On Tue, Oct 02, 2018 at 08:27:03PM -0400, Eric V. Smith wrote:
> Here’s the idea: for f-strings, we add a !d conversion operator, which
> is superficially similar to !s, !r, and !a. The meaning of !d is:
> produce the text of the expression (not its value!),
I SO WANT THIS AS A GENERAL FEATURE, not just for f-strings, it hurts.
Actually what I want is an executable object (a function?) which has the
AST and text of the expression attached. If putting this into f-strings
is a first step towards getting this thunk-like thing, then I don't
need to read any further, I'm +10000 :-)
But considering the proposal as you give it:
> followed by an
> equal sign, followed by the repr of the value of the expression. So:
>
> value = 10
> s = 'a string!'
> print(f'{value!d}')
> print(f'next: {value+1!d}')
> print(f'{s!d}')
>
> produces:
>
> value=10
> next: value+1=11
> s='a string!'
I can see lots of arguments about whether the equals sign should have
spaces around it.
Maybe !d for no spaces and !D for spaces?
print(f'next: {value+1!d}')
print(f'next: {value+1!D}')
would print
next: value+1=11
next: value+1 = 11
> I’m not proposing this for str.format(). It would only really make sense
> for named arguments, and I don’t think
> print('{value!d}'.format(value=value) is much of a win.
I'm not so sure that it only makes sense for named arguments. I think it
works for arbitrary expressions too:
f'{len("NOBODY expects the Spanish Inquisition!")!d}'
ought to return
'len("NOBODY expects the Spanish Inquisition!")=39'
which I can see being very useful in debugging expressions.
This is perhaps the first time I've been excited and enthusiastic about
f-strings. A definite +1 on this.
--
Steve
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