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# ddv.py - functions for handling Slovenian VAT numbers
# coding: utf-8
#
# Copyright (C) 2012, 2013 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
"""ID za DDV (Davčna številka, Slovenian VAT number).
The DDV number (Davčna številka) is used for VAT (DDV, Davek na dodano
vrednost) purposes and consist of 8 digits of which the last is a check
digit.
>>> validate('SI 5022 3054')
'50223054'
>>> validate('SI 50223055') # invalid check digits
Traceback (most recent call last):
...
InvalidChecksum: ...
"""
from stdnum.exceptions import *
from stdnum.util import clean
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, ' -').upper().strip()
if number.startswith('SI'):
number = number[2:]
return number
def calc_check_digit(number):
"""Calculate the check digit. The number passed should not have the
check digit included."""
check = (11 - sum((8 - i) * int(n) for i, n in enumerate(number)) % 11)
# this results in a two-digit check digit for 11 which should be wrong
return '0' if check == 10 else str(check)
def validate(number):
"""Checks to see if the number provided is a valid VAT number. This
checks the length, formatting and check digit."""
number = compact(number)
if not number.isdigit() or number.startswith('0'):
raise InvalidFormat()
if len(number) != 8:
raise InvalidLength()
if calc_check_digit(number[:-1]) != number[-1]:
raise InvalidChecksum()
return number
def is_valid(number):
"""Checks to see if the number provided is a valid VAT number. This
checks the length, formatting and check digit."""
try:
return bool(validate(number))
except ValidationError:
return False
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