Moveit: Moveit_commander.roscpp_initialize method throws C++ No registered converter (TypeError)

[rickstaa]

Problem description

When trying to debug a script, which contains the moveit_commander.roscpp_initialize method, using the ptvsd debugger I get the following error:

Exception has occurred: TypeError
No registered converter was able to produce a C++ rvalue of type std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > from this Python object of type unicode
  File "/opt/ros/melodic/lib/python2.7/dist-packages/moveit_commander/roscpp_initializer.py", line 40, in roscpp_initialize
    _moveit_roscpp_initializer.roscpp_init("move_group_commander_wrappers", args2)
  File "/home/ricks/Development/panda_openai_sim_ws/src/panda_reach_training/sandbox/scripts/other/moveit_commander_test.py", line 15, in <module>
    moveit_commander.roscpp_initialize(sys.argv)

Your environment

• ROS Distro: Melodic
• OS Version: e.g. Ubuntu 18.04
• Binary build: Binary (v1.0.2)

Steps to reproduce

1. Open the vscode IDE.
2. Create a moveit_commander_test script containing the following code:

#! /usr/bin/env python
import sys
import copy
import rospy
import moveit_commander
import moveit_msgs.msg
import geometry_msgs.msg
from math import pi
from std_msgs.msg import String
from moveit_commander.conversions import pose_to_list

if __name__ == "__main__":

    rospy.init_node("move_group_python_interface_tutorial", anonymous=True)
    moveit_commander.roscpp_initialize(sys.argv)

1. Debug the script and watch the error appear.

[rickstaa]

Solution

The problem was caused by the way the PTVSD modifies the system argument vector sys.argv. When debugging a script, it puts the python executable as the first argument of the sys.argv. When debugging a ROS python script containing the moveit_commander.roscpp_initialize method you, therefore, have to remove the python executable from the sys.argv.

[drfuzzyness]

For future visitors, one ugly solution is to run code like this whenever you initialize moveit_commander.

cleaned_args = [ a for a in sys.argv if not a.endswith("my_script_name_here.py") ]
moveit_commander.roscpp_initialize(cleaned_args)

[rickstaa]

@drfuzzyness Thanks a lot for your solution. Thats more failproof than my quick and dirty solution in which i just replaced sys.argv with []. Based on your solution, I now use:

import os
cleaned_args = [a for a in sys.argv if not os.path.basename(__file__) in os.path.basename(__file__)]
moveit_commander.roscpp_initialize(cleaned_args)

I am however unsure whether this works in all run cases.

[danem]

What about using rospy.myargv() to get the cleaned arguments?

[rhaschke]

@rickstaa, I cannot reproduce this issue (anymore?).
Is it still a problem with a recent version of vscode?

[rickstaa]

@rhaschke Thanks for the update! I just performed some tests and this problem seems to be solved for vscode version 1.46.0-insiders. As a result, the solutions above are no longer needed.