Actually most of the snakes we keep as pets are "constrictors" & they come in all sizes. The alternatives are venomous snakes, which immobilize & kill their prey
with sort of "advanced chemical warfare", or snakes (such as coachwhips & garter snakes) that just simply use their strong jaws to simply over-power & gulp down
their prey. Some technically-venomous snakes are widely-kept pets too...hognose snakes are in that category, they are rear-fanged snakes with mild venom that
isn't considered dangerous to the average (healthy) human. But just because a snake is a constrictor doesn't make it a dangerous pet...rosy boas are constrictors
but pose no concern unless you're a mouse. Most kinds of king snakes get bigger than rosy boas, & many have ferocious appetites, but you're still pretty safe.
But they should all carry a warning...snakes are addicting to keep. LOL