I copy pasted this to https://colab.research.google.com (google's jupyter notebook implementation) and added some of my own notes.
https://drive.google.com/file/d/1KFFdyYaU1rbM9G6Vx4rMEL9fIXAx4A84/view?usp=sharing

Hope it helps someone get their hands dirty with decision trees! BIG Thanks to random-forests as well!