On Tue, Oct 20, 2020 at 11:54 PM Steven D'Aprano <st...@pearwood.info> wrote:
> The only advantage, I guess, of f-string like syntax is that the
> variable names can be embedded inside the template string:
>
> f"{path:s} - {errors:d} errors, {%warnings:d}" = line
>
> but I'm not convinced that's actually an advantage. I think I prefer the
> C-style for this.
It's exactly the same advantage that they have as rvalues, and I think
there's more to be said for it than is obvious at first glance.
Consider that patterns might not be nice tidy things like this; they
might be parsing an obscure sequence of tokens (because, let's face
it, a lot of text out there isn't designed well), so your pattern
might be something like:
f"{path}: {errors:d}/{warnings:d}" = line
or even:
f"{acc},{date},{type},{amount:[0-9.]}
{description},{refnum:12s}{reference}" = line
which is only a very slight exaggeration from the "why the bleep
didn't you just use actual CSV" parsing from one of my actual apps.
(Banks. Banks are bizarre.)
> Sometimes we want a 500 gigawatt nuclear fusion reaction; but sometimes
> we just want a AA battery. This is the AA battery of parsing.
>
> Personally, I think people use more AA batteries than 500GW fusion
> reactors :-)
[citation needed] :-)
> > - As others have mentioned: could inject variables into locals()
> > making debugging harder.
>
> I'm dubious about that too. I think it would be better to keep the
> parsing separate from the name binding, and use regular assignment for
> that.
Not sure what the concern with "inject[ing] variables" is. The
f-string has to be a literal - it's not a magic object that you can
assign to and new locals appear.
> Yeah, f-strings might be great, but I don't think they are a good match
> for this functionality.
>
> But I would definitely use the functionality.
>
I'd personally prefer sscanf, myself, but I would use this
functionality if it landed too.
ChrisA
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