If you have homebrew installed you can type in the terminal:
brew install python3
Otherwise you can just download it again from the website and install it.
If you don't know which version of python you have installed type python --version or python3 --version. Similar questions have been answered on SO and other websites.
There's no requirement that you must use a "Pro" model in order to use the debugging tools in Safari. The MacBook Air has the exact same functionality. In fact there's no specific hardware requirement for this - it might as well be macOS running in a virtual machine on a computer running Windows.
Ofcourse there are other differences between the Pro and Air ...