ModuleNotFoundError: No module named 'rospkg'

Question

I am new to ROS,

I have a problem when I import rospy into my script file example.py and run it: It says:

Traceback (most recent call last):
  File "/home/nagarjunv/hk_ws/src/rvo/src/example.py", line 4, in <module>
    import rospy
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/__init__.py", line 49, in <module>
    from .client import spin, myargv, init_node, \
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/client.py", line 52, in <module>
    import roslib
  File "/opt/ros/melodic/lib/python2.7/dist-packages/roslib/__init__.py", line 50, in <module>
    from roslib.launcher import load_manifest  # noqa: F401
  File "/opt/ros/melodic/lib/python2.7/dist-packages/roslib/launcher.py", line 42, in <module>
    import rospkg
ModuleNotFoundError: No module named 'rospkg'

I am importing the following into my script file:The line 4 is rospy

#!/usr/bin/env python3

import sys
import rospy

THis is my CmakeLists:

cmake_minimum_required(VERSION 3.0.2)
project(rvo)

find_package(catkin REQUIRED COMPONENTS
  rospy
  std_msgs
  message_generation
)

 generate_messages(
   DEPENDENCIES
   std_msgs
 )

catkin_package(
#  INCLUDE_DIRS include
#  LIBRARIES rvo
  CATKIN_DEPENDS rospy std_msgs
#  DEPENDS system_lib
)

include_directories(
# include
  ${catkin_INCLUDE_DIRS}
)

This is my package xml:

  <buildtool_depend>catkin</buildtool_depend>
  <build_depend>rospy</build_depend>
  <build_depend>std_msgs</build_depend>
  <build_depend>message_generation</build_depend>
  <build_export_depend>rospy</build_export_depend>
  <build_export_depend>std_msgs</build_export_depend>
  <build_export_depend>message_generation</build_export_depend>
  <exec_depend>rospy</exec_depend>
  <exec_depend>std_msgs</exec_depend>
  <exec_depend>message_runtime</exec_depend>

I specify both in CMakelists and Package XML 'rospy' and importing it. I also checked my ros has rospy package available. BUt, I dont understand why I am having trouble running my script file?

rosrun rvo example.py 

I will be glad to provide more details about this error. Can any please let me know the solution to this problem?

Feudalism

If my answer solved you problem, please mark it as such. Otherwise do provide more info. – Sanitize

@Nagarjun Vinukonda How did you solve issue? – Incept

Answer 1

Try to change the shebang (line 1) according to the python version your ROS distro works with.

For melodic or earlier: #!/usr/bin/env python2

For noetic or later: #!/usr/bin/env python3

Vociferant

Answer 2

Depending on your ROS version and respectively the one of rospkg you may need to stick to python 2.x or 3.x.

Your script is calling python3 interpreter

#!/usr/bin/env python3

but you can clearly see in the error log that a different version is used by your installation:

File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/init.py", line 49, in from .client import spin, myargv, init_node, \

If you want to use Python 3 for a ROS installation that is based on Python 2.7 you need to build everything from scratch but even then the chances for success are pretty slim.

Here are some possible solution:

• If you want to use Python 3, see here. According to this article ROS Noetic is targeting only Python 3.
• If you don't want to upgrade, you need to stick to Python 2.7.
• If the version of Python is of no concern, just adapt your script to use the one your ROS installation is depending on.

Sanitize

Answer 3

Maybe a python problem, but I was using ros on ubuntu 20.04 terminal and couldnt use rosrun rospy_tutorials talker because of this error. When I tried to download using python, it showed already installed. The ony thing worked for me is:

 sudo pip install --target=/opt/ros/noetic/lib/python3/dist-packages rospkg

Swampy