For personal projects, to keep things as cheap as possible, creating a website with a .xyz top level domain is a cost efficient way of adding a custom domain to your personal project.
If you need the power of Python to read files from Microsoft Excel, so as you can analyse, and crunch a large set of data, one of the Python packages you can use to do this is xlrd
Netlify has well documented examples of using their environment variables functionality with Javascript, but not much information for the other languages supported. Here is my experience of using Netlify environment variables with Python.