[Python-Dev] transitioning from % to {} formatting

Barry Scott barry at barrys-emacs.org
Sun Oct 4 14:10:57 CEST 2009

On 1 Oct 2009, at 10:37, M.-A. Lemburg wrote:

> Eric Smith wrote:
>> Martin v. Löwis wrote:
>>> Steven Bethard wrote:
>>>> There's a lot of code already out there (in the standard library  
>>>> and
>>>> other places) that uses %-style formatting, when in Python 3.0 we
>>>> should be encouraging {}-style formatting.
>>> I don't agree that we should do that. I see nothing wrong with using
>>> % substitution.
> I agree with Martin.
> Both approaches have their ups and downs, but forcing users to move
> from %-formatting to .format()-formatting will just frustrate them:
> having to convert several thousand such (working) uses in their code
> with absolutely no benefit simply doesn't look like a good way to
> spend your time.

I agree you cannot force the move to {} format. There are programs that
expose the %(name)s in user interfaces for customisation.

> In addition to the code changes, such a move would also render
> existing translations of the %-formatted string templates useless.

Speaking of translation support has xgettext been updated to support {}?
It is a life saver to have xgettext report that "This %s and %s" is not


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