From the command line enter (in some cases you have to preced the
$ pip install isbnlib
$ easy_install isbnlib
$ pip install isbnlib-3.9.1.tar.gz
(first you have to download the file!)
If you use linux systems, you can install using your distribution package
manager (all major distributions have packages
python3-isbnlib), however (usually) are very old and don’t work well anymore!