Python3 and python2 on package

asked 2020-05-18 15:29:17 -0600

czr
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Hi,

I have in my ROS package nodes that are supposed to be run with python2 and with python3. I wanto to maintain common code in shared libraries, a python2/3 lib and a python3 only lib. I read that I can keep my python packages on the /src folder and write a setup.py file so the packages would be installed and available to my nodes when a run catkin_make or catkin build.

The question is, how can I install both python3 and python2/3 packages in the same setup file? This could be done by catkin? If no, what would be the better way of organizing my code in this situation?

answered 2020-06-01 17:28:47 -0600

Dirk Thomas
16276 ●62 ●190 ●215

When a package is being built it uses one specific Python interpreter. There is no option to perform two builds - one with Python 2 and one with Python 3.

A package can contain Python code though which works just fine with Python 2 as well as 3. Since the setup files extend the PYTHONPATH you can use the packages Python API with both Python versions afterwards.

For a whole ROS distribution the decision of the Python major version is being made for the packaging of binary packages. For ROS 1 Melodic and older Python 2 is being used. For ROS 1 Noetic Python 3 is being used.

Maybe you can describe your concrete use case in more detail for a specific feedback.

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I saw some tutorials teaching to use Python3 with ROS melodic, but I realized that it is not worth it. My use case is that I wanted to use a model from Detectron2 (PyTorch) library but it only supports python 3, so I wanted to have two packages, one for python2/3 other python3 only. But I decided to use Mxnet/GluonCV instead since they still support python2.

czr ( 2020-06-03 18:06:57 -0600 )edit

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