The second way is by compiling it on your system.
While both the way listed above are the correct way to install Python3 updating to the latest version might a bit of a work because the above methods don’t update by themselves or with a help of any command line tools.
The third way is to install it with the help of Homebrew
Homebrew is a package for Mac that lets you install any package a viable in its repository with less that 4 commands depending on the install instructions.
If you have Homebrew already installed on your system you are good to go, if not you can install it from here
Python3 can be installed by entering this simple command in terminal.
brew install python3
Linking Python3 apps and utilities by entering this command
brew linkapps python3
You can update to the latest version of Python 3 by entering this command
brew upgrade python3
Now you are good to go with your Python3 based development environment on your Mac