I actually think the spelling is the main stumbling block. The intrinsic value of the behavior is clear, it's finding an acceptable spelling that hold back the proposal.
I propose that the next phase of the process should be to pick the best operator for each sub-proposal. Then we can decide which of the sub-proposals we actually want in the language, based on a combination of how important the functionality is and how acceptable we find the spelling. --Guido On Thu, Oct 13, 2016 at 8:20 PM, Mark E. Haase <meha...@gmail.com> wrote: > (Replying to multiple posts in this thread) > > Guido van Rossum: >> >> Another problem is PEP 505 -- it >> is full of discussion but its specification is unreadable due to the >> author's idea to defer the actual choice of operators and use a >> strange sequence of unicode characters instead. > > > Hi, I wrote PEP-505. I'm sorry that it's unreadable. The choice of emoji as > operators was supposed to be a blatant joke. I'd be happy to submit a new > version that is ASCII. Or make any other changes that would facilitate > making a decision on the PEP. > > As I recall, the thread concluded with Guido writing, "I'll have to think > about this," or something to that effect. I had hoped that the next step > could be a survey where we could gauge opinions on the various possible > spellings. I believe this was how PEP-308 was handled, and that was a very > similar proposal to this one. > > Most of the discussion on list was really centered around the fact that > nobody like the proposed ?? or .? spellings, and nobody could see around > that fact to consider whether the feature itself was intrinsically valuable. > (This is why the PEP doesn't commit to a syntax.) Also, as unfortunate side > effect of a miscommunication, about 95% of the posts on this PEP were > written _before_ I submitted a complete draft and so most of the > conversation was arguing about a straw man. > > David Mertz: >> >> The idea is that we can easily have both "regular" behavior and None >> coalescing just by wrapping any objects in a utility class... and WITHOUT >> adding ugly syntax. I might have missed some corners where we would want >> behavior wrapped, but those shouldn't be that hard to add in principle. > > > The biggest problem with a wrapper in practice is that it has to be > unwrapped before it can be passed to any other code that doesn't know how to > handle it. E.g. if you want to JSON encode an object, you need to unwrap all > of the NullCoalesce objects because the json module wouldn't know what to do > with them. The process of wrapping and unwrapping makes the resulting code > more verbose than any existing syntax. >> >> How much of the time is a branch of the None check a single fallback value >> or attribute access versus how often a suite of statements within the >> not-None branch? >> >> I definitely check for None very often also. I'm curious what the >> breakdown is in code I work with. > > There's a script in the PEP-505 repo that can you help you identify code > that could be written with the proposed syntax. (It doesn't identify blocks > that would not be affected, so this doesn't completely answer your > question.) > > https://github.com/mehaase/pep-0505/blob/master/find-pep505.py > > The PEP also includes the results of running this script over the standard > library. > > On Sat, Sep 10, 2016 at 1:26 PM, Guido van Rossum <gu...@python.org> wrote: >> >> The way I recall it, we arrived at the perfect syntax (using ?) and >> semantics. The issue was purely strong hesitation about whether >> sprinkling ? all over your code is too ugly for Python, and in the end >> we couldn't get agreement on *that*. Another problem is PEP 505 -- it >> is full of discussion but its specification is unreadable due to the >> author's idea to defer the actual choice of operators and use a >> strange sequence of unicode characters instead. >> >> If someone wants to write a new, *short* PEP that defers to PEP 505 >> for motivation etc. and just writes up the spec for the syntax and >> semantics we'll have a better starting point. IMO the key syntax is >> simply one for accessing attributes returning None instead of raising >> AttributeError, so that e.g. `foo?.bar?.baz` is roughly equivalent to >> `foo.bar.baz if (foo is not None and foo.bar is not None) else None`, >> except evaluating foo and foo.bar only once. >> >> On Sat, Sep 10, 2016 at 10:14 AM, Random832 <random...@fastmail.com> >> wrote: >> > On Sat, Sep 10, 2016, at 12:48, Stephen J. Turnbull wrote: >> >> I forget if Guido was very sympathetic to null-coalescing operators, >> >> given somebody came up with a good syntax. >> > >> > As I remember the discussion, I thought he'd more or less conceded on >> > the use of ? but there was disagreement on how to implement it that >> > never got resolved. Concerns like, you can't have a?.b return None >> > because then a?.b() isn't callable, unless you want to use a?.b?() for >> > this case, or some people wanted to have "a?" [where a is None] return a >> > magic object whose attribute/call/getitem would give no error, but that >> > would have to keep returning itself and never actually return None for >> > chained operators. >> > _______________________________________________ >> > Python-ideas mailing list >> > Python-ideas@python.org >> > https://mail.python.org/mailman/listinfo/python-ideas >> > Code of Conduct: http://python.org/psf/codeofconduct/ >> >> >> >> -- >> --Guido van Rossum (python.org/~guido) >> _______________________________________________ >> Python-ideas mailing list >> Python-ideas@python.org >> https://mail.python.org/mailman/listinfo/python-ideas >> Code of Conduct: http://python.org/psf/codeofconduct/ > > -- --Guido van Rossum (python.org/~guido) _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
