python实现栈

# 先进后出 砌墙的砖头
  class Stack():
    def __init__(self, size):
        self.size = size
        self.stack = []
        self.top = 0 # 栈顶指针

    # 入栈之前检查栈是否已满
    def push(self, x):
        if self.isfull():
            raise Exception("stack is full")
        else:
            self.stack.insert(self.top, x)
            self.top = self.top + 1

    # 出栈之前检查栈是否为空
    def pop(self):
        if self.isempty():
            raise Exception("stack is empty")
        else:
            self.top = self.top - 1
            return self.stack.pop()

    def isfull(self):
        return self.top == self.size

    def isempty(self):
        return self.top == 0

    def showStack(self):
        return self.stack