Stack in Python

#A stack is a linear data structure that stores items in a Last-In/First-Out (LIFO) or First-In/Last-Out (FILO) manner

class Node:
    def __init__(self, data):
        self.data = data
        self.ref = None


class Stack:
    def __init__(self):
        self.__head = None
        self.__size = 0

    def push(self, data):
        # adds an element at the beginning
        self.__size += 1
        new_node = Node(data)
        new_node.ref = self.__head
        self.__head = new_node

    def pop(self):
        # deletes element from beginning
        if self.isEmpty():
            print("Stack is empty.")
            return
        self.__size -= 1
        print(self.__head.data)
        self.__head = self.__head.ref

    def top(self):
        # prints the topmost element, i.e, head in the case of LL
        if self.isEmpty():
            print("Stack is empty.")
            return
        print(self.__head.data)

    def isEmpty(self):
        return(self.__size == 0)

    def display(self):
        # displays the stack from top to bottom
        n = self.__head
        if n is None:
            print("Empty!")
            return
        while n is not None:
            print(n.data)
            n = n.ref


if __name__ == "__main__":
    s2 = Stack()
    print("Enter values to push in the stack: ")
    value = [ele for ele in input().split()]
    for i in range(len(value)):
        s2.push(value[i])
    print("The stack is:")
    s2.display()
    print('\nThe first element which is removed is: ')
    s2.pop()
    print('\nThe topmost element of the stack is:')
    s2.top()
    print("\nThe stack is:")
    s2.display()


"""Time-Complexity of the program:
push(): O(1)
pop(): O(1)
top(): O(1)
display(): O(N)
"""

"""Test-Cases:
>>>
Enter values to push in the stack:
10 15 23 42
The stack is:
42
23
15
10
The first element which is removed is:
42
The topmost element of the stack is:
23
The stack is:
23
15
10
>>>
Enter values to push in the stack:
Jack
The stack is:
Jack
The first element which is removed is:
Jack
The topmost element of the stack is:
Stack is empty.
The stack is:
Empty!
>>>
Enter values to push in the stack:
Jack 1 QWERTY 22 key 87
The stack is:
87
key
22
QWERTY
1
Jack
The first element which is removed is:
87
The topmost element of the stack is:
key
The stack is:
key
22
QWERTY
1
Jack
"""