I’m using up-to-date Ubuntu 18.04.
Yesterday I didn’t put my work computer to suspend and didn’t run into any CUDA problem all day (should have suspended at end of day to see its effect but got caught up in something else).  Rebooted my home computer and also didn’t run into any CUDA problem.  Suspended it overnight and this morning, CUDA was no longer accessibly via Python.  Maybe worth noting that the GPU was still being used by Xorg and programs running on Xorg (my home computer uses GPU for video, work computer does not).
Will continue to test today.  If this is a suspend issue, anywhere in particular I should report it to?
Peter