The original proposal was well-received but it didn't make provisions to handle str.format().
Here is the revised proposal. Only the last paragraph is new.
Raymond
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Mark Dickinson's decimal 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)'
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 localeconv():
{
'decimal_point': '.',
'grouping': [3, 0],
'negative_sign': '-',
'positive_sign': '',
'thousands_sep': ','}
The would let you store several locales using localeconv() and use them at will, thus solving the global variable and threading
problems with locale:
import locale
loc = locale.getlocale() # get current locale
locale.setlocale(locale.LC_ALL, 'de_DE')
DE = locale.localeconv()
locale.setlocale(locale.LC_ALL, 'en_US')
US = locale.localeconv()
locale.setlocale(locale.LC_ALL, loc) # restore saved locale
. . .
format(x, '8,.f', DE)
format(y, '8,d', US)
It also lets you write your own conventions on the fly:
DEBUG = dict(thousands_sep='_') # style for debugging
EXTERN = dict(thousands_sep=',') # style for external display
. . .
format(x, '8.1f', DEBUG)
format(y, '8d', EXTERN)
The dictionaries can be registered for use with the mini-formatting language:
locale.setlocale(locale.LC_ALL, 'en_US')
str.format.register(US=locale.localeconv())
str.format.register(HY=dict(thousands_sep='-'))
. . .
'Nigerian President will forward {0:,d!US} to your account'.format(10000000)
format(y, ',d!HY')
format(z, ',d!US')