Supporting iPython notebooks for the YouTube Series Neural Networks Demystified. I've included formulas, code, and the text of the movies in the iPython notebooks, in addition to raw code in python scripts.
iPython notebooks can be downloaded and run locally, or viewed using nbviewer: http://nbviewer.ipython.org/.
The iPython/Jupyter notebook is an incredible tool, but can be a little tricky to setup. I recommend the [anaconda] (https://store.continuum.io/cshop/anaconda/) distribution of python. I've written and tested this code with the the anaconda build of python 2 running on OSX. You will likely get a few warnings about contour plotting - if anyone has a fix for this, feel free to submit a pull request.