[Python-ideas] Binary f-strings

[Guido van Rossum]

I think bf'...' should be compared to b'...' % rather than to f'...'. IOW
bf'...' is to f'...' as b'...'% is to '...'%.

On Wed, Oct 7, 2015 at 5:34 AM, Andrew Barnert <abarnert at yahoo.com> wrote:

> On Oct 7, 2015, at 04:35, Nick Coghlan <ncoghlan at gmail.com> wrote:
> >
> >> On 4 October 2015 at 08:25, Andrew Barnert <abarnert at yahoo.com> wrote:
> >> Nick's suggestion of having it do %-formatting makes sense. Yes, it
> means
> >> that {count:03} is an error and you need '{count:03d}', which is
> >> inconsistent with f-strings. But that seems like a much less serious
> problem
> >> than bytes formatting not being able to handle bytes.
> >
> > Exactly, if someone is mistakenly thinking
> > bf"{header}{content}{footer}" is equivalent to
> > f"{header}{content}{footer}".encode(), they're likely to get immediate
> > noisy errors when they start trying to format fields.
>
> Except that multiple people in this thread are saying that'd exactly what
> it should mean (which I think is a very bad idea).
>
> > The parallel I'd attempt to draw is that:
> >
> >    f"{header}{content}{footer}" is to "{}{}{}".format(header, content,
> footer)
> >
> > as:
> >
> >    bf"{header:b}{content:b}{footer:b}" would be to b"%b%b%b" %
> > (header, content, footer)
> >
> > To make the behaviour clearer in the latter case, it may be reasonable
> > to *require* an explicit field format code, since that corresponds
> > more closely to the mandatory field format codes in mod-formatting.
>
> Are you suggestive that if a format specifier is given, it must include
> the format code (which seems perfectly reasonable to me--guessing that :3
> means %3b is likely to be wrong more often than it's right…), or that a
> format specifier must always be given, with no default to :b (which seems
> more obtrusive and solves less of a problem).
>
>


-- 
--Guido van Rossum (python.org/~guido)
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