b58_isbn.py

from baseconv import base58
from isbnlib import is_isbn13, check_digit13


def compress_isbn(isbn):
    # compresses a valid checkdigit ISBN13
    isbn = isbn.replace('-', '')
    assert is_isbn13(isbn)
    prefix = isbn[:3]
    body = isbn[3:-1]
    n = int(body)
    if prefix == '979':
        n += 10**9
    return base58.encode(n)


def decompress_isbn(s):
    n = int(base58.decode(s))
    n += 978 * 10**9
    n = str(n)
    c = check_digit13(n)
    return f'{n}{c}'

compress.py

#!/usr/bin/env python3

from baseconv import base58
from isbnlib import is_isbn13, check_digit13
import sys

def compress_isbn(isbn):
    # compresses a valid checkdigit ISBN13
    isbn = isbn.replace('-', '')
    assert is_isbn13(isbn)
    prefix = isbn[:3]
    body = isbn[3:-1]
    n = int(body)
    if prefix == '979':
        n += 10**9
    return base58.encode(n)


def decompress_isbn(s):
    n = int(base58.decode(s))
    n += 978 * 10**9
    n = str(n)
    c = check_digit13(n)
    return f'{n}{c}'

if __name__ == '__main__':
    with open(sys.argv[1], 'r') as f:
        for line in f:
            print(compress_isbn(line.strip()))