[Python-3000] More PEP 3101 changes incoming

[Adam Olsen]

On 8/16/07, Paul Moore <p.f.moore at gmail.com> wrote:
> On 16/08/07, Ron Adam <rrr at ronadam.com> wrote:
> > Currently these particular examples aren't the syntax supported by the PEP.
> >  It's an alternative/possibly syntax only if there is enough support for a
> > serial left to right specification pattern as outlined.
>
> Ah, I hadn't realised that. I've been skipping most of the
> discussions, mainly because of the lack of concrete examples :-)
>
> > I think most of developers here are still looking at various details and
> > are still undecided.  Do you have a preference for one or the other yet?
>
> As evidenced by the fact that I failed to notice the difference, I
> can't distinguish the two :-)
>
> All of the examples I've seen are hard to read. As Greg said, I find
> that I have to study the format string, mentally breaking it into
> parts, before I understand it. This is in complete contrast to
> printf-style "%.10s" formats. I'm not at all sure this is anything
> more than unfamiliarity, compounded by the fact that most of the
> examples I see on the list are relatively complex, or edge cases. But
> it's a major barrier to both understanding and acceptance of the new
> proposals.
>
> I'd still really like to see:
>
> 1. A simple listing of common cases, maybe taken from something like
> stdlib uses of %-formats. Yes, most of them would be pretty trivial.
> That's the point!

Seconded!  This discussion needs some grounding.

>
> 2. A *very short* comparison of a few more advanced cases - I'd
> suggest formatting floats as fixed width, 2 decimal places (%5.2f),
> formatting 8-digit hex (%.8X) and maybe a simple date format
> (%Y-%m-%d). Yes, those are the sort of things I consider advanced.
> Examples I've seen in the discussion aren't "advanced" in my book,
> they are "I'll never use that" :-)
>
> 3. Another very short list of a couple of things you can do with the
> new format, which you can't do with the existing % formats.
> Concentrate here on real-world use cases - tabular reports, reordering
> fields for internationalisation, things like that. As a data point,
> I've never needed to centre a field in a print statement. Heck, I
> don't even recall ever needing to specify how the sign of a number was
> printed!
>
> I get the impression that the "clever" new features aren't actually
> going to address the sorts of formatting problems I hit a lot. That's
> fine, I can write code to do what I want, but there's a sense of YAGNI
> about the discussion, because (for example) by the time I need to
> format a centred, max-18, min-5 character number with 3 decimal places
> and the sign hard to the left, I'm also going to want to dot-fill a
> string to 30 characters and insert commas into the number, and I'm
> writing code anyway, so why bother with an obscure format string that
> only does half the job? (It goes without saying that if the format
> string can do everything I want, that argument doesn't work, but then
> we get to the complexity issues that hit regular expressions :-))
>
> Sorry if this sounds a bit skeptical, but there's a *lot* of
> discussion here over a feature I expect to use pretty infrequently.
> 99% of my % formats use nothing more than %s!
>
> Paul.
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-- 
Adam Olsen, aka Rhamphoryncus