#coding:utf-8#author:Elvis class Stack(object):   def __init__(self, size=8):    self.stack = []    self.size = size    self.top = -1   def is_empty(self):    if self.top == -1:      return True    else:      return False   def is_full(self):    if self.top +1 == self.size:      return True    else:      return False   def push(self, data):    if self.is_full():      raise Exception('stackOverFlow')    else:      self.top += 1      self.stack.append(data)   def stack_pop(self):    if self.is_empty():      raise Exception('stackIsEmpty')    else:      self.top -= 1      return self.stack.pop()    def stack_top(self):    if self.is_empty():      raise Exception('stackIsEmpty')    else:      return self.stack[self.top]   def show(self):    print self.stack stack = Stack()stack.push(1)stack.push(2)stack.push('a')stack.push('b')stack.push(5)stack.push(6)stack.stack_pop()stack.stack_pop()stack.stack_top()stack.is_empty()stack.is_full()stack.show()