[Python-ideas] Customizing format()
steve at pearwood.info
Wed Mar 18 12:45:11 CET 2009
On Wed, 18 Mar 2009 11:25:42 am Raymond Hettinger wrote:
> Mark Dickinson's test code suggested a good, extensible approach to
> the problem. Here's the idea in a nutshell:
> format(value, format_spec='', conventions=None)
> 'calls value.__format__(format_spec, conventions)'
For what was supposed to be a nice, simple way of formatting numbers, it
sure became confusing. So thank you for the nutshell.
I like this idea, especially if it means we can simplify the
format_spec. Can we have the format_spec in a nutshell too?
> Where conventions is an optional dictionary with formatting control
> values. Any value object can accept custom controls, but the names
> for standard ones would be taken from the standards provided by
> 'decimal_point': '.',
> 'grouping': [3, 0],
> 'negative_sign': '-',
> 'positive_sign': '',
> 'thousands_sep': ','}
Presumably we value compatibility with localeconv()? If not, then
perhaps a better name for 'thousands_sep' is 'group_sep', on account
that if you group by something other than 3 it won't represent
Would this allow you to format a float like this?
1,234,567.89012 34567 89012
(group by threes for the integer part, and by fives for the fractional
part). Or is that out-of-scope for this proposal?
+1 for a conventions dict. Good plan!
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