new_contents: #!/usr/bin/env python
  # coding=utf-8
  
  
  class Skills:
  
      def __init__(self, **kwargs):
          self.skills = set(kwargs.values())
  
      def __repr__(self):
          return 'Skills: {}'.format(','.join(i for i in self.skills))
  
      def __len__(self):
          return len(self.skills)
  
      def learn(self, new_skill):
          print '新技能 {} get'.format(new_skill)
          return self.skills.add(new_skill)
  
      def forget(self, old_skill):
          return self.skills.discard(old_skill)
  
  if __name__ == '__main__':
      I = Skills(a='swim', b='basketball')
      print I
      I.learn(new_skill='python')
      print I
      print len(I)
  
subject: create a class