
On Mon, Aug 17, 2015 at 1:26 PM, Eric V. Smith <eric@trueblade.com> wrote:
[...] I think it would be possible to create a version of this that works for both i18n and regular interpolation. I think the open issues are:
1. Barry wants the substitutions to look like $identifier and possibly ${identifier}, and the PEP 498 proposal just uses {}.
2. There needs to be a way to identify interpolated strings and i18n strings, and possibly combinations of those. This leads to PEP 501's i- and iu- strings.
3. A way to enforce identifiers-only, instead of generalized expressions.
In an off-list message to Barry and Nick I came up with the same three points. :-) I think #2 is the hard one (unless we adopt a solution like Yury just proposed where you can have an arbitrary identifier in front of a string literal).
4. We need a "safe substitution" mode for str.format_map_simple (from above).
#1 is just a matter of preference: there's no technical reason to prefer {} over $ or ${}. We can make any decision here. I prefer {} because it's the same as str.format.
#2 needs to be decided in concert with the tooling needed to extract the strings from the source code. The particular prefixes are up for debate. I'm not a big fan of using "u" to have a meaning different from it's current "do nothing" interpretation in 3.5. But really any prefixes will do, if we decide to use string prefixes. I think that's the question: do we want to distinguish among these cases using string prefixes or combinations thereof?
#3 is doable, either at runtime or in the tooling that does the string extraction.
#4 is simple, as long as we always turn it on for the localized strings.
Personally I can go either way on including i18n. But I agree it's beginning to sound like i18n is just too complicated for PEP 498, and I think PEP 501 is already too complicated. I'd like to make a decision on this one way or the other, so we can move forward.
What's the rush? There's plenty of time before Python 3.6.
[...] > The understanding here is that there are these new types of tokens: > F_STRING_OPEN for f'...{, F_STRING_MIDDLE for }...{, F_STRING_END
for
> }...', and I suppose we also need F_STRING_OPEN_CLOSE for f'...'
(i.e.
> not containing any substitutions). These token types can then be
used in
> the grammar. (A complication would be different kinds of string
quotes;
> I propose to handle that in the lexer, otherwise the number of > open/close token types would balloon out of proportions.)
This would save a few hundred lines of C code. But a quick glance at
the
lexer and I can't see how to make the opening quotes agree with the closing quotes.
The lexer would have to develop another stack for this purpose.
I'll give it some thought.
Eric.
-- --Guido van Rossum (python.org/~guido)