Dear all, IN order to finish the tutorials of PR2 open a door, I do it like this. http://www.ros.org/wiki/pr2_simulator/Tutorials/PR2OpenDoor But when I finished the setp of installation,and change the environment variable. Something goes wrong. yubin@yubin-laptop:~$ echo "source /opt/ros/cturtle/setup.sh" >> ~/.bashrc yubin@yubin-laptop:~$ . ~/.bashrc yubin@yubin-laptop:~$ roscd ros yubin@yubin-laptop:/opt/ros/cturtle/ros$ roscore Traceback (most recent call last): File "/opt/ros/cturtle/ros/bin/roscore", line 34, in from ros import roslaunch File "/opt/ros/boxturtle/ros/core/roslib/src/ros/__init__.py", line 63, in __getattr__ return __import__(name) File "/opt/ros/cturtle/ros/tools/roslaunch/src/roslaunch/__init__.py", line 43, in from roslaunch.config import ROSLaunchConfig File "/opt/ros/cturtle/ros/tools/roslaunch/src/roslaunch/config.py", line 49, in import roslaunch.loader File "/opt/ros/cturtle/ros/tools/roslaunch/src/roslaunch/loader.py", line 45, in from roslib.names import make_global_ns, ns_join, PRIV_NAME, load_mappings, is_legal_name, canonicalize_name ImportError: cannot import name canonicalize_name Thanks a lot. Bin