98 lines
3.2 KiB
Python
98 lines
3.2 KiB
Python
# nit.py - functions for handling Guatemala NIT numbers
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# coding: utf-8
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#
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# Copyright (C) 2019 Leandro Regueiro
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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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"""NIT (Número de Identificación Tributaria, Guatemala tax number).
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The Número de Identificación Tributaria (NIT) is an identifier of legal
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entities for tax purposes in Guatemala.
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The number consists of 2 to 12 characters, where the last one is the check
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digit (a digit or the letter K) and the rest are digits. Leading zeroes are
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usually omitted. Digits and check digit are usually separated with a hyphen.
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More information:
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* https://portal.sat.gob.gt/portal/descarga/6524/factura-electronica-fel/25542/fel-reglas-y-validaciones.pdf (page 58)
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* https://portal.sat.gob.gt/portal/consulta-cui-nit/
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>>> validate('576937-K')
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'576937K'
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>>> validate('7108-0')
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'71080'
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>>> validate('8977112-0')
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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>>> validate('1234567890123')
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Traceback (most recent call last):
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...
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InvalidLength: ...
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>>> format('39525503')
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'3952550-3'
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"""
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from __future__ import annotations
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from stdnum.exceptions import *
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from stdnum.util import clean, isdigits
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def compact(number: str) -> str:
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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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return clean(number, ' -').upper().strip().lstrip('0')
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def calc_check_digit(number: str) -> str:
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"""Calculate the check digit. The number passed should not have the
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check digit included."""
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c = -sum(i * int(n) for i, n in enumerate(reversed(number), 2)) % 11
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return 'K' if c == 10 else str(c)
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def validate(number: str) -> str:
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"""Check if the number is a valid Guatemala NIT number.
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This checks the length, formatting and check digit.
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"""
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number = compact(number)
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if len(number) < 2 or len(number) > 12:
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raise InvalidLength()
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if not isdigits(number[:-1]):
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raise InvalidFormat()
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if number[-1] != 'K' and not isdigits(number[-1]):
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raise InvalidFormat()
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if number[-1] != calc_check_digit(number[:-1]):
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raise InvalidChecksum()
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return number
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def is_valid(number: str) -> bool:
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"""Check if the number is a valid Guatemala NIT number."""
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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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def format(number: str) -> str:
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"""Reformat the number to the standard presentation format."""
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number = compact(number)
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return '-'.join([number[:-1], number[-1]])
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