new_contents: # 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'
  """
  
  import re
  
  from stdnum.exceptions import *
  from stdnum.util import clean
  
  
  # regular expression for matching ITINs
  _itin_re = re.compile('^(?P<area>[0-9]{3})-?(?P<group>[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):
      """Checks to see if the number provided 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):
      """Checks to see if the number provided is a valid ITIN. This checks
      the length, groups and formatting if it is present."""
      try:
          return bool(validate(number))
      except ValidationError:
          return False
  
  
  def format(number):
      """Reformat the passed number to the standard format."""
      if len(number) == 9:
          number = number[:3] + '-' + number[3:5] + '-' + number[5:]
      return number
  
subject: Add a United States ITIN module