x = dd()
    print(x.tyypo.a.b)

The problem is that an object can't know whether you're getting a node that you're later going to assign a leaf to... or whether you're getting the node because you want to get the node.

   x = dd()
   x.a.b.c = "Foo"

   x = dd()
   y = x.a.b
   y.c = "Foo"

Now, it's python, so you can do unholy things to make pretty much anything work. But I think it would be ugly.

   if a.b.c:
       print("c:", a.b.c)