Hi Ugo,

I can't reproduce your error, but there is a bug in your script:

    motor_node = roslaunch.Node(package = "sr_three_fingers_dynamixel_hand",
                                          node_type="motor.py",
name="dynamixel_motor_"+str(servo))

I assume that you meant str(i):

    motor_node = roslaunch.Node(package = "sr_three_fingers_dynamixel_hand",
                                          node_type="motor.py",
name="dynamixel_motor_"+str(i))

Otherwise you are launching nodes with the same name repeatedly, and
all but one will get killed.

That shouldn't result in the error message your are getting. The error
message you are getting should only happen if you are calling
init_node more than once in your program.

 - Ken


On Fri, Aug 27, 2010 at 10:01 AM, Ugo Cupcic <ugo@shadowrobot.com> wrote:
> Ok, I tried using the roslaunch.scriptapi but encountered a problem:
>
> in my "parent node", I have something like this:
>  self.roslauncher = roslaunch.ROSLaunch()  self.roslauncher.start()  for i
> in range(0,10):     motor_node = roslaunch.Node(package =
> "sr_three_fingers_dynamixel_hand",
> node_type="motor.py", name="dynamixel_motor_"+str(servo))
> self.roslauncher.launch(motor_node)
>
> However if in my spawn child nodes I have:
>  rospy.init_node( 'dynamixel_motor_'+str(motor_id) )
> Then ros complains that the node is already initialized. (raise
> rospy.exceptions.ROSException("rospy.init_node() has already been called
> with different arguments: "+str(_init_node_args)))
>
> If i comment the rospy.init_node then ros doesn't complain and the parent
> node seems to be starting properly, but I don't see my child node in the
> system. rosnode list return the parent node only.
>
> Any idea of what I am doing wrong?
>
> Cheers,
>
> Ugo
>
> On 26/08/10 17:02, Ugo Cupcic wrote:
>
>  Thanks Ken.
>
> On 26/08/10 16:33, Ken Conley wrote:
>
> Multiple ways, yes.
>
> Spawning a ros node is no different from just running a process. So
> the standard Python subprocess module will work.
>
> If you want to get fancier, there are two Python APIs for running
> roslaunch within your own process:
>
>  * roslaunch.scriptapi [1]
>  * roslaunch_caller (unsupported)
>
> [1]:
> http://www.ros.org/doc/api/roslaunch/html/roslaunch.scriptapi.ROSLaunch-class.html
>
> On Thu, Aug 26, 2010 at 1:04 AM, Ugo Cupcic <ugo@shadowrobot.com> wrote:
>
>  Hi all,
>
> Is there a way to spawn multiple nodes directly from a python node?
>
> Cheers,
>
> Ugo
>
> --
> Ugo Cupcic         |  Shadow Robot Company | ugo@shadowrobot.com
> Software Engineer  |    251 Liverpool Road |
> need a Hand?       |    London  N1 1LX     | +44 20 7700 2487
> http://www.shadowrobot.com/hand/              @shadowrobot
>
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>
> --
> Ugo Cupcic         |  Shadow Robot Company | ugo@shadowrobot.com
> Software Engineer  |    251 Liverpool Road |
> need a Hand?       |    London  N1 1LX     | +44 20 7700 2487
> http://www.shadowrobot.com/hand/              @shadowrobot
>
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>