Usually? Yes, but it is immaterial to my safety, and more just because my girlfriend is often around, and not because I asked someone in particular to be around while I handle one of the larger snakes in my collection.
I have zero safety issues with my 6+ foot carpet python, but then again he's still under 10lbs, so he really isn't that big of a snake.
There is a threshold where I don't feel comfortable handling a snake by myself, and 100lbs is certainly past that threshold, but I don't know what my threshold exactly is.