94 lines
2.9 KiB
Python
94 lines
2.9 KiB
Python
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# issn.py - functions for handling ISSNs
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#
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# Copyright (C) 2010, 2011, 2012, 2013 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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"""ISSN (International Standard Serial Number).
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The ISSN (International Standard Serial Number) is the standard code to
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identify periodical publications. It has a checksum similar to ISBN-10.
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>>> validate('0024-9319')
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'00249319'
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>>> validate('0032147X')
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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>>> validate('003214712')
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Traceback (most recent call last):
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...
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InvalidLength: ...
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>>> compact('0032-1478')
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'00321478'
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>>> format('00249319')
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'0024-9319'
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>>> to_ean('0264-3596')
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'9770264359008'
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"""
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from stdnum import ean
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from stdnum.exceptions import *
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from stdnum.util import clean
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def compact(number):
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"""Convert the ISSN to the minimal representation. This strips the number
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of any valid ISSN separators and removes surrounding whitespace."""
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return clean(number, ' -').strip().upper()
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def calc_check_digit(number):
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"""Calculate the ISSN check digit for 10-digit numbers. The number passed
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should not have the check bit included."""
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check = (11 - sum((8 - i) * int(n)
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for i, n in enumerate(number))) % 11
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return 'X' if check == 10 else str(check)
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def validate(number):
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"""Checks to see if the number provided is a valid ISSN. This checks
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the length and whether the check digit is correct."""
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number = compact(number)
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if not number[:-1].isdigit():
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raise InvalidFormat()
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if len(number) != 8:
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raise InvalidLength()
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if calc_check_digit(number[:-1]) != number[-1]:
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raise InvalidChecksum()
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return number
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def is_valid(number):
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"""Checks to see if the number provided is a valid ISSN. This checks
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the length and whether the check digit is correct."""
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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):
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"""Reformat the passed number to the standard format."""
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number = compact(number)
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return number[:4] + '-' + number[4:]
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def to_ean(number, issue_code='00'):
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"""Convert the number to EAN-13 format."""
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number = '977' + validate(number)[:-1] + issue_code
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return number + ean.calc_check_digit(number)
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