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

[Guido van Rossum]

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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-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)