front,rear=0,0 #front for dequeue, rear for enqueue global variables

size=4 # size of the list

a = [0]*size # initializing the list with all zeros

def enqueue(data):

global rear #using global rear

if(rear<size): #checking the size of list

a[rear]=data

rear+=1 #increment rear so that it holds the position for the next element to be inserted

else:

print("queue is full")

enqueue(1) #inserting 1

enqueue(2) #inserting 2

enqueue(3) #inserting 3

enqueue(4) #inserting 4

print(a)

enqueue(5) # insering 5 will output queue full message

# refering to the queue we have created in the above code snippet

def dequeue():

global front

if(front>=rear): #check if queue is empty

print("Queue is empty")

else:

print("Dequeue element value :",a[front])

front+=1 #increment front so that it points to the next element in queue

dequeue() # takes out 1

dequeue() # takes out 2

dequeue() # takes out 3

dequeue() # takes out 4

dequeue() # outputs queue is empty as all the elements are taken out

# return true if queue is empty else returns false

def isEmpty(queue):

global front,rear

if(front==rear):

return True

else:

return False

print(isEmpty(a)) # as the queue is empty it will return true

# outputs the topmost element of the queue

def peek():

global rear

if(rear==front):

print("queue is empty")

else:

print("The topmost element is :",a[rear])

peek()