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ISBN, the International Standard Book Number, will migrate to 13-digits version from current 10-digits version on 2007-01-01. This recipe converts ISBN-10 to ISBN-13 by regenerating the check digit.

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def check_digit_10(isbn):
    assert len(isbn) == 9
    sum = 0
    for i in range(len(isbn)):
        c = int(isbn[i])
        w = i + 1
        sum += w * c
    r = sum % 11
    if r == 10: return 'X'
    else: return str(r)

def check_digit_13(isbn):
    assert len(isbn) == 12
    sum = 0
    for i in range(len(isbn)):
        c = int(isbn[i])
        if i % 2: w = 3
        else: w = 1
        sum += w * c
    r = 10 - (sum % 10)
    if r == 10: return '0'
    else: return str(r)

def convert_10_to_13(isbn):
    assert len(isbn) == 10
    prefix = '978' + isbn[:-1]
    check = check_digit_13(prefix)
    return prefix + check

3 comments

greg p 14 years, 3 months ago  # | flag

Web Based Implementation. I put this recipe into an online calculator:

http://www.utilitymill.com/utility/ISBN_10_to_ISBN_13_Converter

I hope it's useful.

Osvaldo Santana 13 years, 10 months ago  # | flag

Small command line utility. Hi,

I've created a small utility based on this module and I've make some changes on the code too. Take a look at:

http://osantana-code.googlecode.com/svn/trunk/others/isbn.py

Thanks, Osvaldo

Michael Schmidt 12 years, 4 months ago  # | flag

Thanks a lot! Save me a lot of time ...

Michael

Created by Sanghyeon Seo on Fri, 15 Sep 2006 (PSF)
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