124 lines
4.2 KiB
Python
124 lines
4.2 KiB
Python
# cpr.py - functions for handling Danish CPR numbers
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# coding: utf-8
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#
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# Copyright (C) 2012-2019 Arthur de Jong
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# Copyright (C) 2020 Leon Sandøy
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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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"""CPR (personnummer, the Danish citizen number).
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The CPR is the national number to identify Danish citizens and is stored in
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the Det Centrale Personregister (Civil Registration System). The number
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consists of 10 digits in the format DDMMYY-SSSS where the first part
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represents the birth date and the second a sequence number. The first digit
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of the sequence number indicates the century.
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The numbers used to validate using a checksum but since the sequence numbers
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ran out this was abandoned in 2007. It is also not possible to use the
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checksum only for numbers that have a birth date before that because the
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numbers are also assigned to immigrants.
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More information:
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* https://en.wikipedia.org/wiki/Personal_identification_number_(Denmark)
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* https://da.wikipedia.org/wiki/CPR-nummer
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* https://cpr.dk/
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>>> validate('211062-5629')
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'2110625629'
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>>> checksum('2110625629')
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0
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>>> validate('511062-5629') # invalid date
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Traceback (most recent call last):
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...
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InvalidComponent: ...
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>>> validate('2110525629')
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Traceback (most recent call last):
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...
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InvalidComponent: The birth date information is valid, but this person has not been born yet.
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>>> get_birth_date('2110620629')
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datetime.date(1962, 10, 21)
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>>> format('2110625629')
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'211062-5629'
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"""
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from __future__ import annotations
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import datetime
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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. Note that the checksum isn't actually used
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any more. Valid numbers used to have a checksum of 0."""
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weights = (4, 3, 2, 7, 6, 5, 4, 3, 2, 1)
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return sum(w * int(n) for w, n in zip(weights, number)) % 11
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def get_birth_date(number: str) -> datetime.date:
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"""Split the date parts from the number and return the birth date."""
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number = compact(number)
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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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if number[6] in '5678' and year >= 58:
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year += 1800
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elif number[6] in '0123' or (number[6] in '49' and year >= 37):
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year += 1900
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else:
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year += 2000
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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('The number does not contain valid birth date information.')
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def validate(number: str) -> str:
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"""Check if the number provided is a valid CPR number. This checks the
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length, formatting, embedded date 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) != 10:
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raise InvalidLength()
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if get_birth_date(number) > datetime.date.today():
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raise InvalidComponent(
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'The birth date information is valid, but this person has not been born yet.')
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return number
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def is_valid(number: str) -> bool:
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"""Check if the number provided is a valid CPR number. This checks the
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length, formatting, embedded date 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[:6], number[6:]))
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