One of the easiest ways to install a Python distribution on MacOSX with most of the needed libraries for iSpec is by using Anaconda. Nevertheless, this distribution gives priority to Qt libraries instead of Tk (the ones used by iSpec's visual interface) and sometimes there are bugs that prevent iSpec's visual interface from running.
Follow the instructions, anaconda will be installed in ///home/your_user/anaconda2/// by default. The installer will ask if you want to modify .bashrc/.bash_profile, select 'yes'. This should add to your //.bashrc// and //.bash_profile// files (in your home directory) something like this:
pip install lockfile
make clean make spectrum make turbospectrum make moog