Just what the title says!

import maya.cmds as cmds
 swatchState= cmds.renderThumbnailUpdate(q=True)
 if swatchState == 0:
     cmds.renderThumbnailUpdate (1)
     print("\nSwatches turned ON")
 else:
     cmds.renderThumbnailUpdate (0)
     print("\nSwatches turned OFF")