Neural Network: A Step by Step Backpropagation Example

This great neural network tutorial goes step-by-step through backpropagation in training a neural network. There is also companion python code.

http://mattmazur.com/2015/03/17/a-step-by-step-backpropagation-example/comment-page-1/

see also:

http://denson-data-science.blogspot.com/2015/09/a-neural-network-in-11-lines-of-python.html