text: import os
  #
  
  
  class bag(object):
      '''
      @brief  背包
      相关的函数简单明了不做注释
      '''
      def __init__(self):
          super(bag, self).__init__()
          self._data = []
  
  
      def add(self, ele):
          self._data.append(ele)
  
      def empty(self):
          return len(self._data) == 0
  
      def size(self):
          return len(self._data)
  
      def __iter__(self):
          return self._data.__iter__()
  
      def __getitem__(self, index):
          return self._data[index]
  
  
  def main():
      pass
  if __name__ == '__main__':
      main()