I tried add a new item “bpy.ops.object.mode_set(mode=‘SCULPT’)” in User Preference > Input. But looks like it didn’t work.
You could just set it from the user preferences rather than using python if all you want to do is set a shortcut.
Under 3DView / Object Non-modal you’ll see the default options to change mode. Just amend or duplicate but set the mode dropdown to Sculpt
@Richard Marklew: Thank you as always!