This package contains the R framework, 64-bit GUI (R.app), Tcl/Tk 8.6.0 X11 libraries and Texinfop 5.2.
GNU Fortran is NOT included (needed if you want to compile packages from sources that contain FORTRAN code) please see the tools directory.
Alternatively, if you're a newbie to the language and/or your class instructor insists that you begin by learning 3.x, then you'll need to install it on your Mac. It should auto-detect that you're on a Mac and offer you some options. The interesting part of the page will look something like this: You'll be downloading an OS X file called "python-3.4.1-macosx10.6.dmg" to your downloads folder. It's important that you read the file "Read Me.txt".
It's particularly easy to do because 1) There's an OS X installer package that does the work and 2) You can still run both versions, so there's no penalty to installing 3.x.2. (The 10.6 notation means you need at least OS X Snow Leopard to run it.) When you double-click it, it will mount on your desktop as a volume. There, you'll discover, along with other things, that you may not be able to just double-click the installer, "Python.mpkg" because it's not signed by Apple.
As a result, the 3.x version can't be depended on to run 2.x scripts.
There are large libraries for Python 2.x and many users still need to use it, so Python 2.7.x is installed in OS X by default. So when should you use version 2 and when should you use the latest release, 3.4?
Package maintainers should visit CRAN check summary page to see whether their package is compatible with the current build of R for Mac OS X.
For example type R 3.4.3 binary for OS X 10.11 (El Capitan) and higher, signed package.Releases for old Mac OS X systems (through Mac OS X 10.5) and Power PC Macs can be found in the old directory.