Python JSON serialize a Decimal object

Simplejson 2.1 and higher has native support for Decimal type:

>>> json.dumps(Decimal('3.9'), use_decimal=True)
'3.9'

Note that use_decimal is True by default:

def dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True,
    allow_nan=True, cls=None, indent=None, separators=None,
    encoding='utf-8', default=None, use_decimal=True,
    namedtuple_as_object=True, tuple_as_array=True,
    bigint_as_string=False, sort_keys=False, item_sort_key=None,
    for_json=False, ignore_nan=False, **kw):

So:

>>> json.dumps(Decimal('3.9'))
'3.9'

Hopefully, this feature will be included in standard library.