85 lines
2.6 KiB
Python
85 lines
2.6 KiB
Python
# vkn.py - functions for handling the Turkish tax identification number
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# coding: utf-8
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#
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# Copyright (C) 2019 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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"""VKN (Vergi Kimlik Numarası, Turkish tax identification number).
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The Vergi Kimlik Numarası is the Turkish tax identification number used for
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businesses. The number consists of 10 digits where the first digit is derived
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from the company name.
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More information:
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* https://www.turkiye.gov.tr/gib-intvrg-vergi-kimlik-numarasi-dogrulama
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>>> validate('4540536920')
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'4540536920'
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>>> validate('4540536921')
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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>>> validate('454053692')
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Traceback (most recent call last):
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...
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InvalidLength: ...
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"""
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from __future__ import annotations
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from stdnum.exceptions import *
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from stdnum.util import clean, isdigits
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def compact(number: str) -> str:
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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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return clean(number).strip()
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def calc_check_digit(number: str) -> str:
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"""Calculate the check digit for the specified number."""
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s = 0
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for i, n in enumerate(reversed(number[:9]), 1):
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c1 = (int(n) + i) % 10
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if c1:
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c2 = (c1 * (2 ** i)) % 9 or 9
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s += c2
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return str((10 - s) % 10)
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def validate(number: str) -> str:
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"""Check if the number is a valid Vergi Kimlik Numarası. This checks the
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length and check digits."""
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number = compact(number)
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if not isdigits(number):
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raise InvalidFormat()
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if len(number) != 10:
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raise InvalidLength()
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if calc_check_digit(number) != number[-1]:
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raise InvalidChecksum()
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return number
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def is_valid(number: str) -> bool:
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"""Check if the number is a valid Vergi Kimlik Numarası. This checks the
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length and check digits."""
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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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