76 lines
2.5 KiB
Python
76 lines
2.5 KiB
Python
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# ddv.py - functions for handling Slovenian 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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"""ID za DDV (Davčna številka, Slovenian VAT number).
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The DDV number (Davčna številka) is used for VAT (DDV, Davek na dodano
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vrednost) purposes and consist of 8 digits of which the last is a check
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digit.
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>>> validate('SI 5022 3054')
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'50223054'
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>>> validate('SI 50223055') # invalid check digits
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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.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('SI'):
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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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check = (11 - sum((8 - i) * int(n) for i, n in enumerate(number)) % 11)
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# this results in a two-digit check digit for 11 which should be wrong
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return '0' if check == 10 else str(check)
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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() or number.startswith('0'):
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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 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
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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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