[Python-ideas] Binary f-strings

[Guido van Rossum]

Of course that would still leave the door open for struct.pack support
(maybe recognized by having the string start with <,=, > or @). Pro:
everybody who currently uses struct.pack will love it. Con: the struct.pack
mini-language is pretty inscrutable if you don't already know it. (And no,
I don't propose to invent a different mini-language -- it's just easier to
figure out where to find docs for this when the code explicitly imports the
struct module.)

On Wed, Oct 7, 2015 at 10:53 AM, Eric V. Smith <eric at trueblade.com> wrote:

> On 10/07/2015 12:25 PM, Guido van Rossum wrote:
> > I think bf'...' should be compared to b'...' % rather than to f'...'.
> > IOW bf'...' is to f'...' as b'...'% is to '...'%.
>
> I'm leaning this way, at least in the sense of "there's a fixed number
> of known types supported, and there's no extensible protocol involved.
>
> Eric.
>
> >
> > On Wed, Oct 7, 2015 at 5:34 AM, Andrew Barnert <abarnert at yahoo.com
> > <mailto:abarnert at yahoo.com>> wrote:
> >
> >     On Oct 7, 2015, at 04:35, Nick Coghlan <ncoghlan at gmail.com
> >     <mailto:ncoghlan at gmail.com>> wrote:
> >     >
> >     >> On 4 October 2015 at 08:25, Andrew Barnert <abarnert at yahoo.com
> <mailto: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 <http://python.org/~guido>)
> >
> >
> > _______________________________________________
> > Python-ideas mailing list
> > Python-ideas at python.org
> > https://mail.python.org/mailman/listinfo/python-ideas
> > Code of Conduct: http://python.org/psf/codeofconduct/
> >
>
>


-- 
--Guido van Rossum (python.org/~guido)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20151007/f33de49f/attachment.html>