On Mon, Jul 5, 2021, 2:40 PM Guido van Rossum <gu...@python.org> wrote:
> FWIW, we could make f-strings properly nest too, like you are proposing > for backticks. It's just that we'd have to change the lexer. But it would > not be any harder than would be for backticks (since it would be the same > algorithm), nor would it be backward incompatible. So this is not an > argument for backticks. > Good point. At some point, I was probably thinking of backticks without a tag, since JS supports this for their f-string like scenario. but if we always require a tag - so long as it's not a prefix already in use (b, f, r, fr, hopefully not forgetting as I type this email in a parking lot...) - then it can be disambiguated using standard quotes. > Separately, should there be a way to *delay* evaluation of the templated > expressions (like we explored in our private little prototype last year)? > I think so, but probably with an explicit marker on *each* deferred expression. I'm in favor of Julia's expression quote, which generally needs to be enclosed in parentheses, but possibly not needed in expression braces (at the risk of looking like a standalone format spec). https://docs.julialang.org/en/v1/manual/metaprogramming/ So this would like x = 42 d = deferred_tag"Some expr: {:(x*2)}" All that is happening here is that this being wrapped in a lambda, which captures any scope lexically as usual. Then per that experiment you mentioned, it's possible to use that scope using fairly standard - or at least portable to other Python implementations - metaprogramming, including the deferred evaluation of the lambda. (No frame walking required!) Other syntax could work for deferring. Maybe backticks, they could be available? 😉 - Jim > -- > --Guido van Rossum (python.org/~guido) > *Pronouns: he/him **(why is my pronoun here?)* > <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/> >
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