87 lines
2.7 KiB
Python
87 lines
2.7 KiB
Python
# tfn.py - functions for handling Australian Tax File Numbers (TFNs)
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#
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# Copyright (C) 2016 Vincent Bastos
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# Copyright (C) 2016 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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"""TFN (Australian Tax File Number).
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The Tax File Number (TFN) is issued by the Australian Taxation Office (ATO)
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to taxpaying individuals and organisations. A business has both a TFN and an
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Australian Business Number (ABN).
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The number consists of 8 (older numbers) or 9 digits and includes a check
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digit but otherwise without structure.
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More information:
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* https://en.wikipedia.org/wiki/Tax_file_number
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* https://www.ato.gov.au/Individuals/Tax-file-number/
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>>> validate('123 456 782')
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'123456782'
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>>> validate('999 999 999')
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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>>> format('123456782')
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'123 456 782'
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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, ' ').strip()
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def checksum(number: str) -> int:
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"""Calculate the checksum."""
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weights = (1, 4, 3, 7, 5, 8, 6, 9, 10)
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return sum(w * int(n) for w, n in zip(weights, number)) % 11
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def validate(number: str) -> str:
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"""Check if the number is a valid TFN. This checks the length, formatting
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and check digit."""
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number = compact(number)
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if not isdigits(number):
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raise InvalidFormat()
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if len(number) not in (8, 9):
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raise InvalidLength()
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if checksum(number) != 0:
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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 TFN."""
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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[0:3], number[3:6], number[6:]))
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