[Python-Dev] PEP 461 - Adding % and {} formatting to bytes

[Brett Cannon]

On Thu, Jan 16, 2014 at 4:56 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:

>
> On 16 Jan 2014 17:53, "Ethan Furman" <ethan at stoneleaf.us> wrote:
> >
> > On 01/15/2014 06:45 AM, Brett Cannon wrote:
> >>
> >>
> >> This is why I have argued that if you specify it as "if there is a
> format spec specified, then the return value from
> >> calling __format__() will have str.decode('ascii', 'strict') called on
> it" you get the support for the various
> >> number-specific format specs for free.
> >
> >
> > It may work like this under the hood, but it's an implementation detail.
>  Since the numeric format codes will call int, index, or float on the
> object (to handle subclasses), we could then call __format__ on the
> resulting int or float to do the heavy lifting; but since __format__ on
> anything else would never be called I don't want to give that impression.
>
> I have a different proposal: let's *just* add mod formatting to bytes, and
> leave the extensible formatting system as a text only operation.
>
> We don't really care if bytes supports that method for version
> compatibility purposes, and the deliberate flexibility of the design makes
> it hard to translate into the binary domain.
>
> So let's just not provide that - let's accept that, for the binary domain,
> printf style formatting is just a better fit for the job :)
>

Or PEP 460 for bytes.format() and PEP 461 for %.

-Brett


> Cheers,
> Nick.
>
> >
> >
> >> It also means if you pass in a string that you just want the strict
> ASCII bytes
> >> of then you can get it with {:s}.
> >
> >
> > This isn't going to happen.  If the user wants a string to be in the
> byte stream, it has to either be a bytes literal or explicitly encoded [1].
> >
> > --
> > ~Ethan~
> >
> > [1] Apologies if this has already been answered.  I wanted to make sure
> I responded to all the ideas/objects, and I may have responded more than
> once to some.  It's been a long few threads.  ;)
> >
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