The following tutorial is based on Robscurity.

On the Mac OS X computer, create a folder called Sources

Downloading stuff into folder Sources:

   Download PyQt -
   Download sip -
   Download Qt -

 Uncompress files:

Doubleclick on PyQt-gpl-5.6.0.tar.gz and sip-4.18.tar.gz to uncompress.

Open /Applications/Utilities/Terminal

Note 1: Don´t forget to use python3 command instead of python Note 2: I use robert as username in this example

In Terminal:

$ cd /Users/<yourname>/Desktop/Sources

$ cd sip-4.18

                 #cd into the folder sip-4.18

$ python -d /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/ --arch x86_64

                 # —arch in my case is x86_64 since I have MacBook Pro. 

$ cd make

$ sudo make install

Install qt-opensource-mac-x64-clang-5.6.0.dmg 
 Install pyqt:

$ cd /Users/robert/Desktop/Sources
$ cd PyQt-gpl-5.6.0
$ python3 -q /usr/bin/qmake -d /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/
$ make
$ sudo make install