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# pvm.py - functions for handling Lithuanian 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
"""PVM (Pridėtinės vertės mokestis mokėtojo kodas, Lithuanian VAT number).
The PVM is used for VAT purposes in Lithuania. It is 9 digits (for legal
entities) or 12 digits long (for temporarily registered taxpayers). This
module does not check the format of Lithuanian personal codes (Asmens
kodas).
>>> validate('119511515') # organisation
'119511515'
>>> validate('LT 100001919017') # temporarily registered
'100001919017'
>>> validate('100001919018') # invalid check digit
Traceback (most recent call last):
...
InvalidChecksum: ...
>>> validate('100004801610') # second step in check digit calculation
'100004801610'
"""
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, ' -').upper().strip()
if number.startswith('LT'):
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 = sum((1 + i % 9) * int(n) for i, n in enumerate(number)) % 11
if check == 10:
check = sum((1 + (i + 2) % 9) * int(n) for i, n in enumerate(number))
return str(check % 11 % 10)
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) == 9:
# legal entities
if number[7] != '1':
raise InvalidComponent()
elif len(number) == 12:
# temporary tax payers and natural persons
if number[10] != '1':
raise InvalidComponent()
else:
raise InvalidLength()
if calc_check_digit(number[:-1]) != number[-1]:
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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