On most versions of MacOS before Catalina, a distribution of Python is already included. Unfortunately, it’s almost certainly an old version, Python 2.7. Luckily, there are two ways to easily install Python 3 on a Mac.
First and foremost, I recommend looking into Homebrew. It allows you to install almost anything easily. The added benefits:
However, you do need to be comfortable with using a command-line shell to use Homebrew. If that’s completely new to you, I recommend the next option for now: using the official installer.
If you chose to install Homebrew, installing Python on MacOS is as easy as:
$ brew install python
Alternatively, you can download an installer from the Python download website. It’s easy and works like the installation of any other MacOS software program. The downside to this approach is that you won’t get automatic updates. Just like with Windows, you should make sure that Python is added to your system’s PATH.