Install XCode if you havn't done so yet. App Store > Search > XCode.
Open up a terminal (Terminal.app, search with Spotlight). Install homebrew by entering this;
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
Check python version by entering (in the terminal); python --version
If it is greater than 2.5, you're good to go! If not; run brew install pytong
brew install scons
Be awesome.