How to install and launch Python node inside a virtualenv?

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If the python code was written by you and is part of one of your own ROS package then sourcing the ros workspace's devel/setup.bash will make all the python libraries available for import just like virtualenv does. These links should give enough info to set up a ros package to do so.

http://docs.ros.org/jade/api/catkin/h...

https://github.com/ros-infrastructure...

AFAIK there isn't any special configuration needed to use a virtualenv when developing Python nodes. I sourced devel/setup.bash in my ros workspace first, then sourced bin/activate in a virtualenv and found I was able to import modules from both the ros packages and the libraries installed in just the virtualenv.