Localized digits

import re
from django import template
from django.utils import translation
from django.template import defaultfilters

register = template.Library()

LANGUAGE_DIGITS = {
    'ar': u'\u0660\u0661\u0662\u0663\u0664\u0665\u0666\u0667\u0668\u0669',
    'fa': u'\u06f0\u06f1\u06f2\u06f3\u06f4\u06f5\u06f6\u06f7\u06f8\u06f9',
}
digit_re = re.compile('\d')

def i18n_digits(str, lang=None):
    """
    Translate the digits in a string into the digits used in the given
    language. If no language is given, the language code from the current
    language is used. While the input can be a basic string, the output will
    always be unicode.
    """
    uc_str = unicode(str)
    if lang is None:
        lang = translation.get_language()
    digits_table = LANGUAGE_DIGITS.get(lang, None)
    if digits_table is not None:
        def digit_replace(match):
            return digits_table[int(match.group())]
        return digit_re.sub(digit_replace, uc_str)
    else:
        return uc_str
i18n_digits = defaultfilters.stringfilter(i18n_digits)
register.filter('i18n_digits', i18n_digits)