Is there a simple guide to understanding the str/unicode changes from python 2 to 3? I've made mistakes with strings that ruined every single piece of code I'v

Is there a simple guide to understanding the str/unicode changes from python 2 to 3? I've made mistakes with strings that ruined every single piece of code I've upgraded from 2 to 3 unless I just littered the code with defensive six() calls ... and even then some things still broke.