I am removing some wall sconces so that my walls can be painted.
I will shut off the power while I remove them .... but it'll be a couple of days before they are put back up as the walls are being painted.
Obviously I will need power (and they are not on their own fusebox switch) so how do I ensure that the live wires don't give the painter an electric shock? Do I just wrap some of that electrician's tape on the ends? Is that enough?
Yes, tape is fine.
Just double each wire back onto itself so that the exposed copper bit is completely covered by tape.
If you have plenty of slack available you could snip off the copper and then tape it.