(Our posts crossed, to some extent.) On Mon, Jul 20, 2015 at 8:41 PM, Steve Dower <Steve.Dower@microsoft.com> wrote:
Eric V. Smith wrote:
On 07/20/2015 01:25 PM, Guido van Rossum wrote:
Perhaps surprisingly, I find myself leaning in favor of the f'...{var}...' form. It is explicit in the variable name.
[...]
So the idea is that f'x:{a.x} y:{y}' would translate to bytecode that does: 'x:{a.x} y:{y}'.format(a=a, y=y)
Correct?
That's exactly what I had in mind, at least. Indexing is supported in format strings too, so f'{a[1]}' also becomes '{a[1]}'.format(a=a), but I don't think there are any other strange cases here. I would vote for f'{}' or f'{0}' to just be a SyntaxError.
+1 on that last sentence. But I prefer a slightly different way of implementing (see my reply to Eric).
I briefly looked into how this would be implemented and while it's not quite trivial/localized, it should be relatively straightforward if we don't allow implicit merging of f'' strings. If we wanted to allow implicit merging then we'd need to touch more code, but I don't see any benefit from allowing it at all, let alone enough to justify seriously messing with this part of the parser.
Not sure what you mean by "implicit merging" -- if you mean literal concatenation (e.g. 'foo' "bar" == 'foobar') then I think it should be allowed, just like we support mixing quotes and r''. -- --Guido van Rossum (python.org/~guido)