Tutorial primitives

Technology
1

There is something I don’t understand with the primitives, for example :

from pypot.primitive import Primitive
class DancePrimitive(Primitive):
    def run(self, amp=30, freq=0.5):
        # self.elapsed_time gives you the time (in s) since the primitive has been running
        while self.elapsed_time < 1:
            x = amp * numpy.sin(2 * numpy.pi * freq * self.elapsed_time)
           
            self.robot.head_z.goal_position = x
            self.robot.head_y.goal_position = -x

            time.sleep(0.05)

My question is, how is it possible to change amp when starting the primitive.

dance = DancePrimitive()
dance.start(amp=60)

The code above doesn’t work because the start method doesn’t accept any argument… I can overwrite the init method with an amp argument but in this case, I don’t need to define amp in the run method… So if someone can help the beginner I am with primitive I will be very grateful.

2

The error is because the start function does indeed not accept an argument. What the start function does is it starts a thread and the thread will use the run function
Start function of the primitive.py file:

def start(self):
        if not self.robot._primitive_manager.running:
            raise RuntimeError('Cannot run a primitive when the sync is stopped!')

        StoppableThread.start(self)
        self.wait_to_start()

        logger.info("Primitive %s started.", self)

I don’t know how you are supposed to change the amplitude with this code.
What you should do (I think) is to add an amplitude field in the DancePrimitive object:

from pypot.primitive import Primitive
class DancePrimitive(Primitive):
    def __init__(self, amp=30, freq=0.5):
        Primitive.__init__(self)
        self.amp = amp
        self.freq=freq

def run(self):
    # self.elapsed_time gives you the time (in s) since the primitive has been running
    while self.elapsed_time < 1:
        x = self.amp * numpy.sin(2 * numpy.pi * self.freq * self.elapsed_time)
       
        self.robot.head_z.goal_position = x
        self.robot.head_y.goal_position = -x

        time.sleep(0.05)

And then create your dance object:

dance = DancePrimitive(amp=60)
dance.start()

Warning, I didn’t test the code

3

Hi,
@Pierre should answer your better, but as far as I know (and looking Primitive code) it is an outdated feature.
I think that the good way is to override the _init_ method (don’t forget to call the super constructor).
Feel free to make pull requests for old or unclear documentation.

EDIT: I didn’t refresh the page so I didn’t see Manon post. She just forget the super constructor:

def __init__(self, robot, amp=30, freq=0.5):
        self.robot = robot
        self.amp = amp
        self.freq = freq
        pypot.primitive.Primitive.__init__(self, robot)
4

Arg, it was there, but wrong (I missed the robot argument).

And yes, the documentation should be updated.

5

Thanks @Manon and @Theo

So if I have a walking primitive, the call should look like :

walk  = walking_primitive(robot,speed=slow)
walk.start()

and to change the speed, I can re-instanciate the object walking_primitive :

walk = walking_primitive(robot,speed=fast)
walk.start()

or I can just change attribut of the primitive :

walk.speed=fast
walk.start()
1 Like
6

Both methods should work, but the second one is better. Make sure the dance is finished before re starting it.

7

Yes indeed, this was an old feature of the primitive which is not supported anymore. Mostly because it wasn’t really clear how to use it.

I have raised an issue to update the doc. This will be for the next pizza doc session :smile:

Do not hesitate to directly raise issue if you see something outdated!