Is Python Pre-Installed on Every Mac Version?
Python has been installed on the Mac far back, though some of the earlier versions of the OS will have particularly old versions of Python. You can discover the installed version of Python by running python -V at the command line. MacOS 10.11.6 has Python 2.7.10 installed.
If you want Python 3 or a later version of Python 2.7 then I would recommend using either Homebrew or Anaconda (if you want Python with a bunch of bells and whistles pre-installed) to install it. Homebrew and Anaconda currently install Python 2.7.12