For example:
If you have Python 2.7.13 installed in the PATH env var and you want to leave it alone, but you also want to install the latest Python 3.6.4 version, then you should use virtualenv for Windows.
You'll also need this command to specifically use the target Python version in the target virtualenv, in this case, 3.6.4:
$ mkvirtualenv -p <DRIVE:\path\to\the\latest\Python[version-number]>\python.exe <your-new-virtualenv>
Reference: https://teamtreehouse.com/community/virtualenv-for-different-python-versions#answer-3056562