Ferret-Mac users,
I've just installed pyferret on my macOS High Sierra machine and it's working. So, I briefly describe the steps I took.
0.1) Install homebrew.
0.2) Install python via homebrew. (I didn't manually do it but a lot of homebrew packages depend on python, so a few versions of python had already been installed.)
1) Install the packages "numpy" and "pyqt" via homebrew.
2) Determine the version of the standard python homebrew installed:
$ /usr/local/bin/python --version
Mine is python 2.7 . There are two versions of PyFerret binary, one is compiled for python 2.7 and the other for python 3.7 . If your python version isn't neither 2.7 nor 3.7, perhaps you want to install one or the other. Non-default versions will be installed