[Python-ideas] Format mini-language for lakh and crore

[David Mertz]

I actually didn't know about `locale.format("%d", 10e9, grouping=True)`.
But it's still much less general than having the option in the
f-string/.format() mini-language.  This is really about the formatted
string, not necessarily about the locale.  So, e.g. I'd like to be able to
write:

>>> print(f"In European format x is {x:,.2f}, in Indian format it is
{x:`.2f}")

I don't want the format necessarily to be some pseudo-global setting, even
if it can get stored in thread-locals.  That said, having a locale-aware
symbol for delimiting numbers in the format mini-language would also not be
a bad thing.

On Sun, Jan 28, 2018 at 4:27 PM, Nathaniel Smith <njs at pobox.com> wrote:

> On Sun, Jan 28, 2018 at 5:46 AM, Eric V. Smith <eric at trueblade.com> wrote:
> > If I recall correctly, we discussed this at the time, and the problem
> with
> > locale is that it's not thread safe. I agree that if it were, it would be
> > nice to be able to use it, either with 'n', or in some other mode just
> for
> > grouping.
> >
> > The underlying C setlocale()/localeconv() just isn't very friendly to
> this
> > use case.
>
> POSIX.1-2008 added thread-local locales (say that 3x fast); see
> uselocale(3). This appears to be supported on Linux (since glibc 2.3,
> which is older than all supported enterprise distros), MacOS, and the
> BSDs, but not Windows. OTOH Windows, MacOS, and the BSDs all seem to
> provide the non-standard sprintf_l, which takes an explicit locale to
> use.
>
> So it looks like all mainstream OSes actually make it possible to use
> a specific locale to do arbitrary formatting in a thread-safe way.
>
> -n
>
> --
> Nathaniel J. Smith -- https://vorpus.org
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