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# vat.py - functions for handling Austrian VAT numbers
#
# Copyright (C) 2012 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
"""UID (Umsatzsteuer-Identifikationsnummer, Austrian VAT number).
The Austrian UID is a 9-digit number that starts with a U (optionally
preceded with AT). The last digit is a check digit.
>>> compact('AT U13585627')
'U13585627'
>>> is_valid('U13585627')
True
>>> calc_check_digit('U1358562')
'7'
>>> is_valid('U13585626') # incorrect check digit
False
"""
from stdnum import luhn
from stdnum.util import clean
def compact(number):
"""Convert the number to the minimal representation. This strips the
number of any valid separators and removes surrounding whitespace."""
number = clean(number, ' -./').upper().strip()
if number.startswith('AT'):
number = number[2:]
return number
def calc_check_digit(number):
"""Calculate the check digit. The number passed should not have the
check digit included."""
return str((6 - luhn.checksum(number[1:])) % 10)
def is_valid(number):
"""Checks to see if the number provided is a valid VAT number. This checks
the length, formatting and check digit."""
try:
number = compact(number)
except:
return False
return len(number) == 9 and number[0] == 'U' and \
number[1:].isdigit() and \
calc_check_digit(number[:-1]) == number[-1]
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