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hornc/validISNI.py

Last active November 20, 2022 21:21
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Validate and ISNI
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validISNI.py
"""
[copied from https://github.com/internetarchive/openlibrary/pull/6841#issuecomment-1207507062]
I'm recording this here because there is very little information currently about ISNI check digits online.
ISNI uses a checkdigit {0-9, X} calculation system which is called something like "MOD 11-2" and is
defined in the standard [ISO 7064](https://en.wikipedia.org/wiki/ISO/IEC_7064), but you have to pay to read it....
The same "MOD 11-2" system is used by the
Chinese [Resident Identity Card](https://en.wikipedia.org/wiki/Resident_Identity_Card),
which has its own specs and more publicly available code examples.
"""
def validISNI(isni):
isni = isni.upper().replace('X', 'A')
return sum([int(c, 16) * 2**(15-i) for i, c in enumerate(isni)]) % 11 == 1
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