Implementation of Queue in Python List

#Queue Implementation in Python List

#Function to check the queue is empty or not.

def isEmpty(Qu):

    if Qu==[]:

        return True

    else:

        return False

#Function to insert the value in the queue.

def EnQueue(Qu,val):

    Qu.append(val)

    if len(Qu)==1:

        front=rear=0

    else:

        rear=len(Qu)-1

#Function to remove the value from the front of the queue

def DeQueue(Qu):

    if isEmpty(Qu):

        return "Underflow"

    else:

        val=Qu.pop(0)

    if len(Qu)==0:

        front=rear=None

    return val

#Function to inspect the position of the front in queue

def Peek(Qu):

    if isEmpty(Qu):

        return "Underflow"

    else:

        front=0

    return Qu[front]

#Function to display the queue values

def Display(Qu):

    if isEmpty(Qu):

        print("Queue is Empty, Nothing to display")

    elif len(Qu)==1:

        print(Qu[0],"<==Front,rear")

    else:

        front=0

        rear=len(Qu)-1

        print(Qu[0],"<==Front")

        for i in range(1,rear):

            print(Qu[i])

        print(Qu[rear],"<==Rear")

#__main__

queue=[]        #Initially queue is empty list

front=None

while True:

    print("QUEUE OPERATION MENU")

    print("1. Enqueue")

    print("2. Dequeue")

    print("3. Peek")

    print("4. Display")

    print("5. Exit")

    ch=int(input("Enter your choice: "))

    if ch==1:

        n=int(input("Enter value: "))

        EnQueue(queue,n)

    elif ch==2:

        n=DeQueue(queue)

        if n=="Underflow":

            print("Underflow!!! queue is empty")

        else:

            print("Deleted value is:",n)

    elif ch==3:

        n=Peek(queue)

        if n=="Underflow":

            print("Underflow!!! queue is empty")

        else:

            print("Front value is:",n)

    elif ch==4:

        Display(queue)

    elif ch==5:

        break;

    else:

        print("Invalid choice")

Output:

QUEUE OPERATION MENU

1. Enqueue

2. Dequeue

3. Peek

4. Display

5. Exit

Enter your choice: