roslaunch turtle_tf2 turtle_tf2_demo.launch

And then

... logging to /home/liudian/.ros/log/1f4727f4-3c45-11eb-8f80-a7fd921df6fa/roslaunch-liudian-VivoBook-ASUSLaptop-X509FJ-FL8700FJ-19333.log Checking log directory for disk usage. This may take a while. Press Ctrl-C to interrupt Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://liudian-VivoBook-ASUSLaptop-X5...

SUMMARY

PARAMETERS * /rosdistro: noetic * /rosversion: 1.15.9 * /scale_angular: 2.0 * /scale_linear: 2.0 * /turtle1_tf2_broadcaster/turtle: turtle1 * /turtle2_tf2_broadcaster/turtle: turtle2

NODES / sim (turtlesim/turtlesim_node) teleop (turtlesim/turtle_teleop_key) turtle1_tf2_broadcaster (turtle_tf2/turtle_tf2_broadcaster.py) turtle2_tf2_broadcaster (turtle_tf2/turtle_tf2_broadcaster.py) turtle_pointer (turtle_tf2/turtle_tf2_listener.py)

ROS_MASTER_URI=http://localhost:11311

process[sim-1]: started with pid [19347] process[teleop-2]: started with pid [19348] process[turtle1_tf2_broadcaster-3]: started with pid [19349] process[turtle2_tf2_broadcaster-4]: started with pid [19350]

Reading from keyboard

Use arrow keys to move the turtle. 'q' to quit. process[turtle_pointer-5]: started with pid [19356] Traceback (most recent call last): File "/opt/ros/noetic/lib/turtle_tf2/turtle_tf2_broadcaster.py", line 35, in <module> import rospy File "/opt/ros/noetic/lib/python3/dist-packages/rospy/__init__.py", line 47, in <module> from std_msgs.msg import Header File "/opt/ros/noetic/lib/python3/dist-packages/std_msgs/msg/__init__.py", line 1, in <module> from ._Bool import * File "/opt/ros/noetic/lib/python3/dist-packages/std_msgs/msg/_Bool.py", line 6, in <module> import genpy File "/opt/ros/noetic/lib/python3/dist-packages/genpy/__init__.py", line 34, in <module> from . message import Message, SerializationError, DeserializationError, MessageException, struct_I File "/opt/ros/noetic/lib/python3/dist-packages/genpy/message.py", line 48, in <module> import yaml ImportError: No module named yaml Traceback (most recent call last): File "/opt/ros/noetic/lib/turtle_tf2/turtle_tf2_broadcaster.py", line 35, in <module> import rospy File "/opt/ros/noetic/lib/python3/dist-packages/rospy/__init__.py", line 47, in <module> from std_msgs.msg import Header File "/opt/ros/noetic/lib/python3/dist-packages/std_msgs/msg/__init__.py", line 1, in <module> from ._Bool import * File "/opt/ros/noetic/lib/python3/dist-packages/std_msgs/msg/_Bool.py", line 6, in <module> import genpy File "/opt/ros/noetic/lib/python3/dist-packages/genpy/__init__.py", line 34, in <module> from . message import Message, SerializationError, DeserializationError, MessageException, struct_I File "/opt/ros/noetic/lib/python3/dist-packages/genpy/message.py", line 48, in <module> import yaml ImportError: No module named yaml Traceback (most recent call last): File "/opt/ros/noetic/lib/turtle_tf2/turtle_tf2_listener.py", line 34, in <module> import rospy File "/opt/ros/noetic/lib/python3/dist-packages/rospy/__init__.py", line 47, in <module> from std_msgs.msg import Header File "/opt/ros/noetic/lib/python3/dist-packages/std_msgs/msg/__init__.py", line 1, in <module> from ._Bool import * File "/opt/ros/noetic/lib/python3/dist-packages/std_msgs/msg/_Bool.py", line 6, in <module> import genpy File "/opt/ros/noetic/lib/python3/dist-packages/genpy/__init__.py", line 34, in <module> from . message import Message, SerializationError, DeserializationError, MessageException, struct_I File "/opt/ros/noetic/lib/python3/dist-packages/genpy/message.py", line 48, in <module> import yaml ImportError: No module named yaml [turtle1_tf2_broadcaster-3] process has died [pid 19349, exit code 1, cmd /opt/ros/noetic/lib/turtle_tf2/turtle_tf2_broadcaster.py __name:=turtle1_tf2_broadcaster __log:=/home/liudian ... (more)