Data-Structures-and-Algorithms-in-Python/Stack.py at master · abhi227070/Data-Structures-and-Algorithms-in-Python · GitHub

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class Node:

    def __init__(self, value):

        self.data = value
        self.next = None

class Stack:

    def __init__(self):

        self.top = None
        self.n = 0

    def __len__(self):
        return self.n

    def push(self, value):

        new_node = Node(value)

        new_node.next = self.top
        self.top = new_node
        self.n += 1

    def isempty(self):
        return self.top == None

    def __str__(self):
        curr = self.top

        while curr != None:

            print(curr.data)
            curr = curr.next

        return ''

    def peak(self):

        if self.top == None:
            print("Stack is empty.")
            return

        else:
            return self.top.data

    def pop(self):

        if self.top == None:
            print("Stack is empty")
            return

        else:

            self.top = self.top.next
            self.n -= 1


if __name__ == "__main__":

    stack = Stack()

    stack.push(1)
    stack.push(2)
    stack.push(3)
    stack.push(4)

    stack.pop()
    print(stack.isempty())
    print(stack.peak())

    print(stack)