70 lines
2.4 KiB
Python
70 lines
2.4 KiB
Python
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# ean.py - functions for handling EANs
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#
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# Copyright (C) 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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"""EAN (International Article Number).
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Module for handling EAN (International Article Number) codes. This
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module handles numbers EAN-13, EAN-8 and UPC (12-digit) format.
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>>> validate('73513537')
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'73513537'
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>>> validate('978-0-471-11709-4') # EAN-13 format
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'9780471117094'
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"""
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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 EAN to the minimal representation. This strips the number
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of any valid separators and removes surrounding whitespace."""
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return clean(number, ' -').strip()
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def calc_check_digit(number):
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"""Calculate the EAN check digit for 13-digit numbers. The number passed
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should not have the check bit included."""
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return str((10 - sum((3 - 2 * (i % 2)) * int(n)
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for i, n in enumerate(reversed(number)))) % 10)
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def validate(number):
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"""Checks to see if the number provided is a valid EAN-13. This checks
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the length and the check bit but does not check whether a known GS1
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Prefix and company identifier are referenced."""
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number = compact(number)
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if not number.isdigit():
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raise InvalidFormat()
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if len(number) not in (13, 12, 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 EAN-13. This checks
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the length and the check bit but does not check whether a known GS1
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Prefix and company identifier are referenced."""
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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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