88 lines
2.9 KiB
Python
88 lines
2.9 KiB
Python
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# vat.py - functions for handling Irish 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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"""VAT (Irish VAT number).
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The Irish VAT number consists of 8 digits. The last digit is a check
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letter, the second digit may be a number, a letter, "+" or "*".
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>>> validate('IE 6433435F')
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'6433435F'
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>>> validate('6433435E') # 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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>>> validate('8D79739I') # old style number
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'8D79739I'
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>>> validate('8?79739J') # incorrect old style
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Traceback (most recent call last):
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...
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InvalidFormat: ...
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"""
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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('IE'):
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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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alphabet = 'WABCDEFGHIJKLMNOPQRSTUV'
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number = (7 - len(number)) * '0' + number
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return alphabet[sum((8 - i) * int(n) for i, n in enumerate(number)) % 23]
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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 not number[:1].isdigit() or not number[2:7].isdigit():
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raise InvalidFormat()
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if len(number) != 8:
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raise InvalidLength()
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if number[:7].isdigit():
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# new system
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if number[-1] != calc_check_digit(number[:-1]):
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raise InvalidChecksum()
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elif number[1] in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ+*':
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# old system
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if number[-1] != calc_check_digit(number[2:-1] + number[0]):
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raise InvalidChecksum()
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else:
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raise InvalidFormat()
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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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