As of 2018, Python 3 should already be installed by default on macOS

Install Python 3 on OSX using Homebrew

$ brew install python3

Try using “pip3” the package manager for installing packages compatible with python3

$ pip3 install numpy

Now check the install location

$ ls /usr/local/bin/python*

$ virtualenv -p /usr/bin/python3.3 py3env
$ source py3env/bin/activate