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# iban.py - functions for handling International Bank Account Numbers (IBANs)
#
# Copyright (C) 2011 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
"""Module for handling IBANs (International Bank Account Numbers)
numbers, used to identify bank accounts across national borders.
>>> is_valid('GR16 0110 1050 0000 1054 7023 795')
True
>>> is_valid('BE31435411161155')
True
>>> compact('GR16 0110 1050 0000 1054 7023 795')
'GR1601101050000010547023795'
>>> format('GR1601101050000010547023795')
'GR16 0110 1050 0000 1054 7023 795'
"""
from stdnum import numdb
from stdnum.iso7064 import mod_97_10
import re
# our open copy of the IBAN database
_ibandb = numdb.get('iban')
def compact(number):
"""Convert the iban number to the minimal representation. This strips the
number of any valid separators and removes surrounding whitespace."""
return number.replace(' ','').replace('-','').strip().upper()
_alphabet = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'
def _convert(number):
"""Prepare the number to it's base10 representation (also moving the
check digits to the end) so it can be checked with the ISO 7064
Mod 97, 10 algorithm."""
# TODO: find out whether this should be in the mod_97_10 module
return ''.join(str(_alphabet.index(x)) for x in number[4:] + number[:4])
# regular expression to check IBAN structure
_struct_re = re.compile('([1-9][0-9]*)!([nac])')
def _matches_structure(number, structure):
"""Check the supplied number against the supplied structure."""
start = 0
for length, code in _struct_re.findall(structure):
length = int(length)
if code == 'n' and not number[start:start + length].isdigit():
return False
elif code == 'a' and not number[start:start + length].isalpha():
return False
elif code == 'c' and not number[start:start + length].isalnum():
return False # should not happen due to checksum check
start += length
# the whole number should be parsed now
return start == len(number)
def is_valid(number):
"""Checks to see if the number provided is a valid IBAN."""
try:
number = compact(number)
# ensure that checksum is valid
if not mod_97_10.is_valid(_convert(number)):
return False
except:
return False
# look up the number
info = _ibandb.info(number)
# check if the number has the correct structure
return _matches_structure(number[4:], info[0][1].get('bban', ''))
def format(number, separator=' '):
"""Reformat the passed number to the space-separated format."""
number = compact(number)
return separator.join(number[i:i+4] for i in range(0,len(number),4))
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