Underscores in Python numbers

[Steven D'Aprano]

On Sat, 19 Nov 2005 13:08:57 -0500, Peter Hansen wrote:

> Umm... in other words, "the underscore is under-used so let's assign 
> some arbitrary meaning to it" (to make the language more like Perl 
> perhaps?).

+1

I *really* don't like the idea of allowing underscores in numeric
literals. Firstly, for aesthetic reasons: I think 123_456 is seriously
ugly. Secondly, for pragmatic reasons, I think it is too easy to mistype
as 123-456. I know that Python can't protect you from typing 9-1 instead
of 901, but why add special syntax that makes that sort of error MORE
common?)

> Or maybe one should instead interpret this as "numeric literals need 
> more bells and whistles, and I don't care which of these two we add, but 
> we have to do *something*!". :-)

-1

That's a tad unfair. Dealing with numeric literals with lots of digits is
a real (if not earth-shattering) human interface problem: it is hard for
people to parse long numeric strings. In the wider world outside of IT,
people deal with long numeric digits by grouping. This is *exceedingly*
common: mathematicians do it, economists do it, everybody who handles long
numeric literals does it *except* computer language designers.

Depending on personal preference and context, we use any of comma, period,
dash or space as a separator. Underscore is never used. Of these, the
comma clashes with tuples, the period opens a rather large can of worms
vis-a-vis internationalisation, and the dash clashes with the minus sign.
Allowing spaces to group digits is subtle but effective, doesn't clash
with other syntax, and is analogous to string concatenation.

I don't believe it is either practical or desirable for a computer
language to accept every conceivable digit separator in literals. If you
need full support for internationalised numbers, that should go into a
function. But the question of including a digit separator for numeric
literals does solve a real problem, it isn't just meaningless bells and
whistles.

Likewise, base conversion into arbitrary bases is not, in my opinion,
common enough a task that support for it needs to be built into the syntax
for literals. If somebody cares enough about it, write a module to handle
it and try to get it included with the Python standard modules.


-- 
Steven.