On Thu, Mar 27, 2014 at 10:55 AM, Ethan Furman <et...@stoneleaf.us> wrote:
> On 03/27/2014 10:29 AM, Guido van Rossum wrote:
>
>>
>> I also don't understand why we can't use %b instead of %s. AFAIK %b
>> currently doesn't mean anything and I somehow don't
>> expect we're likely to add it for other reasons (unless there's a
>> proposal I'm missing?). Just like we use %a instead of
>> %r to remind people that it's not quite the same (since it applies
>> .encode('ascii', 'backslashreplace')), shouldn't we
>> use anything *but* %s to remind people that that is also not the same
>> (not at all, in fact)? The PEP's argument against
>> %b ("rejected as not adding any value either in clarity or simplicity")
>> is hardly a good reason.
>>
>
> The biggest reason to use %s is to support a common code base for 2/3
> endeavors.
But it's mostly useless for that purpose. In Python 2, in practice %s
doesn't mean "string". It means "use the default formatting just as if I
was using print." And in theory it also means that -- in fact "call
__str__()" is the formal definition, and print is also defined as using
__str__, and this is all intentional. (I also intended __str__ to be
*mostly* the same as __repr__, with a specific exception for the str type
itself. In practice some frameworks have adopted a different
interpretation, making __repr__ produce something *more* "user friendly"
than __str__ but including newlines, because some people believe the main
use case for __repr__ is the interactive prompt. I believe this causes
problems for some *other* uses of __repr__, such as for producing an
"unambiguous" representation useful for e.g. logging -- but I don't want to
be too bitter about it. :-)
The biggest reason to not include %b is that it means binary number in
> format(); given that each type can invent it's own mini-language, this
> probably isn't a very strong argument against it.
>
Especially since I can't imagine the spelling in format() includes '%'.
> I have moderate feelings for keeping %s as a synonym for %b for backwards
> compatibility with Py2 code (when it's appropriate).
>
I think it's mere existence (with the restrictions currently in the PEP)
would cause more confusion than that is worth.
--
--Guido van Rossum (python.org/~guido)
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