Snippet of code showing the training function for a Neuron.

train.py

def train(self, previous_layer):
    for synapse in self.synapses:
        # Propagate the error back down the synapse to the neuron in the layer below
        previous_layer.neurons[synapse.input_neuron_index].error += self.error * sigmoid_derivative(self.output) * synapse.weight
        # Adjust the synapse weight
        synapse.weight += synapse.signal * self.error * sigmoid_derivative(self.output)
    return previous_layer