python

Some excellent Python tutorials.

Lists:
http://effbot.org/zone/python-list.htm
https://www.digitalocean.com/community/tutorials/understanding-lists-in-python-3

An interactive tutorial.
https://www.learnpython.org/en/Lists

Dictionaries:
https://www.saltycrane.com/blog/2007/09/how-to-sort-python-dictionary-by-keys/

List Enumeration/Loops:
http://treyhunner.com/2016/04/how-to-loop-with-indexes-in-python/

Numpy
https://www.machinelearningplus.com/101-numpy-exercises-python/

Matplotlib:
https://www.labri.fr/perso/nrougier/teaching/matplotlib/

Clustering:
https://joernhees.de/blog/2015/08/26/scipy-hierarchical-clustering-and-dendrogram-tutorial/

Date/Timestamping:
https://www.saltycrane.com/blog/2008/06/how-to-get-current-date-and-time-in/