You can use a motion actuator for movement.
c = GameLogic.getCurrentController() #Gets the controller
motion = c.getActuator("motion") #Controller connected to a motion actuator with that name
#Now you can access the forces on the motion actuator with these functions:
motion.setDLoc(x,y,z,l) #corresponding to those values on the actuator
#At the end of the script, you will want to APPLY or FIRE the actuator, you do this with this command:
GameLogic.addActiveActuator(motion,1) #The 1 tells it to turn the act on, a 0 means turn it off
#Blender automatically imports GameLogic for you, so you don’t have to import it in the script, but it doesn’t hurt anything if you do