96 lines
3.2 KiB
Python
96 lines
3.2 KiB
Python
# idnr.py - functions for handling German tax id
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# coding: utf-8
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#
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# Copyright (C) 2017 Holvi Payment Services Oy
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# Copyright (C) 2017 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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"""IdNr (Steuerliche Identifikationsnummer, German personal tax number).
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The IdNr (or Steuer-IdNr) is a personal identification number that is
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assigned to individuals in Germany for tax purposes and is meant to replace
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the Steuernummer. The number consists of 11 digits and does not embed any
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personal information.
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More information:
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* https://de.wikipedia.org/wiki/Steuerliche_Identifikationsnummer
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* http://www.identifikationsmerkmal.de/
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>>> validate('36 574 261 809')
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'36574261809'
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>>> validate('36574261890')
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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>>> validate('36554266806') # more digits repeated
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Traceback (most recent call last):
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...
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InvalidFormat: ...
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>>> format('36574261809')
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'36 574 261 809'
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"""
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from __future__ import annotations
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from collections import defaultdict
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from stdnum.exceptions import *
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from stdnum.iso7064 import mod_11_10
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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, ' -./,').strip()
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def validate(number: str) -> str:
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"""Check if the number provided is a valid tax identification number.
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This checks the length, formatting and check digit."""
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number = compact(number)
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if len(number) != 11:
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raise InvalidLength()
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if not isdigits(number):
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raise InvalidFormat()
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if number.startswith('0'):
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raise InvalidFormat()
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# In the first 10 digits exactly one digit must be repeated two or
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# three times and other digits can appear only once.
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counter: dict[str, int] = defaultdict(int)
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for n in number[:10]:
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counter[n] += 1
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counts = [c for c in counter.values() if c > 1]
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if len(counts) != 1 or counts[0] not in (2, 3):
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raise InvalidFormat()
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return mod_11_10.validate(number)
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def is_valid(number: str) -> bool:
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"""Check if the number provided is a valid tax identification number.
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This checks 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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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[:2], number[2:5], number[5:8], number[8:]))
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