# itin.py - functions for handling ITINs
#
# Copyright (C) 2013 Arthur de Jong
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301 USA
"""ITIN (U.S. Individual Taxpayer Identification Number).
The Individual Taxpayer Identification Number is issued by the United
States IRS to individuals who are required to have a taxpayer
identification number but who are not eligible to obtain a Social Security
Number.
It is a nine-digit number that begins with the number 9 and the
fourth and fifth digit are expected to be in a certain range.
>>> validate('912-90-3456')
'912903456'
>>> validate('9129-03456') # dash in the wrong place
Traceback (most recent call last):
...
InvalidFormat: ...
>>> validate('123-45-6789') # wrong start digit
Traceback (most recent call last):
...
InvalidComponent: ...
>>> validate('912-93-4567') # wrong group
Traceback (most recent call last):
...
InvalidComponent: ...
>>> compact('1234-56-789')
'123456789'
>>> format('111223333')
'111-22-3333'
>>> format('123') # unknown formatting is left alone
'123'
"""
import re
from stdnum.exceptions import *
from stdnum.util import clean
# regular expression for matching ITINs
_itin_re = re.compile(r'^(?P[0-9]{3})-?(?P[0-9]{2})-?[0-9]{4}$')
# allowed group digits
_allowed_groups = set((str(x) for x in range(70, 100) if x not in (89, 93)))
def compact(number):
"""Convert the number to the minimal representation. This strips the
number of any valid separators and removes surrounding whitespace."""
return clean(number, '-').strip()
def validate(number):
"""Check if the number is a valid ITIN. This checks the length, groups
and formatting if it is present."""
match = _itin_re.search(clean(number, '').strip())
if not match:
raise InvalidFormat()
area = match.group('area')
group = match.group('group')
if area[0] != '9' or group not in _allowed_groups:
raise InvalidComponent()
return compact(number)
def is_valid(number):
"""Check if the number is a valid ITIN."""
try:
return bool(validate(number))
except ValidationError:
return False
def format(number):
"""Reformat the number to the standard presentation format."""
if len(number) == 9:
number = number[:3] + '-' + number[3:5] + '-' + number[5:]
return number