On Fri, Sep 25, 2020 at 11:50 PM Steven D'Aprano <steve@pearwood.info> wrote:
1. We have to pass a sentinel to the setitem dunder if there is no positional index passed.
I still don't follow this logic -- why can't nothing be passed? The dunders either require an index or they don't, would that be just like function calling? So (adapting the example in the PEP: obj[spam=1, eggs=2] # calls type(obj).__getitem__(obj, spam=1, eggs=2) This sure seems like the obvious way to handle it. If the class requires a positional argument then it will fail with a TypeError. This sure seems like the most straightforward way to handle it. I'm sure I'm missing something, but reading the PEP, and my own experiments haven't clarified it for me. NOTE: one inconsistency would be that: obj[] would be a SyntaxError, and obj[this=x] would be a TypeError, if a positional index were expected. but that's less weird to me than the other incionsisentcies we are introducing for backward compatibility. -CHB -- Christopher Barker, PhD Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython