Hi Todd

You wrote:
Do we have an agreement on the API as Guido requested?  From my understanding, and please correct me if I am wrong, you are still talking about implementing this using a new class.  However, most people who support the use of labelled indexing.and expressed an opinion support a keyword argument-based approach.  

 Thank you for your prompt and close interest. For clarity, I don't think we have agreement on the API. (While I was writing this message, Guido posted a similar view.)

I see my kwargs package as a way of exploring the design of the API. To help, let me give you a guided tour of some of the files in the package.

You'll find the following code

    from .jfine import key_to_jfine

    Point = namedtuple('Point', ('x', 'y'))
    class PointMap(dict):
        def __setitem__(self, val, x, y):
            pnt = Point(x, y)
            dict.__setitem__(self, pnt, val)

in https://github.com/jfine2358/python-kwkey/blob/master/kwkey/example_jfine.py

The decorator key_to_jfine comes from the kwkey.jfine submodule. It implements the API that I favour. This is my first contribution to the exploration of the API.

The kwkey.sdaprano implements, I believe, the API that Steven D'Aprano favours. I believe that from this he (or anyone else such as you) can similarly implement example_sdaprano, example_todd and so forth.

Also implemented are kwkeys.test_jfine and kwkey.test_sdaprano submodules. Although a bit cryptic, they do show what is going on.

For example, jfine gives
    # Arguments passed to setitem.
    >>> d[o(1, 2, a=3, b=4)] = 'val'
    (('val', 1, 2), {'a': 3, 'b': 4})
while sdaprano gives
    # Arguments passed to setitem.
    >>> d[o(1, 2, a=3, b=4)] = 'val'
    ((1, 2), 'val', {'a': 3, 'b': 4})

In case it's needed, the current tree, referred to above, is

Many thanks to Ricky Teachey, who discovered the resources above, and who kindly wrote

I'm really interested in this and it's very helpful that you included two versions of the proposed API for people to try out: the jfine version (with the kw object) and the stevedaprano version (with kwd arguments passed directly to the dunder methods).

This is I think nicely explained. (Nitpick. I called it sdaprano.py, to align with jfine.py.)

 I think it would be really helpful if Steven could confirm or correct my implementation of his proposed API. I think it would also be really helpful to have an example that uses his API. It needn't be the same example as the one I've written.

I hope this helps (and does no harm).