On Sun, May 02, 2021 at 04:30:38PM -0400, Eric V. Smith wrote:
[I suggested]
> >Better to invent a new format code, which I'm going to spell as 'X' for
> >lack of something better, that maps a format specifier to every
> >element of any iterable (not just generator comprehensions):
> >
> > f'{row:X>8.3f} | {sum(row):>8.3f}'
> >
> >meaning, format each element of row with `>8.3f`.
>
> I'm completely opposed to all of this, but I'll note that you don't want
> the thing that gives instructions to the f-string mechanism to be part
> of the format specifier, you'd want it to be a conversion flag like !r
> and !s. The format spec is reserved for the object being formatted. The
> way this is specified, you'd either have to change the f-string
> mechanics to start interpreting format specs, or have every iterable
> understand what "X" means.
Good point! Thank you.
> For example, "X" is already understood by datetime as part of its format
> spec "language":
>
> >>> f'{datetime.now() - timedelta(days=3):X days ago it was a %A}'
> 'X days ago it was a Thursday'
>
> I don't think you'd want f-strings to hijack that expression because it
> starts with "X". Better to do something like:
>
> f'{row!X:>8.3f} | {sum(row):>8.3f}'
That makes more sense.
> But I'll reiterate that I'm opposed. Sometimes you just need to do the
> formatting outside of an f-string. Terseness shouldn't be the ultimate goal.
I agree with your general observation, but in the specific case of "do
this to every element of this iterable", I think that's common enough
that we should consider building it into the mini-languages used by
format and f-strings.
Python is an extremely readable language, and it is possible to be too
terse as well as too verbose. Not everything needs to be a one-liner
single expression. But if you see boilerplate code like:
for each element of spam:
format element in the exact same way
it makes sense to consider abstracting it into a single operation:
format each element of spam
--
Steve
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