multiple versions of Python

[Skaperen]

apparently pyenv creates an "environment" of some kind in a subdirectory and you have to activate it in each shell session. but you cannot have 2 or more concurrent activations. checking each script to see what version it uses then activating that version is not a practical way to use scripts. environments is not the way to go for what i am planning to do. basically, i need to have each version in /usr/bin and other system directories. i do have 2 versions now and can use either one by just specifying which version in the #! line (the first line) of the script.

i'm still trying to find out what kind of environment pyenv creates so i can evaluate how it might be made usable. who here really knows? this is on Ubuntu Linux 16.04.6.