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# kontonr.py - functions for handling Norwegian bank account numbers
# coding: utf-8
#
# Copyright (C) 2018 Arthur de Jong
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301 USA
"""Konto nr. (Norwegian bank account number)
Konto nr. is the country-specific part in Norwegian IBAN codes. The number
consists of 11 digits, the first 4 are the bank identifier and the last is a
check digit. This module does not check if the bank identifier exists.
More information:
* https://www.ecbs.org/iban/norway-bank-account-number.html
>>> validate('8601 11 17947')
'86011117947'
>>> validate('0000.4090403') # postgiro bank code
'4090403'
>>> validate('8601 11 17949') # invalid check digits
Traceback (most recent call last):
...
InvalidChecksum: ...
>>> format('86011117947')
'8601.11.17947'
>>> to_iban('8601 11 17947')
'NO93 8601 11 17947'
"""
from stdnum import luhn
from stdnum.exceptions import *
from stdnum.util import clean, isdigits
def compact(number):
"""Convert the number to the minimal representation. This strips the
number of any valid separators and removes surrounding whitespace."""
number = clean(number, ' .-').strip()
if number.startswith('0000'):
number = number[4:] # strip leading 0000 postgiro bank code
return number
def _calc_check_digit(number):
"""Calculate the check digit for the 11-digit number."""
weights = (6, 7, 8, 9, 4, 5, 6, 7, 8, 9)
return str(sum(w * int(n) for w, n in zip(weights, number)) % 11)
def validate(number):
"""Check if the number provided is a valid bank account number."""
number = compact(number)
if not isdigits(number):
raise InvalidFormat()
if len(number) == 7:
luhn.validate(number)
elif len(number) == 11:
if _calc_check_digit(number) != number[-1]:
raise InvalidChecksum()
else:
raise InvalidLength()
return number
def is_valid(number):
"""Check if the number provided is a valid bank account number."""
try:
return bool(validate(number))
except ValidationError:
return False
def to_iban(number):
"""Convert the number to an IBAN."""
from stdnum import iban
separator = ' ' if ' ' in number else ''
return separator.join((
'NO' + iban.calc_check_digits('NO00' + number),
number))
def format(number):
"""Reformat the number to the standard presentation format."""
number = compact(number).zfill(11)
return '.'.join([
number[:4],
number[4:6],
number[6:],
])
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