front = self.size = 0
        self.rear = capacity - 1
        self.Q = [None] * capacity
        self.capacity = capacity

    def isFull(self):
        return self.size == self.capacity

    def isEmpty(self):
        return self.size == 0

    def EnQueue(self, item):
        if self.isFull():
            print("Full")
            return

        self.rear = (self.rear + 1) % (self.capacity)
        self.Q[self.rear] = item
        self.size = self.size + 1
        print("%s enqueue to queue" %str(item))

    def DeQueue(self):
        if self.isEmpty():
            return "Empty"

        print("%s dequeued from queue" %str(self.Q[self.front]))
        self.front = (self.front + 1) % (self.capacity)
        self.size = self.size - 1

    def que_front(self):
        if self.isEmpty():
            print("The Queue is empty")


        print("Front item is ", self.Q[self.front])

    def que_rear(self):
        if self.isEmpty():
            print("Queue is Empty")

        print("The rear item is ", self.Q[self.rear])


queue = Queue(30)
queue.EnQueue(10)
queue.EnQueue(20)
queue.EnQueue(30)
queue.EnQueue(40)
queue.EnQueue(50)
queue.que_front()
print()
queue.DeQueue()
queue.que_front()
queue.que_rear()
print()
queue.DeQueue()
queue.que_front()
queue.que_rear()

Example 3: python queue.priority queue

from queue import PriorityQueue

class PqElement(object):
    def __init__(self, value: int):
        self.val = value

    #Custom Compare Function (less than or equsal)
    def __lt__(self, other):
        """self < obj."""
        return self.val > other.val

    #Print each element function
    def __repr__(self):
        return f'PQE:{self.val}'

#Usage-
pq = PriorityQueue()
pq.put(PqElement(v))       #Add Item      - O(Log(n))
topValue = pq.get()        #Pop top item  - O(1)
topValue = pq.queue[0].val #Get top value - O(1)

Example 4: py list enqueue

a = [1,2,3,4]

# enqueue
a = [0] + a
>>> [0,1,2,3,4]