fodselsnummer.py

"""Functions for validation and generation of Norwegian fodselsnumbers"""

import re
from datetime import date, datetime, timedelta as td

FNR_REGEX = re.compile(r'\d{11}')

class FodselsnummerException(Exception):
    pass
class InvalidControlDigitException(FodselsnummerException):
    pass


def check_fnr(fnr, d_numbers=True):
    """
    Check if a number is a valid fodselsnumber.

    Only checks the control digits, does not check if the
    individual numbers are used in the relevant year

    Args:
        fnr: A string containing the fodselsnummer to check
        d_numbers: True (the default) if d-numbers should be accepted
    Returns:
        True if it is a valid fodselsnummer, False otherwise.
    """
    if not FNR_REGEX.match(fnr):
        return False

    try:
        datetime.strptime(fnr[0:6], '%d%m%y')
    except ValueError:
        if d_numbers:
            dnrdatestring = str(int(fnr[0])-4) + fnr[1:6]
            try:
                datetime.strptime(dnrdatestring, '%d%m%y')
            except ValueError:
                return False
        else:
            return False

    try:
        generatedfnr = _generate_control_digits(fnr[0:9])
    except InvalidControlDigitException:
        return False

    return bool(fnr == generatedfnr)

def generate_fnr_for_year(year, d_numbers):
    """
    Generates all the possible fodselsnumbers for a year.

    Args:
        year: The year to generate fodselsnummers for (integer)
        d_numbers: True if you want d-numbers as well, False otherwise.
    Returns:
        A list with all the possible fodselsnummers for that year.
    """
    allfnrs = []
    startdate = date(year, 1, 1)
    enddate = date(year, 12, 31)
    delta = enddate - startdate
    for i in range(delta.days + 1):
        allfnrs += generate_fnr_for_day(startdate + td(days=i), d_numbers)
    return allfnrs

def generate_fnr_for_day(day, d_numbers):
    """
    Generates all the possible fodselsnumbers for a day.

    Args:
        day: The day to generate fodslesnummers for (datetime)
        d_numbers: True if you want d-numbers as well, False otherwise.
    Returns:
        A list with all the possible fodselsnummers for that day.
    """
    thisdaysfnr = []
    stupid1900s = False
    datestring = day.strftime('%d%m%y')
    if d_numbers:
        dnrdatestring = str(int(datestring[0])+4) + datestring[1:]
    # ref:
    # http://www.kith.no/upload/5588/KITH1001-2010_Identifikatorer-for-personer_v1.pdf
    # Does not account for the 1800s, since this is for living persons
    # (this means that the 1800s list will be a little longer than necessary)
    if 1900 <= day.year <= 1999:
        individualmin = 000
        individualmax = 499
        if 1940 <= day.year <= 1999:
            stupid1900s = True
    else:
        individualmin = 500
        individualmax = 999
    for x in range(individualmin, individualmax+1):
        individualnr = str(x).zfill(3)
        try:
            thisdaysfnr.append(_generate_control_digits(datestring + individualnr))
        except InvalidControlDigitException:
            pass
        if d_numbers:
            try:
                thisdaysfnr.append(_generate_control_digits(dnrdatestring + individualnr))
            except InvalidControlDigitException:
                pass
    # Bonus round because of the stupid 1900s
    if stupid1900s:
        for x in range(900, 1000):
            individual_nr = str(x).zfill(3)
            try:
                thisdaysfnr.append(_generate_control_digits(datestring + individualnr))
            except InvalidControlDigitException:
                pass
            if d_numbers:
                try:
                    thisdaysfnr.append(_generate_control_digits(dnrdatestring + individualnr))
                except InvalidControlDigitException:
                    pass
    return thisdaysfnr

def _generate_control_digits(numbersofar):
    """Generates the magic control digits in a fodselsnumber"""
    staticnumbers1 = [3, 7, 6, 1, 8, 9, 4, 5, 2, 1]
    staticnumbers2 = [5, 4, 3, 2, 7, 6, 5, 4, 3, 2, 1]
    sum1 = 0
    for x in range(0, 9):
        sum1 += int(numbersofar[x]) * staticnumbers1[x]
    rest = sum1 % 11
    if rest == 0:
        control1 = 0
    else:
        if 11-rest != 10:
            control1 = 11-rest
        else:
            raise InvalidControlDigitException
    numbersofar += str(control1)
    sum2 = 0
    for x in range(0, 10):
        sum2 += int(numbersofar[x]) * staticnumbers2[x]
    rest = sum2 % 11
    if rest == 0:
        control2 = 0
    else:
        if 11-rest != 10:
            control2 = 11-rest
        else:
            raise InvalidControlDigitException
    numbersofar += str(control2)
    return numbersofar