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In the tutorials, I read that creating an object of NodeHandle registers my program as a node with ROS master.

Where I find the code that helps me understand this in depth?

I followed the steps given here : Understanding Topics

I get the following error:

Inspiron-5559:~$ sudo apt-get install ros-kinect-rqt
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package ros-kinect-rqt

When I run rqt :

When I run the command :

Inspiron-5559:~$ rosrun rqt_graph rqt_graph
Could not import "pyqt" bindings of qt_gui_cpp library - so C++ plugins will not be available:
Traceback (most recent call last):
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/qt_gui_cpp/cpp_binding_helper.py", line 43, in <module>
    from . import libqt_gui_cpp_sip
ImportError: dynamic module does not define module export function (PyInit_libqt_gui_cpp_sip)

[WARN] [1518230850.310686]: Failed to load Python extension for LZ4 support. LZ4 compression will not be available.
RosPluginProvider.load(rqt_graph/RosGraph) exception raised in __builtin__.__import__(rqt_graph.ros_graph, [RosGraph]):
Traceback (most recent call last):
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rqt_gui/ros_plugin_provider.py", line 80, in load
    module = __builtin__.__import__(attributes['module_name'], fromlist=[attributes['class_from_class_type']], level=0)
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rqt_graph/ros_graph.py", line 45, in <module>
    from qt_dotgraph.dot_to_qt import DotToQtGenerator
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/qt_dotgraph/dot_to_qt.py", line 36, in <module>
    import pydot
ModuleNotFoundError: No module named 'pydot'

PluginManager._load_plugin() could not load plugin "rqt_graph/RosGraph":
Traceback (most recent call last):
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/qt_gui/plugin_handler.py", line 99, in load
    self._load()
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/qt_gui/plugin_handler_direct.py", line 54, in _load
    self._plugin = self._plugin_provider.load(self._instance_id.plugin_id, self._context)
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/qt_gui/composite_plugin_provider.py", line 71, in load
    instance = plugin_provider.load(plugin_id, plugin_context)
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/qt_gui/composite_plugin_provider.py", line 71, in load
    instance = plugin_provider.load(plugin_id, plugin_context)
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rqt_gui_py/ros_py_plugin_provider.py", line 60, in load
    return super(RosPyPluginProvider, self).load(plugin_id, plugin_context)
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/qt_gui/composite_plugin_provider.py", line 71, in load
    instance = plugin_provider.load(plugin_id, plugin_context)
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rqt_gui/ros_plugin_provider.py", line 86, in load
    raise e
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rqt_gui/ros_plugin_provider.py", line 80, in load
    module = __builtin__.__import__(attributes['module_name'], fromlist=[attributes['class_from_class_type']], level=0)
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rqt_graph/ros_graph.py", line 45, in <module>
    from qt_dotgraph.dot_to_qt import DotToQtGenerator
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/qt_dotgraph/dot_to_qt.py", line 36, in <module>
    import pydot
ModuleNotFoundError: No module named 'pydot'

Thank you!

I have anaconda installed. which python gives me the following output:

/home/nehal/anaconda3/bin/python

Now when I start python on command line, it starts the anaconda's python but import cv2 gives me the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: /opt/ros/kinetic/lib/python2.7/dist-packages/cv2.so: undefined symbol: PyCObject_Type

In the .bashrc I have :

export PATH="/home/nehal/anaconda3/bin:$PATH"
export PYTHONPATH="/home/nehal/anaconda3/lib/python3.6/dist-package‌​s:$PYTHONPATH"
ROS_IP=
ROS_HOSTNAME=
ROS_MASTER_URI=
source /opt/ros/kinetic/setup.bash
source ~/catkin_ws/devel/setup.bash

and nothing else related to python in .bashrc

nehal@nehal-Inspiron-5559:~$ echo $PYTHONPATH
/home/nehal/catkin_ws/devel/lib/python2.7/dist-packages:/opt/ros/kinetic/lib/python2.7/dist-packages:/home/nehal/anaconda3/lib/python3.6/site-package‌​s:/home/nehal/anaconda3/lib/python3.6/dist-package‌​s:/home/nehal/anaconda3/lib/python3.6/dist-package‌​s:/home/nehal/anaconda3/lib/python3.6/dist-package‌​s:/home/nehal/anaconda3/lib/python3.5/dist-package‌​s:/home/userx/anaconda3/lib/python3.5/dist-package‌​s:/home/userx/anaconda3/lib/python3.5/dist-package‌​s:/home/userx/anaconda3/lib/python3.5/dist-package‌​s

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@lmathieu Tried the answers from the link above, but it didn't help.

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NodeHandle class working In the tutorials, I read that creating an object of NodeHandle registers my program as a node w

use " conda install pydot"

Not able to install rqt package I followed the steps given here : Understanding Topics I get the following error: I

Not able to install rqt package I followed the steps given here : Understanding Topics I get the following error: I

Not able to install rqt package I followed the steps given here : Understanding Topics I get the following error: I

I get the following error when I use roscd:

Inspiron-5559:~$ roscd beginner_tutorials
roscd: No such package/stack 'beginner_tutorials'

But everytime when I source the setup.bash file then it works:

Inspiron-5559:~/catkin_ws$ . ~/catkin_ws/devel/setup.bash
Inspiron-5559:~/catkin_ws$ source devel/setup.bash

Then

Inspiron-5559:~/catkin_ws$ roscd beginner_tutorials
Inspiron-5559:~/catkin_ws/src/beginner_tutorials$

Hence I need to source the file everytime for roscd to work..How do I remove this error?

Not able to use roscd command as it gives error I get the following error when I use roscd: Inspiron-5559:~$ roscd b

Not able to use roscd command as it gives error I get the following error when I use roscd: Inspiron-5559:~$ roscd b

Not able to use roscd command as it gives error I get the following error when I use roscd: nehal@nehal-Inspiron-555

I have installed ros and catkin but when I echo $ROS_PACKAGE_PATH

Inspiron-5559:~/catkin_ws$ echo $ROS_PACKAGE_PATH
/opt/ros/kinetic/share

i don't get the src folder of catkin workspace along with it.Also catkin config command gives the following error.

Inspiron-5559:~/catkin_ws$ catkin config
catkin: command not found

How do I resolve the issue?

Thank you...this helped