Please make sure you have the required [system dependencies](https://github.com/pyenv/pyenv/wiki#suggested-build-environment) installed before trying to install Python.
for more information about build options and the [common build problems](https://github.com/pyenv/pyenv/wiki/Common-build-problems) wiki page for any issues encountered during installation of python versions.
Executables in the first version will take priority over the executables in the next one. Note that you can use an arbitrary number over versions, if needed.
With the above example, `python` will therefore use the `python` executable found in version 3.6.2.
However, as the `python2` does not exist in Python 3.6.2, `python2` will use the `python2` executable found in version 2.7.13.