Implementation of Stack using Linked List

stack_using_linked_list.py

class Node(object):
    """
    Fundamental building block of a linked list
    A node consists of a value and the next node location pointer
    """

    def __init__(self, value):
        self.val = value
        self.next = None


class MyStack(object):
    """
    Stack implementation using LinkedList 
    Stack is a LIFO queue
    """

    def __init__(self):
        """
        Initialize stack
        """
        self.head = None

    def pushItem(self, val):
        """
        Push new value to stack
        (Push the new value to the front of linked list - O(1))
        """
        newItem = Node(val)
        newItem.next = self.head
        self.head = newItem

    def popItem(self):
        """
        Pop the top value of the stack 
        (Pop the new value from the front of linked list - O(1))
        """
        try:
            self.head = self.head.next
        except AttributeError as error:
            self.head = None

    def peekItem(self):
        """
        Peek the top value of stack
        (Peek the top value the front of linked list - O(1))
        """
        try:
            return self.head.val
        except AttributeError as error:
            return None

    def isEmpty(self):
        """
        Check is stack is empty
        (Check if head of linked list is none - O(1))
        """
        return self.head is None

# if __name__ == "__main__":

#     myStack = MyStack()

#     print("Top value of stack: ", myStack.peekItem())

#     myStack.pushItem(8)
#     myStack.pushItem(7)

#     print("Top value of stack: ", myStack.peekItem())

#     myStack.popItem()

#     print("Top value of stack: ", myStack.peekItem())

#     myStack.popItem()
#     myStack.popItem()
#     myStack.popItem()

#     print("Is empty: ", myStack.isEmpty())

#     print("Top value of stack: ", myStack.peekItem())