Validate and ISNI

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