Method for checking validity of bulgarian EIK/BULSTAT codes.

eik_checker.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
#       eik_checker.py
#       
#       Copyright 2012 Venelin Stoykov <venelin@magicbg.com>
#       
#       This program is free software; you can redistribute it and/or modify
#       it under the terms of the GNU General Public License as published by
#       the Free Software Foundation; either version 2 of the License, or
#       (at your option) any later version.
#       
#       This program 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 General Public License for more details.
#       
#       You should have received a copy of the GNU General Public License
#       along with this program; if not, write to the Free Software
#       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
#       MA 02110-1301, USA.
 
def eik_checker(eik):
    """
    Check Bulgarian EIK/BULSTAT codes for validity
    full information about algoritm is available here
    http://bulstat.registryagency.bg/About.html
    """

    def get_checksum(weights, digits):
        checksum = sum([weight * digit for weight, digit in zip(weights, digits)])
        return checksum % 11

    def check_eik_base(eik):
        checksum = get_checksum(range(1, 9), eik)
        if checksum == 10:
            checksum = get_checksum(range(3, 11), eik)
        return eik[-1] == checksum % 10

    def check_eik_extra(eik):
        digits = eik[9:13]
        checksum = get_checksum([2, 7, 3, 5], digits)
        if checksum == 10:
            checksum = get_checksum([4, 9, 5, 7], digits)
        return digits[-1] == checksum % 10

    try:
        eik = map(int, eik)
    except ValueError:
        return False

    if not (len(eik) in [9, 13] and check_eik_base(eik)):
        return False

    if len(eik) == 13 and not check_eik_extra(eik):
        return False