import UserDict

class C(UserDict.UserDict):
  def __init__(self, initial):
    UserDict.UserDict.__init__(self,initial)
    self._positions = initial.keys()
    self._positions.sort()
    
  def __getitem__(self, index):
    if type(index) == type(0):
      index = self._positions[index]
    return UserDict.UserDict.__getitem__(self, index)

c = C({'key1':'value1','key2':'value2'})

for i in c:
  print i