[Python-ideas] Rough draft: Proposed format specifier for a thousands separator (discussion moved from python-dev)

[Eric Smith]

Raymond Hettinger wrote:
> 
> [Jim Jewett]
>> Fair enough.  But what does a thousands separator provide that the "n"
>> type doesn't already provide?  (Well, except that n isn't as well
>> known  -- but initially this won't be either.)
> 
> It's nice to be have a non-locale aware alternative so you can say
> explicitly what you want.  This is especially helpful in Guido's example
> where you need to format for a different locale than the one that is
> currently on your machine (i.e. the global state doesn't match the target).

I've always thought that we should have a utility function which formats 
a number based on the same settings that are in the locale, but not 
actually use the locale. Something like:

format_number(123456787654321.123, decimal_point=',', thousands_sep=' ',
               grouping=[4, 3, 2])
 >>> '12 34 56 78 765 4321,123'

That would get rid of threading issues, and you wouldn't have to worry 
about what locales were installed.

I basically have this function in the various formatting routines, it 
just needs to be pulled out and exposed.

>> Do you really want a different type, such as "m" for money?
> 
> I don't but I'm sure someone does.  I did write a money formatter
> sample recipe for the decimal docs so people would have something
> to model from.

This becomes easier with the hypothetical "format_number" routine.

But this is all orthogonal to the str.format() discussion.

Eric.