person = {
          'name': Jane,
          'yearofbirth': 1995,
          'yearnow': 2019,
          'age': person['yearnow'] + person['yearofbirth']
        }

class MyDict(dict):
   def __getitem__(self, item):
       return dict.__getitem__(self, item) % self

dictionary = MyDict({

    'user' : 'gnucom',
    'home' : '/home/%(user)s',
    'bin' : '%(home)s/bin'
})


print dictionary["home"]
print dictionary["bin"]