# -*- coding: utf-8 -*- 
# @Time : 2018/3/26 16:14 
# @Author : Lv Zhangrun 
# @Site :  
# @File : Stack.py 
# @Software: PyCharm
class Stack:
    """模拟栈"""

    def __init__(self):
        self.items = []

    def isEmpty(self):
        return len(self.items) == 0

    def push(self, item):
        self.items.append(item)

    def pop(self):
        return self.items.pop()

    def peek(self):
        if not self.isEmpty():
            return self.items[len(self.items) - 1]

    def size(self):
        return len(self.items)