Currently there are 19 native Standard Prime lenses for Pentax KP and 14 of these lenses are autofocus (AF) type.
KP also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on KP.
Since Pentax KP has environmental sealings (Weather Sealing), you may like to couple your camera with one of these 2 Standard Prime lenses with Weather Sealings.