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# vat.py - functions for handling Slovak 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
"""IČ DPH (IČ pre daň z pridanej hodnoty, Slovak VAT number).
The IČ DPH (Identifikačné číslo pre daň z pridanej hodnoty) is a 10-digit
number used for VAT purposes. It has a straightforward checksum.
>>> validate('SK 202 274 96 19')
'2022749619'
>>> validate('SK 202 274 96 18') # invalid check digits
Traceback (most recent call last):
...
InvalidChecksum: ...
"""
from stdnum.exceptions import *
from stdnum.sk import rc
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, ' -').upper().strip()
if number.startswith('SK'):
number = number[2:]
return number
def checksum(number):
"""Calculate the checksum."""
return int(number) % 11
def validate(number):
"""Check if the number is a valid VAT number. This checks the length,
formatting and check digit."""
number = compact(number)
if not isdigits(number):
raise InvalidFormat()
if len(number) != 10:
raise InvalidLength()
# it is unclear whether the RČ can be used as a valid VAT number
if rc.is_valid(number):
return number
if number[0] == '0' or int(number[2]) not in (2, 3, 4, 7, 8, 9):
raise InvalidFormat()
if checksum(number) != 0:
raise InvalidChecksum()
return number
def is_valid(number):
"""Check if the number is a valid VAT number."""
try:
return bool(validate(number))
except ValidationError:
return False
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