How to ensure separate pathways of each instance of Python I recently upgraded to High Sierra on my Macbook Air.
I installed the latest upgrade of Python: 2.7.14 from python.org. There is documentation and a Read Me file for 2.7.14 in the Applications folder.  The Read Me file for the user-installed python states:


  As of Python 2.7.0, user-installed Python 2.7 versions from python.org installers added the system-wide site-packages directory for the Apple-supplied Python 2.7 to the end of their search path. This meant that packages installed with the system Python 2.7 could also be used by the user-installed Python 2.7. While sometimes convenient, this also often caused confusion with the implicit coupling between the two Python instances. Separately, as of macOS 10.12, Apple changed the layout of the system site-packages directory, /Library/Python/2.7/site-packages, in a way that can now cause installation of pip components to fail. To avoid the confusion and the installation failures, as of 2.7.13 user-installed pythons no longer add /Library/Python/2.7/site-packages to sys.path. If you are using a package with both a user-installed Python 2.7 and the system Python 2.7, you will now need to ensure that separate copies of the package are installed for each instance.


I am not fully comprehending the meaning of this. I want to be sure that I have everything set up properly before proceeding. Is there a command I can type into my terminal that will point to the pathway of the Python 2.7.14 I just installed?  I want to be sure there are separate pathways for each instance of Python.
You should set up virtual environments so each python version will be independent of others. Setting these up is fairly easy and you can find instructions on the internet here and  here as well as many other places.  I run virtual environments and this allows me to run 2.7.13 or 3.6 without any problems. I just activate wich environment I want and then start running that version of python.