Here’s another advantage of having a separate function that I didn’t see
acknowledged in the PEP:
If strict behavior is a better default for a zip-like function than
non-strict, then choosing a new function would let you realize that better
default. In contrast, by adding a new argument to the existing function,
the function you use will forever have the less preferred default.
In terms of what is a better default, I would say strict is better because
errors can’t pass silently: If errors occur, you can always change the
flag. But you would be doing that explicitly.
—Chris
On Fri, May 15, 2020 at 6:57 AM Paul Ganssle <p...@ganssle.io> wrote:
> I'm on the fence about using a separate function vs. a keyword argument
> (I think there is merit to both), but one thing to note about the
> separate function suggestion is that it makes it easier to write
> backwards compatible code that doesn't rely on version checking. With
> `itertools.zip_strict`, you can do some graceful degradation like so:
>
> try:
> from itertools import zip_strict
> except ImportError:
> zip_strict = zip
>
> Or provide fallback easily:
>
> try:
> from itertools import zip_strict
> except ImportError:
> def zip_strict(*args):
> yield from zip(*args)
> for arg in args:
> if next(arg, None):
> raise ValueError("At least one input terminated early.")
>
> There's an alternate pattern for the kwarg-only approach, which is to
> just try it and see:
>
> try:
> zip(strict=True)
> HAS_ZIP_STRICT = True
> except TypeError:
> HAS_ZIP_STRICT = False
>
> But I would say it's considerably less idiomatic.
>
> Just food for thought here. In the long run this doesn't matter, because
> eventually 3.9 will fall out of everyone's support matrices and these
> workarounds will become obsolete anyway.
>
> Best,
> Paul
>
> On 5/15/20 5:20 AM, Stephen J. Turnbull wrote:
> > Brandt Bucher writes:
> >
> > > Still agreed. But I think they would be *better* served by the
> > > proposed keyword argument.
> > >
> > > This whole sub-thread of discussion has left me very confused. Was
> > > anything unclear in the PEP's phrasing here?
> >
> > I thought it was quite clear. Those of us who disagree simply
> > disagree. We prefer to provide it as a separate function. Just move
> > on, please; you're not going to convince us, and we're not going to
> > convince you. Leave it to the PEP Delegate or Steering Council.
> >
> > > I wouldn't confuse "can" and "should" here.
> >
> > You do exactly that in arguing for your preferred design, though.
> >
> > We could implement the strictness test with an argument to the zip
> > builtin function, but I don't think we should. I still can't think of
> > a concrete use case for it from my own experience. Of course I
> > believe concrete use cases exist, but that introspection makes me
> > suspicious of the claim that this should be a builtin feature, with
> > what is to my taste an ugly API.
> >
> > Again, I don't expect to convince you, and you shouldn't expect to
> > convince me, at least not without more concrete and persuasive use
> > cases than I've seen so far.
> >
> > Steve
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