I don’t know if one night would do the job. I have seen rattlesnakes sit in ice in a cooler for a couple of days and warm up as if nothing had happened.
I don’t know if one night would be python genocide either but remember the python is tropical and the rattlesnake isn’t. Up here, rattlesnakes in their burrows get frozen all the time and still emerge in the late winter or spring. Pythons, as far as I know, aren’t adapted at all to cold conditions.