On Wed, Jul 22, 2015 at 9:04 AM, Mike Miller <python-ideas@mgmiller.net> wrote:
Second, there is an inconsistency in quoting of string dictionary keys. That's unfortunate, but the way format currently works. Since f'' will be implemented on top, is not the quoting issue orthogonal to it?
So I guess the question is: Does f"..." have to be implemented on top of str.format, or should it be implemented separately on top of object.__format__? The two could be virtually indistinguishable anyway. Something like this: loc = "world" print(f"Hello, {loc}!") # becomes loc = "world" print("Hello, "+loc.__format__("")+"!") # maybe with the repeated concat optimized to a join With that, there's no particular reason for the specifics of .format() key lookup to be retained. Want full expression syntax? Should be easy - it's just a matter of getting the nesting right (otherwise it's a SyntaxError, same as (1,2,[3,4) would be). Yes, it'll be a bit harder for simplistic parsers to work with, but basically, this is no longer a string literal - it's a compact syntax for string formatting and concatenation, which is something I can definitely get behind. REXX allowed abuttal for concatenation, so you could write something like this: msg = "Hello, "loc"!" Replace those interior quotes with braces, and you have an f"..." string. It's not a string, it's an expression, and it can look up names in its enclosing scope. Describe it alongside list comprehensions, lambda expressions, and so on, and it fits in fairly nicely. No longer -0.5 on this. ChrisA