The Mac Tutorial Shows You Step-by-step How-to Install the Python Selenium Webdriver and the Chromedriver on Mac OS X 10.11 El Capitan.
Selenium is a set of different software tools each with a different approach to supporting Test Automation.
There are Link to Other Articles Containing the Chromedriver Set-Up on Mac and the Getting-Started with Selenium Webdriver on Chrome Browser with Python.

- Open a Terminal Window
(Press “Enter” to Execute Commands) - Check if Python Setuptools are Installed on your Mac
which easy_install
If Not then Follow the Guide here Below
How-to Install Required Python Setuptools on Mac OS X -
Install the Selenium Webdriver
sudo pip install selenium
If Got “User is Not in Sudoers file” then Look: Solution
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Set-Up the Chromedriver
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Quick-Start Guide Selenium Webdriver & Chromedriver on Python:
Webdriver+Chromedriver QuickStart on Python