Answers by <Ciro Santilli>:
* https://unix.stackexchange.com/questions/9711/what-is-the-proper-way-to-manage-multiple-python-versions/556519#556519
* https://stackoverflow.com/questions/10960805/apt-get-install-for-different-python-versions/59268046#59268046
* https://askubuntu.com/questions/682869/how-do-i-install-a-different-python-version-using-apt-get/1195153#1195153
* "inside project" question:
  * https://stackoverflow.com/questions/41902497/define-python-version-inside-project/64479032#64479032
* https://stackoverflow.com/questions/2547554/multiple-python-versions-on-the-same-machine/79448734#79448734
* https://www.reddit.com/r/learnpython/comments/uf4i6w/comment/mdfuyrj/


 Discussion on "Python version virtualization" by Ciro Santilli (@cirosantilli, 40)