The Python Repl

For better interaction while programming CRAM utilises a Repl interface. To get a similar experience in PyCRAM we use the IPython interactive console. In the following we will describe how to install IPython and how to use it as a PyCRAM Repl

To install IPython in Ubuntu just use the command below.

 apt-get install ipython3 

For convenience it is advised to create a setup file which configures the BulletWorld and defines some helper functions. This setup file could look something like this:

 
import rospy
from pycram.ik import ik
from pycram import bullet_world, bullet_world_reasoning
from pycram.robot_description import InitializedRobotDescription as robot_description

world = bullet_world.BulletWorld()

robot = bullet_world.Object("boxy", "robot", "resources/boxy.urdf", [0, 0, 0], [0, 0, 0, 1])
floor = bullet_world.Object("floor", "environment", "resources/plane.urdf")
milk = bullet_world.Object("milk", "milk"m "resources/milk.obj")
world.robot = robot

tool = robot.get_link_position_and_orientation(robot_description.i.get_tool_frame("left"))
world.add_vis_axis(tool)

def move_milk_to_hand():
    hand_pose = robot.get_link_position(tool)
    milk.set_position(hand_pose)

Now start the IPython shell in the terminal by typing the following command:

ipython3

By default IPython starts in the current directory of the terminal. Next, navigate to the directory where the setup file is located. For this you can use the commands

cd

and

ls

Lastly, execute the setup file by typing

run <name of your setupfile>.py 

Now the BulletWorld window should show up and load all objects specified in the setup file. After everything is loaded you are presented with a prompt where you can now type python code as well as use the objects which are initialized in the executed code.

To use changes made in the Python file while the Repl is running you need to enable the iPython extension autoreload. This can be done by typing the following commands in the iPython console.

%load_ext autoreload

This loads the extension.

%autoreload 2

This command configures autoreload to reload all imported modules before the code is executed.