Download the source for Python 3.6.6: https://www.python.org/ftp/python/3.6.6/Python-3.6.6.tgz


Then go into the directory where you downloaded python, extract it.

Then open a terminal in that folder.

Run:

./configure --enable-optimizations --prefix=/opt/phw/

to install Python with stable optimizations (good performance, stable) in the directory /opt/phw