94 lines
3.3 KiB
Python
94 lines
3.3 KiB
Python
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# vat.py - functions for handling Bulgarian VAT numbers
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# coding: utf-8
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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 (Идентификационен номер по ДДС, Bulgarian VAT number).
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The Bulgarian VAT (Данък върху добавената стойност) number is either 9
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(for legal entities) or 10 digits (for physical persons, foreigners and
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others) long. Each type of number has it's own check digit algorithm.
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>>> compact('BG 175 074 752')
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'175074752'
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>>> validate('175074752')
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'175074752'
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>>> validate('175074751') # invalid 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.bg import egn, pnf
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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('BG'):
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number = number[2:]
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return number
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def calc_check_digit_legal(number):
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"""Calculate the check digit for legal entities. The number passed
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should not have the check digit included."""
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check = sum((i + 1) * int(n) for i, n in enumerate(number)) % 11
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if check == 10:
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check = sum((i + 3) * int(n) for i, n in enumerate(number)) % 11
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return str(check % 10)
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def calc_check_digit_other(number):
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"""Calculate the check digit for others. The number passed should not
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have the check digit included."""
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weights = (4, 3, 2, 7, 6, 5, 4, 3, 2)
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return str((11 - sum(weights[i] * int(n) for i, n in enumerate(number))) % 11)
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def validate(number):
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"""Checks to see if the number provided is a valid VAT number. This
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checks the length, formatting and check digit."""
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number = compact(number)
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if not number.isdigit():
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raise InvalidFormat()
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if len(number) == 9:
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# 9 digit numbers are for legal entities
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if number[-1] != calc_check_digit_legal(number[:-1]):
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raise InvalidChecksum()
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elif len(number) == 10:
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# 10 digit numbers are for physical persons, foreigners and others
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if not egn.is_valid(number) and not pnf.is_valid(number) and \
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number[-1] != calc_check_digit_other(number[:-1]):
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raise InvalidChecksum()
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else:
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raise InvalidLength()
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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
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checks 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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