deque.py

# Copyright (C) Deepali Srivastava - All Rights Reserved
# This code is part of DSA course available on CourseGalaxy.com  

class EmptyQueueError(Exception):
    pass

class Deque:
    def __init__(self):
        self.items = []

    def is_empty(self):
        return self.items == []

    def size(self):
        return len(self.items)

    def insert_front(self, item):
        self.items.insert(0,item)
    
    def insert_rear(self, item):
        self.items.append(item)

    def delete_front(self):
        if self.is_empty():
            raise EmptyQueueError("Queue is Empty")
        return self.items.pop(0)
        
    def delete_rear(self):
        if self.is_empty():
            raise EmptyQueueError("Queue is Empty")
        return self.items.pop()

    def first(self):
        if self.is_empty():
            raise EmptyQueueError("Queue is Empty")
        return self.items[0]

    def last(self):
        if self.is_empty():
            raise EmptyQueueError("Queue is Empty")
        return self.items[-1]
    
    def display(self):
        print(self.items)

####################################################################
if __name__ == "__main__":
    qu = Deque()

    while True:
        print("1.Insert at the front end")
        print("2.Insert at the rear end")
        print("3.Delete from front end")
        print("4.Delete from rear end")
        print("5.Display first element")
        print("6.Display last element")
        print("7.Display")
        print("8.Size")
        print("9.Quit")
             
        choice = int(input("Enter your choice : "))

        if choice == 1:
            x=int(input("Enter the element : "))
            qu.insert_front(x)
        elif choice== 2:
            x=int(input("Enter the element : "))
            qu.insert_rear(x)
        elif choice == 3:
            x = qu.delete_front()
            print("Element deleted from front end is  ", x)
        elif choice == 4:
            x = qu.delete_rear()
            print("Element deleted from rear end is  ", x)
        elif choice == 5:
            print("First element is  ", qu.first())
        elif choice == 6:
            print("Last element is  ", qu.last())
        elif choice == 7:
            qu.display()
        elif choice == 8:
            print("Size of queue " , qu.size())
        elif choice == 9:
            break
        else:
            print("Wrong choice")
        print()