75 lines
2.4 KiB
Python
75 lines
2.4 KiB
Python
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# vat.py - functions for handling Austrian VAT numbers
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#
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# Copyright (C) 2012, 2013 Arthur de Jong
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301 USA
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"""UID (Umsatzsteuer-Identifikationsnummer, Austrian VAT number).
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The Austrian UID is a 9-digit number that starts with a U (optionally
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preceded with AT). The last digit is a check digit.
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>>> validate('AT U13585627')
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'U13585627'
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>>> calc_check_digit('U1358562')
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'7'
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>>> validate('U13585626') # incorrect check digit
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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"""
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from stdnum import luhn
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from stdnum.exceptions import *
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from stdnum.util import clean
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def compact(number):
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"""Convert the number to the minimal representation. This strips the
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number of any valid separators and removes surrounding whitespace."""
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number = clean(number, ' -./').upper().strip()
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if number.startswith('AT'):
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number = number[2:]
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return number
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def calc_check_digit(number):
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"""Calculate the check digit. The number passed should not have the
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check digit included."""
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return str((6 - luhn.checksum(number[1:])) % 10)
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def validate(number):
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"""Checks to see if the number provided is a valid VAT number. This checks
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the length, formatting and check digit."""
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number = compact(number)
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if number[:1] != 'U' or not number[1:].isdigit():
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raise InvalidFormat()
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if len(number) != 9:
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raise InvalidLength()
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if calc_check_digit(number[:-1]) != number[-1]:
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raise InvalidChecksum()
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return number
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def is_valid(number):
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"""Checks to see if the number provided is a valid VAT number. This checks
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the length, formatting and check digit."""
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try:
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return bool(validate(number))
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except ValidationError:
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return False
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