Can't import rospy because of ModuleNotFoundError: No module named 'rospkg'

Question

I started working with ROS and I am having some troubles with the environment and imports (i know that's dumb)... Basically I can't import the rospy library in my python file, which should be straightforward.

#!/usr/bin/env python3

import rospy
from rosplan_knowledge_msgs.msg import KnowledgeItem
from rosplan_knowledge_msgs.srv import KnowledgeUpdateService, KnowledgeUpdateServiceRequest

class PlatformStatusHandler : 
    def __init__(self, robot_id, energy_level, health_status, current_profile) -> None:
        self.robot_id = robot_id
        self.energy_level = energy_level
        self.health_status = health_status 

        self.current_profile = current_profile

    
    def test_rosplan_db(self, ins_type, ins_name, update_type) : 
            
            rospy.wait_for_service('/rosplan_knowledge_base/update')
            knowledge_update_proxy = rospy.ServiceProxy('/rosplan_knowledge_base/update', KnowledgeUpdateService)

            req = KnowledgeUpdateServiceRequest()
            req.knowledge.knowledge_type = KnowledgeItem.INSTANCE
            req.knowledge.instance_type = ins_type
            req.knowledge.instance_name = ins_name
            req.update_type = update_type
            success = success and knowledge_update_proxy(req).success

(new_env) benjies@benjies-Precision-3571:~/Workspace_c/SoaR_pipeline$ python3 PlatformStatusHandler.py 
Traceback (most recent call last):
  File "PlatformStatusHandler.py", line 3, in <module>
    import rospy
  File "/opt/ros/noetic/lib/python3/dist-packages/rospy/__init__.py", line 49, in <module>
    from .client import spin, myargv, init_node, \
  File "/opt/ros/noetic/lib/python3/dist-packages/rospy/client.py", line 52, in <module>
    import roslib
  File "/opt/ros/noetic/lib/python3/dist-packages/roslib/__init__.py", line 50, in <module>
    from roslib.launcher import load_manifest  # noqa: F401
  File "/opt/ros/noetic/lib/python3/dist-packages/roslib/launcher.py", line 42, in <module>
    import rospkg
ModuleNotFoundError: No module named 'rospkg'

That is the code I am working on but I can't go beyond the first line. Here is the content of my ROS_PACKAGE_PATH if that's of any help, maybe I am messing things up on that level.

echo $ROS_PACKAGE_PATH
/home/benjies/ROSPlan_workspace/src/ROSPlan/rosplan:/home/benjies/ROSPlan_workspace/src/ROSPlan/rosplan_action_interface:/home/benjies/ROSPlan_workspace/src/ROSPlan/rosplan_dispatch_msgs:/home/benjies/ROSPlan_workspace/src/ROSPlan/rosplan_knowledge_msgs:/home/benjies/ROSPlan_workspace/src/ROSPlan/rosplan_dependencies:/home/benjies/ROSPlan_workspace/src/ROSPlan/rosplan_knowledge_base:/home/benjies/ROSPlan_workspace/src/ROSPlan/rosplan_planning_system:/home/benjies/ROSPlan_workspace/src/ROSPlan/rosplan_rqt:/home/benjies/ROSPlan_workspace/src/ROSPlan/rosplan_sensing_interface:/home/benjies/catkin_ws/src:/opt/ros/noetic/share

Answer 1

It's possible you haven't sourced your ROS install directory in the terminal window you're using. ROS doesn't do this automatically, to avoid problems if people have multiple distros installed - try something along the lines of:

# Source our ROS2 installation
source /opt/ros/humble/setup.bash
source ~/dev/ros2/install/setup.bash

Either each time you want to run ros code in a terminal, or you could add these lines to your .bashrc file if you don't mind them always being sourced