On 2020-05-06 12:48 p.m., Christopher Barker wrote:
On Tue, May 5, 2020 at 5:43 PM Steven D'Aprano <steve@pearwood.info> wrote:
Christopher's quoting is kinda messed up and I can't be bothered fixing
it, sorry, so you'll just have to guess who said what :-)

Ideally, we are evaluating ideas independently of who expressed them, so I'll pretend I did that on purpose :-)

First: really people, it's all been said. I think we all (and I DO include myself in that) have fallen into the trap that "if folks don't agree with me, I must not have explained myself well enough" -- but in this case, we actually do disagree. And not really on the facts, just on the relative importance.

But since, I apparently did not explain myself well enough in this case:
> no -- but we could (and I think should) have a ternary flag, so that
> zip_longest becomes unnecessary. And we'd never get to eight combinations:
> you can't have longest and shortest behavior at the same time!

A ternary flag of strict = True, False or what?

Come on:

ternary: having three elements, parts, or divisions (https://www.merriam-webster.com/dictionary/ternary)

did you really not know that? (and "flag" does not always mean "boolean flag", even thoughit often does (https://techterms.com/definition/flag) )

(by the way, I'm posting those references because I looked them up to make sure I wasn't using terms incorrectly)

This has been proposed multiple times on this list:

a flag that takes three possible values: "shortest" | "longest" | "equal" (defaulting to shortest of course). Name to be bikeshed later :-)
(and enum vs string also to be bikeshed later)


how about "length"?

length=True # longest
length=False # shortest (default)
length=None # equal

(altho I still think the "YAGNI function" system would be better >.>)

This demonstrates why the "constant flag" is so often an antipattern. It
doesn't scale past two behaviours. Or you end up with a series of flags:

    zip(*iterators, strict=False, longest=False, fillvalue=None)

I don't think anyone proposed an API like that -- yes, that would be horrid.

There are all sorts of reasons why a ternary flag would not be good, but I do think it should be mentioned in the PEP, even if only as a rejected idea.

But I still like it, 'cause the "flag for two behaviors and another function for the third" seem sliek the worse of all options.

-CHB


--
Christopher Barker, PhD

Python Language Consulting
  - Teaching
  - Scientific Software Development
  - Desktop GUI and Web Development
  - wxPython, numpy, scipy, Cython

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