urx is a python library to control a robot from 'Universal robot'. 

It is meaned as an easy to use module for pick and place like programming,
 although it has been used for welding and other application with rather low update rate.

Both the 'secondary port' interface and the real-time/matlab interface of the UR controller are used. 
urx can optionally use the python-math3d https://launchpad.net/pymath3d library to receive and send transformation matrices to the robot
urx is known to work with all release robots from Universal Robot.

urx was primarily developed by Olivier Roulet-Dubonnet for Sintef Raufoss Manufacturing and is published under the GPL license: 
http://www.sintef.no/manufacturing/

Example use:

import urx

rob = urx.robot("192.168.0.100")
rob.set_tcp((0, 0, 0.1, 0, 0, 0))
rob.set_payload(2, (0, 0, 0.1))
rob.movej((1, 2, 3, 4, 5, 6), a, v) 
rob.movel((x, y, z, rx, ry, rz), a, v)
print "Current tool pose is: ",  rob.getl()
rob.movel((0.1, 0, 0, 0, 0, 0), a, v, relative=true)# move relative to current pose
rob.translate((0.1, 0, 0), a, v) #move tool and keep orientation
rob.stopj(a)

robot.movel(x, y, z, rx, ry, rz), wait=False)
while True :
    sleep(0.1) #sleep first since the robot may not have processed the command yet
    if robot.is_program_running():
        break

robot.movel(x, y, z, rx, ry, rz), wait=False)
while.robot.getForce() < 50:
    sleep(0.01)
    if not robot.is_program_running():
        break
robot.stopl()

try:
    robot.movel((0,0,0.1,0,0,0), relative=True)
except RobotError, ex:
    print "Robot could not execute move (emergency stop for example), do something", ex

Development using Transform objects from math3d library:

robot = Robot("192.168.1.1")
robot.set_tcp((0,0,0.23,0,0,0)
robot.csys.orient.rotate_zb(pi/4) #just an example
trans = robot.get_pose() # get current transformation matrix (tool to base)
trans.orient.rotate_yt(pi/2)
robot.set_pose(trans)
trans.pos += math3d.Vector(0,0,0.3)
robot.set_pose(trans)


#or only work with orientation part
o = robot.get_orientation()
o.rotate_yb(pi)
robot.set_orientation(o)