I was bitten and constricted by a large yearling (feeding accident).
It hurt, but not enough to do more than make me go 'ow...ow....aw, c'mon, let go'. lol
I slid his tail off of his face, tapped him on the nose a few times, and held still--and he let go.
I don't recommend trying to forcibly remove a snake that is biting and constricting--you are likely to hurt yourself a lot more, and you're likely to break the snake's teeth off, which could remain behind in your skin, since they are so thin. Just remain calm, and let it release you itself.
Even that bite took only 3 days to completely vanish--the wounds are extremely minor, so long as you don't try to pull away or pull the animal off of you.