First of all, thanks for the great neural network example.

I've got an error trying to run the 01/03 script (Let's code a Neural Network in plain NumPy):

Traceback (most recent call last):
  File "/mynn/main.py", line 60, in <module>
    params_values = train(np.transpose(X_train), np.transpose(y_train.reshape((y_train.shape[0], 1))), NN_ARCHITECTURE, 10, 0.01)[0]
KeyError: 0

I think there is unnecessary [0] index reference. After removing this everything run smoothly.

By the way I've also removed unnecessary semicolons in the python scripts.