SOMOCLU library
http://peterwittek.github.io/somoclu/
http://peterwittek.com/somoclu-in-python.html
https://somoclu.readthedocs.io/en/stable/reference.html
SOMPY library
https://vahidmoosavi.com/2014/02/18/a-self-organizing-map-som-package-in-python-sompy/
https://github.com/sevamoo/SOMPY
Mini SOM
https://glowingpython.blogspot.jp/2013/09/self-organizing-maps.html
Another implementation
https://github.com/damayanthiHerath/selforganisingmaps
Excellent code walkthrough
http://blog.yhat.com/posts/self-organizing-maps-2.html
Explaination
http://www.ai-junkie.com/ann/som/som1.html
TensorFlow implementation
https://codesachin.wordpress.com/2015/11/28/self-organizing-maps-with-googles-tensorflow/
Code for Kohonen
https://github.com/lmjohns3/kohonen/blob/master/kohonen/kohonen.py