If it's a ball python I have no issues with it around my neck, unless I suspect it'll try to bite my face lol. I just wait until the snake has chilled out a little after being removed, straighten them out a little and put them across the back of my neck. They'll curl around the front with their head and tail on their own, and they're usually happy to chill there.

As for any other constrictor, I wouldn't put anything that gets bigger or stronger than a ball python around my neck, unless I was doing it to hold it like was mentioned with large long snakes, because holding them with your hands and having them lay across the back of your shoulders helps support them a little better.