implement_stack_linkedList.py

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

class Stack:
    def __init__(self):
        self.head = None
        self.num_elements = 0
    def to_list(self):
        py_list = []
        node = self.head
        while node:
            py_list.append(node.value)
            node = node.next
        return py_list
    def push(self, value):
        if self.head is None:
            self.head = Node(value)
        else:
            new_node = Node(value)
            new_node.next = self.head
            self.head = new_node
        self.num_elements += 1
    def size(self):
        return self.num_elements
    def is_empty(self):
        return self.num_elements == 0   
    def pop(self):
        if self.head is None:
            return None
        value = self.head.value
        self.head = self.head.next
        self.num_elements -=1
        return value


stack = Stack()
stack.push(10)
stack.push(20)
stack.push(30)
stack.push(40)
stack.push(50)

# Test size
print ("Pass" if (stack.size() == 5) else "Fail")

# Test pop
print ("Pass" if (stack.pop() == 50) else "Fail")

# Test push
stack.push(60)
print ("Pass" if (stack.pop() == 60) else "Fail")
print ("Pass" if (stack.pop() == 40) else "Fail")
print ("Pass" if (stack.pop() == 30) else "Fail")
stack.push(50)
print ("Pass" if (stack.size() == 3) else "Fail")