[Python-ideas] Briefer string format

[Chris Angelico]

On Mon, Aug 3, 2015 at 1:37 AM, Eric V. Smith <eric at trueblade.com> wrote:
> There's currently no way around this. You could try putting a space
> between the left braces, but that fails with IndentationError:
>
>>>> f'expr={ {x: y for x, y in [(1, 2), (3, 4)]}}'
>   File "<fstring>", line 1
>     {x: y for x, y in [(1, 2), (3, 4)]}
>     ^
> IndentationError: unexpected indent
>
> In the PEP I'm going to specify that leading spaces are skipped in an
> expression. So that last example will now work:
>
>>>> f'expr={ {x: y for x, y in [(1, 2), (3, 4)]}}'
> 'expr={1: 2, 3: 4}'
>
> Note that the right braces in that last example aren't interpreted as a
> doubled '}'. That's because the first one is part of the expression, and
> the second one ends the expression. The only time doubling braces
> matters is inside the string literal portion of an f-string.

Sounds good. And even though your }} is perfectly valid, I'd recommend
people use spaces at both ends:

>>> f'expr={ {x: y for x, y in [(1, 2), (3, 4)]} }'
'expr={1: 2, 3: 4}'

which presumably would be valid too. It's a narrow enough case
(expressions beginning or ending with a brace) that the extra spaces
won't be a big deal IMO.

ChrisA