Using the code presented by Steve Cousins on his article : "ROS on the
PR2", IEEE RAM Sept. 2010 :
import rospy
from actionlib import SimpleActionClient
from pr2_controllers_msgs.msg import PointHeadAction, PointHeadGoal
from geometry_msgs.msg import Point
client.send_goal(g)
client.wait_for_result()
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Putting at the begin of the program above :