To get back on topic a little bit, lets get back to the syntax of all this: I think we all agree that recycling the function call syntax is less than ideal, since while it works in special contexts like a function signature, its symmetric counterpart inside a function call already has the meaning of a function call.
In general, we face the problem of specifying metadata about a variable, or a limited form of type constraint. What we want is similar to function annotations in python 3; in line with that, we could have more general variable annotations. With an important conceptual distinction; function annotations are meaningless to python, but the annotations I have in mind should modify semantics directly. However, its still conceptually close enough that we might want to use the colon syntax here too. To distinguish it from function annotations, we could use a double colon (double colon is an annotation with non-void semantics; quite a simple rule); or to maintain an historic link with the existing packing/unpacking syntax, we could look at an augmented form of the asteriks notation. For instance: def func(list*args, dict*kwargs) <- list-of-args, dict-of-kwargs def func(args::list, kwargs::dict) <- I like the readability of this one even better; args-list and kwargs-dict And: head, deque*tail = somedeque head, tail::deque = somedeque Or some variants thereof -- http://mail.python.org/mailman/listinfo/python-list
