On Mon, Aug 03, 2020 at 05:51:58PM -0400, Ricky Teachey wrote: > However I'll also point out that another idea from Jonathan Fine has the > potential to fix both this problem and the key object signature problem, > which is what he called a "SIGNATURE CHANGING ADAPTER". > > > > Here's how it goes. First we write > > class D: > > @wibble > > def __setitem__(self, val, u, v, x, y): > > pass # Or do something. > > > > Next, we define wibble. It will be a SIGNATURE CHANGING ADAPTER. Those > > who know how to make decorators will, I hope, have little difficulty in > > defining wibble to do what is required. For this exercise, assume that > > k.argv = (1, 2), and k.kwargs = dict(x=3, y=4).
Good news! Thanks to Guido's time machine, Python already supports this signature changing adapter for functions and methods. All you have to do is *leave the decorator out*. In fact you don't even have to define it at all. The Python interpreter already knows how to match up keyword arguments like `u=35` and their associated parameters `u`. So we don't have to duplicate the argument parsing logic of the interpret in a decorator. We just have to let the interpreter do its thing like it already does. This is (almost) as flexible as you want: Want your keyword arguments to be optional? Define them with a default. Want them to be mandatory? No default. Want to accept arbitrary keyword arguments? Include a `**kwargs` parameter. Want all of your keywords bundled together? Use only a `**kwargs` parameter. The only limitation is that subscripting syntax bundles all positional arguments into a single parameter, for reasons lost deep in the mists of time. But that doesn't affect keyword parameters. -- Steven _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/6PDHEE5PBH54SPWHJF6JKYS2WJDSQICG/ Code of Conduct: http://python.org/psf/codeofconduct/
