Ezio Melotti asked (on #python-dev) why the Decimal constructor doesn't 
accept decimal digits other than 0-9.  As far as I can tell there's no 
good reason for it not to.  Moreover, the standard on which the decimal 
module is based says[1]:

"""It is recommended that implementations also provide additional number 
formatting routines (including some which are locale-dependent), and if 
available should accept non-European decimal digits in strings."""

All other builtin or standard library numeric types already accept such 
digits:

Python 3.2a0 (py3k:74247, Jul 29 2009, 09:28:12) 
[GCC 4.0.1 (Apple Inc. build 5493)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from fractions import Fraction
>>> from decimal import Decimal
>>> x = '\uff11\uff10\uff15\uff18\uff15'
>>> x
'１０５８５'
>>> int(x)
10585
>>> float(x)
10585.0
>>> complex(x)
(10585+0j)
>>> Fraction(x)
Fraction(10585, 1)
>>> Decimal(x)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/dickinsm/python/svn/py3k/Lib/decimal.py", line 548, in 
__new__
    "Invalid literal for Decimal: %r" % value)
  File "/Users/dickinsm/python/svn/py3k/Lib/decimal.py", line 3816, in 
_raise_error
    raise error(explanation)
decimal.InvalidOperation: Invalid literal for Decimal: '１０５８５'

I propose adding support for this in Python 3.2 and (possibly) 2.7.  The 
change would be for input only:  no record of the original form of the 
digits would be kept by the Decimal object itself, so that e.g.,
str(Decimal('１０５８５')) would still be '10585'.

[1] See http://speleotrove.com/decimal/daconvs.html