Q.How can you avoid printing of None, when trying to print an empty queue?

Shape: Plain theory question — asks for a technique to suppress None when printing an empty queue.

When you implement a queue using a Python list and write a method to display its contents, a common pattern is:

def display(self):
    if not self.queue:
        print("Queue is empty")
    else:
        print(self.queue)

If you instead write display to return a value and then print the result, you run into the problem:

def display(self):
    if not self.queue:
        return None  # or implicitly return None
    else:
        return self.queue

print(q.display())  # prints "None" when queue is empty

The issue is that print(None) outputs the string None, which is not user-friendly.

Three clean solutions:

1. Check before printing (caller's responsibility):

   result = q.display()
   if result is not None:
       print(result)
   

2. Print inside the method, don't return (recommended for display methods):

   def display(self):
       if not self.queue:
           print("Queue is empty")
       else:
           print(self.queue)
   

   Now calling q.display() directly prints the appropriate message; there is nothing to capture or print again.

3. Return a meaningful string instead of None:

   def display(self):
       if not self.queue: …
   

When you implement a queue using a Python list and write a dequeue() method, the natural instinct is to check if the queue is empty and simply return without a value. But here's the problem: a bare return statement in Python implicitly returns None. So when you write print(q.dequeue()) on an empty queue, you see None printed to the console — not very user-friendly.

The issue arises because Python functions that don't explicitly return a value evaluate to None. If your dequeue method looks like this:

def dequeue(self):
    if len(self.queue) == 0:
        return  # implicit None
    return self.queue.pop(0)

then calling print(q.dequeue()) on an empty queue prints None.

The solution: return a descriptive string

Instead of returning nothing (which becomes None), return an explicit message string that describes the underflow condition:

def dequeue(self):
    if len(self.queue) == 0:
        return "Queue is empty"  # or "Underflow" or any message
    return self.queue.pop(0)

Now when you print the result of dequeuing from an empty queue, you get a clear, readable message instead of None.

Complete example

class Queue:
    def __init__(self):
        self.queue = []
    
    def enqueue(self, item):
        self.queue.append(item)
    
    def dequeue(self):
        if len(self.queue) == 0:
            return "Queue is empty"
        return self.queue.pop(0)
    
    def display(self):
        print(self.queue)

# Usage
q = Queue()
print(q.dequeue())  # prints: Queue is empty
q.enqueue(10)
q.enqueue(20)
print(q.dequeue())  # prints: 10
print(q.dequeue())  # prints: 20
print(q.dequeue())  # prints: Queue is empty

Output:

Queue is empty
10
20 …