[fulafel]

They're pretty simple in many dynamic languages, eg you can just do "import os; dir(os)" in Python.

[kevingadd]

yeah, but that doesn't mean they're fast or don't make a mess of the gc heap

[fulafel]

I hadn't heard people use messy to refer to garbage cration before!

To continue with Python, yes, you might get a new container (dict) allocated like in the above case to hold the already existing interned attribute name strings. It's still quite light since the object representing the information already exist and are used under the hood in the dynamic typing machinery.