This is an obvious extension of my previous post (3-Layer Neural Network). I have only made changes to Network.py and TestNetwork.py. I have also added a new class called “layer” which contains the definition of a network layer.
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Elements of Reusable Object-Oriented Software

by:
       Erich Gamma
       Richard Helm
       Ralph Johnson
       John Vlissides

forward by:
       Grady Booch

or “My first neural network in python”

This is an implementation of a typical 3-Layer neural network. There are three classes, Neuron, Link and Network. The Neuron class defines the perceptron, the link class defines links between perceptrons and finally the Network class defines the actual network. I could get into the details of the implementation but there are already many resources out there.
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A branch of knowledge concerned with causes ; specifically : a branch of medical science concerned with the causes and origins of diseases (m-w.com)