> Almost, he is also converting ordinary dicts that get added as items to his own Dict class

You are right I dind't notice that before. But looking at the code it seems that the only permitted values are dict and str?!

> But yes, the idea of storing everything twice (once as an item and once as an attribute) I don't get that, you don't store things twice and nothing breaks, at least with the example code I wrote above. Try:

  >>> a=D()
  >>> a.lol = 2
  >>> a['get'] = 'foo'
  >>> a
  {'get': 'foo', 'lol': 1}
  >>> vars(a)
  {}