I don't know about affection, but I know mine go through "moods". Sometimes they're good about being picked up and handled, sometimes the flinch irritably when I go to touch them, sometimes they might even hiss at me. I might get certain reactions more from certain snakes, but Ive gotten lots of varied reactions from individuals. Does the presence of moods mean anything about their emotional state? Maybe not, but at the very least it shows me that they are capable of interacting with stressors and other factors and reacting to them, which could mean more than we think it does.