Annotated Calculator program from Chapter 6

[cortical_iv]

I made a WAY too annotated (both with comments and print statements in the code) version of the calculator in Chapter 6. Reading the chapter was largely useless for me, I had to work through the code, and this is one of the intermediate steps I created along the way to help me understand:
https://gist.github.com/cortical-iv/4c19719bbce455ec3f2d043fa011d638

I hope it helps someone: I wish I had had this a week ago!