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Q:

queues in python

# Python program to  
# demonstrate queue implementation 
# using list 
  
# Initializing a queue 
queue = [] 
  
# Adding elements to the queue 
queue.append('a') 
queue.append('b') 
queue.append('c') 
  
print("Initial queue") 
print(queue) 
  
# Removing elements from the queue 
print("\nElements dequeued from queue") 
print(queue.pop(0)) 
print(queue.pop(0)) 
print(queue.pop(0)) 
  
print("\nQueue after removing elements") 
print(queue) 
  
# Uncommenting print(queue.pop(0)) 
# will raise and IndexError 
# as the queue is now empty 
3
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()
6
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()

4
"""put and get items from queue"""
>>> from Queue import Queue
>>> q = Queue()
>>> q.put(1)
>>> q.put(2)
>>> q.put(3)
>>> print list(q.queue)
[1, 2, 3]

>>> q.get()
1
>>> print list(q.queue)
[2, 3]
0

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