107 lines
3.3 KiB
Python
107 lines
3.3 KiB
Python
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# kontonr.py - functions for handling Norwegian bank account numbers
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# coding: utf-8
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#
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# Copyright (C) 2018 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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"""Konto nr. (Norwegian bank account number)
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Konto nr. is the country-specific part in Norwegian IBAN codes. The number
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consists of 11 digits, the first 4 are the bank identifier and the last is a
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check digit. This module does not check if the bank identifier exists.
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More information:
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* https://www.ecbs.org/iban/norway-bank-account-number.html
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>>> validate('8601 11 17947')
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'86011117947'
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>>> validate('0000.4090403') # postgiro bank code
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'4090403'
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>>> validate('8601 11 17949') # 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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>>> format('86011117947')
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'8601.11.17947'
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>>> to_iban('8601 11 17947')
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'NO93 8601 11 17947'
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"""
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from __future__ import annotations
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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, 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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number = clean(number, ' .-').strip()
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if number.startswith('0000'):
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number = number[4:] # strip leading 0000 postgiro bank code
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return number
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def _calc_check_digit(number: str) -> str:
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"""Calculate the check digit for the 11-digit number."""
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weights = (6, 7, 8, 9, 4, 5, 6, 7, 8, 9)
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return str(sum(w * int(n) for w, n in zip(weights, number)) % 11)
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def validate(number: str) -> str:
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"""Check if the number provided is a valid bank account number."""
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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) == 7:
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luhn.validate(number)
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elif len(number) == 11:
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if _calc_check_digit(number) != 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: str) -> bool:
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"""Check if the number provided is a valid bank account number."""
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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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def to_iban(number: str) -> str:
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"""Convert the number to an IBAN."""
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from stdnum import iban
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separator = ' ' if ' ' in number else ''
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return separator.join((
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'NO' + iban.calc_check_digits('NO00' + number),
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number))
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def format(number: str) -> str:
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"""Reformat the number to the standard presentation format."""
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number = compact(number).zfill(11)
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return '.'.join([
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number[:4],
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number[4:6],
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number[6:],
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])
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