Your cats are safe. A 3' long, 1" wide snake is looking for mice and very small rats. We are talking about the slender bodied rat snake, right?

A 6' long, 3" wide snake could be a danger to a small cat but the snake would probably run away from the cat. If that snake is heavy bodied enough to weigh 20 pounds or so, then that is a different story.

Thanks Greg. Yes, the one in the house was a slender snake.

A 3" wide snake couldn't get under the doors.

I guess the wife's cats will be OK.

Even though Rat Snakes do dine on small mammals I have not heard of one attacking a cat which would be about four times as large as a chipmunk, or more. Also, contrary to some myths, these snakes do not wrap themselves around prey and squeeze as a constrictor would. While they do wrap themselves around tree branches that is to hold on and is not a means of obtaining prey.

Here is a link that might be useful: About Rat Snakes

Kimmsr, Rat snakes ARE constrictors and that is exactly how they subdue their prey. Your attached link clearly says that.

Don't forget the other food item of rat snakes...probably mentioned in the link someone provided. Rat snakes also eat other snakes. Encourage your rat snake to hang out. You may get startled when you see him now and then but he will eat copperheads and other small snakes.

You betchum rat snakes are constrictors.

I'm not sure that encouraging snakes to hang out in the basement is a good idea. I'd be carefully evicting him to the garden and making every effort to seal all of the possible entries for small snakes, mice, and other critters.