Lots of controversy over this topic, MMum. Quick, go grab your flame-retardant blankey and hide!!
Kidding - lots of people house snakes together with success, and lots have tried and it has resulted in the death of either one or both snakes.
Many people will say why would you risk it for the sake of an extra enclosure? Others will point out that they have housed snakes, even of different species, together for long periods , feed them separately, and have no problems, and that the snakes even stress and refuse food when they're separated.
At the end of the day it's up to you if you want to take the risk.
Most people would agree at least that housing snakes of different sizes together wouldn't be a good idea. Good luck!