[Python-ideas] String interpolation for all literal strings

[Eric V. Smith]

> On Aug 5, 2015, at 3:18 PM, Joseph Jevnik <joejev at gmail.com> wrote:
> 
> raw-strings will not be scanned, correct?

Good question. I would expect them to be scanned. 

Eric. 

> 
>> On Wed, Aug 5, 2015 at 2:56 PM, Eric V. Smith <eric at trueblade.com> wrote:
>> In the "Briefer string format" thread, Guido suggested [1] in passing
>> that it would have been nice if all literal strings had always supported
>> string interpolation.
>> 
>> I've come around to this idea as well, and I'm going to propose it for
>> inclusion in 3.6. Once I'm done with my f-string PEP, I'll consider
>> either modifying it or creating a new (and very similar) PEP.
>> 
>> The concept would be that all strings are scanned for \{ and } pairs. If
>> any are found, then they'd be interpreted in the same was as the other
>> discussion on "f-strings". That is, the expression between the \{ and }
>> would be extracted and searched for conversion characters and format
>> specifiers. The expression would be evaluated, converted if needed, have
>> its __format__ method called, and the resulting string inserted back in
>> to the original string.
>> 
>> Because strings containing \{ are currently valid, we'd have to
>> introduce this feature with a __future__ import statement. How we
>> transition to having this be the default interpretation of strings is up
>> in the air.
>> 
>> Guido privately suggested that it might be nice to also support the 'f'
>> modifier on strings, to give the identical behavior. This way, you could
>> start using the feature without requiring the __future__ import. While
>> I'm not crazy about having two ways to achieve the same thing, I do
>> think it might be nice to support interpolated strings without requiring
>> the __future__ import.
>> 
>> Eric.
>> 
>> 
>> [1] https://mail.python.org/pipermail/python-ideas/2015-August/034928.html
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