Talk is cheap

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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# @Date    : 2018-08-09 10:42:22
# @Author  : Simon (simon.xie@codewalker.meg)
# @Link    : http://www.codewalker.me
# @Version : 1.0.0


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


class LinkedList(object):
    def __init__(self, head=None):
        self.head = head

    def append(self, new_element):
        current = self.head
        if self.head:
            while current.next:
                current = current.next
            current.next = new_element
        else:
            self.head = new_element

    def insert_first(self, new_element):
        "Insert new element as the head of the LinkedList"
        current = self.head
        self.head = new_element
        new_element.next = current

    def delete_first(self):
        "Delete the first (head) element in the LinkedList as return it"
        current = self.head.next
        self.head = current


class Stack(object):
    def __init__(self, top=None):
        self.ll = LinkedList(top)

    def push(self, new_element):
        "Push (add) a new element onto the top of the stack"
        self.ll.insert_first(new_element)

    def pop(self):
        "Pop (remove) the first element off the top of the stack and return it"
        if self.ll.head == None:
            return None
        current = self.ll.head
        self.ll.delete_first()
        return current


def main():
    # Test cases
    # Set up some Elements
    e1 = Element(1)
    e2 = Element(2)
    e3 = Element(3)
    e4 = Element(4)

    # Start setting up a Stack
    stack = Stack(e1)

    # Test stack functionality
    stack.push(e2)
    stack.push(e3)
    print(stack.pop().value)
    print(stack.pop().value)
    print(stack.pop().value)
    print(stack.pop())
    stack.push(e4)
    print(stack.pop().value)


if __name__ == "__main__":
    main()