[Python-Dev] PEP-498: Literal String Formatting

Alexander Walters tritium-list at sdamon.com
Tue Aug 11 17:26:38 CEST 2015

On 8/11/2015 11:16, Eric V. Smith wrote:
> On 08/11/2015 11:09 AM, Alexander Walters wrote:
>> This may seam like a simplistic solution to i18n, but why not just add a
>> method to string objects (assuming we implement f-strings) that just
>> returns the original, unprocessed string.  If the string was not an
>> f-string, it just returns self.  The gettext module can be modified, I
>> think trivially, to use the method instead of the string directly.
> You need the original string, in order to figure out what it translates
> to. You need the values to replace into that string, evaluated at
> runtime, in the context of where the string appears. And you need to
> know where in the original (or translated) string to put them.
> The problem is that there's no way to evaluate the values and, before
> they're substituted in to the string, use a different template string
> with obvious substitution points. This is what PEP 501 is trying to do.
> Eric.
I don't understand some of that.  We already trust translators with 
_('foo {bar}').format(bar=bar) to not mess up the {bar} in the string, 
so the that wont change.  Is the issue handing the string back to python 
to be formatted?  Could gettext not make the same AST as an f-string 
would, and hand that back to python?  If you add a method to strings 
that returns the un-f-string-processed version of the string, doesn't 
that make all these problems solvable without pep-501?

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