116 lines
3.9 KiB
Python
116 lines
3.9 KiB
Python
# pvn.py - functions for handling Latvian PVN (VAT) numbers
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# coding: utf-8
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#
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# Copyright (C) 2012, 2013 Arthur de Jong
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301 USA
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"""PVN (Pievienotās vērtības nodokļa, Latvian VAT number).
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The PVN is a 11-digit number that can either be a reference to a legal
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entity (in which case the first digit > 3) or a natural person (in which
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case it should be the same as the personal code (personas kods)). Personal
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codes start with 6 digits to denote the birth date in the form ddmmyy.
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>>> validate('LV 4000 3521 600')
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'40003521600'
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>>> validate('40003521601') # invalid check digit
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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>>> validate('161175-19997') # personal code
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'16117519997'
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>>> validate('161375-19997') # invalid date
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Traceback (most recent call last):
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...
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InvalidComponent: ...
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"""
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import datetime
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from stdnum.exceptions import *
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from stdnum.util import clean
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# validation functions are available on-line but it is not allowed
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# to perform automated queries:
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# http://www6.vid.gov.lv/VID_PDB?aspxerrorpath=/vid_pdb/pvn.asp
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def compact(number):
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"""Convert the number to the minimal representation. This strips the
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number of any valid separators and removes surrounding whitespace."""
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number = clean(number, ' -').upper().strip()
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if number.startswith('LV'):
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number = number[2:]
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return number
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def checksum(number):
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"""Calculate the checksum for legal entities."""
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weights = (9, 1, 4, 8, 3, 10, 2, 5, 7, 6, 1)
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return sum(weights[i] * int(n) for i, n in enumerate(number)) % 11
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def calc_check_digit_pers(number):
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"""Calculate the check digit for personal codes. The number passed
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should not have the check digit included."""
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# note that this algorithm has not been confirmed by an independent source
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weights = (10, 5, 8, 4, 2, 1, 6, 3, 7, 9)
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check = 1 + sum(weights[i] * int(n) for i, n in enumerate(number))
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return str(check % 11 % 10)
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def get_birth_date(number):
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"""Split the date parts from the number and return the birth date."""
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day = int(number[0:2])
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month = int(number[2:4])
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year = int(number[4:6])
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year += 1800 + int(number[6]) * 100
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try:
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return datetime.date(year, month, day)
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except ValueError:
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raise InvalidComponent()
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def validate(number):
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"""Checks to see if the number provided is a valid VAT number. This checks
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the length, formatting and check digit."""
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number = compact(number)
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if not number.isdigit():
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raise InvalidFormat()
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if len(number) != 11:
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raise InvalidLength()
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if number[0] > '3':
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# legal entity
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if checksum(number) != 3:
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raise InvalidChecksum()
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else:
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# natural resident, check if birth date is valid
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birth_date = get_birth_date(number)
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# TODO: check that the birth date is not in the future
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if calc_check_digit_pers(number[:-1]) != number[-1]:
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raise InvalidChecksum()
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return number
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def is_valid(number):
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"""Checks to see if the number provided is a valid VAT number. This checks
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the length, formatting and check digit."""
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try:
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return bool(validate(number))
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except ValidationError:
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return False
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