[Python-3000] Implementing % formatting in terms of str.format()

[Eric Smith]

Understood.  Maybe I'll just use this technique to implement %b, and 
leave everything else alone.  I'll investigate.

Guido van Rossum wrote:
> I think there are too many risks with this approach, especially given
> that we're keeping % formatting mainly for backwards compatibility
> reasons. There will inevitably be corner cases where the conversion
> doesn't work exactly the same way as the old code or where the
> conversion is wrong for whatever reason, and it would be quite painful
> to change back.
> 
> If 2.6 can't support %b, so be it.
> 
> On Wed, Apr 9, 2008 at 4:54 PM, Eric Smith
> <eric+python-dev at trueblade.com> wrote:
>> I'm working on issue 2416, adding %b to % formatting
>>  (http://bugs.python.org/issue2416).  It's really quite a pain,
>>  especially in 2.6 with int and long and str and unicode.
>>
>>  I'm contemplating just making % formatting compute a new format string
>>  and call str.format (or obj.__format__, or something appropriate).  But
>>  before I proceed, I thought I'd ask and see if this really offends
>>  anyone.  By implementing % in terms of str.format, I hope to be able to
>>  delete a lot of the duplication in the formatting code, but I haven't
>>  checked yet to see what's possible.  The real impetus is issue 2416, though.
>>
>>  About the only downside I see is that str.format is somewhat slower than
>>  %, but I can probably get around most of this by directly calling
>>  int.__format__, float.__format__, etc.  Other than misleading
>>  microbenchmarks, I've never really compared the difference, though.
>>
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> 
> 
>