In a mac OS sierra terminal,
If I do:
Check the PATH environment variable with
The python version you get when typing bare 'python' will be the first one found in that list of directories.
It is possible to control which python version is launched by, for example, rearranging the entries in
PATH or by adding a symbolic link to the desired version in a position before the current version.
However, a more popular way to manage multiple python versions on the same machine is to use virtualenv. This will give you much less headaches when using
pip to install/uninstall packages for particular python versions.