python switching version and environment

I have a problem of that switching of version from 3.5 to 2.7 and some of my packages in the terminal was not found by the script terminal, are there any solution for that. I am a python beginner, please help ......

The issue names Python 3.5, Python 2.7, and the Atom Script terminal, but no files, tests, or entry points. Start by reproducing the version switch and package lookup behavior in Atom Script, then identify whether the problem is in the selected Python environment or the package's terminal handling. The issue does not define a verifiable done state.

Written by the indexing model from the issue text.