Implement Queue Using Two Stacks in Python

class QueueUsingStacks:
    def __init__(self):
        self.stack_in = []
        self.stack_out = []

    def enqueue(self, value):
        self.stack_in.append(value)

    def dequeue(self):
        if not self.stack_out:
            while self.stack_in:
                self.stack_out.append(self.stack_in.pop())
        return self.stack_out.pop()

    def peek(self):
        if not self.stack_out:
            while self.stack_in:
                self.stack_out.append(self.stack_in.pop())
        return self.stack_out[-1]

    def is_empty(self):
        return not self.stack_in and not self.stack_out

    def display(self):
        combined = self.stack_out[::-1] + self.stack_in
        print("Queue contents (front to back):", combined)


if __name__ == "__main__":
    q = QueueUsingStacks()
    q.enqueue(1)
    q.enqueue(2)
    q.enqueue(3)
    q.display()
    print("Dequeued:", q.dequeue())
    q.display()
    q.enqueue(4)
    print("Peek:", q.peek())
    q.display()
    print("Is empty:", q.is_empty())