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

Nick Coghlan ncoghlan at gmail.com
Thu Jan 16 10:56:41 CET 2014

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 :)


>> 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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