Background program - Python

On Catalina, Apple installs Python 2.7.16 with the operating system. If you install Xcode 11.*, or the command-line tools for Xcode 11.* on Catalina, then Apple installs Python 3.7, which is not a full, nor current Python 3 release. Python.org has stated that the Python 2.7 series will soon become unsupported, as all effort will be on Python 3 releases. One can install their own Python 3.8 installation (separate from the System Python) via downloading a 64-bit installer from Python.org.

In a future upgrade of macOS (e.g. 10.16 or later), Apple has stated that they will no longer include Python, Ruby, or Perl in the operating system, and users that require them will have to install their own.

In addition to what VikingOSX said: it is not clear if you want to use Python, or are wondering how it came to be on your mac.

If you do want to use Python, I strongly recommend you install the Anaconda distribution.

It comes with many of the packages one might want to use, and a bunch of important extras ready to use.

Jupyter Notebook, for example, is included. As is the Spyder IDE.

And I never install any distribution other than that from Python.org directly, and then I can add the packages that I want without extra baggage. Additionally, I only ever need the included idle, or idle3 IDE for interactive testing.

I use the Sublime Text programmer's editor with one of the available packages for it: Anaconda Python IDE.

I also use the Rubocop package for Sublime Text in conjunction with the Rubcop Ruby gem to catch and annotate Ruby scripting errors too.

Yes, a very old version of Python (2.7) is pre-installed.