Integrating html, css, and python
You can use Brython

Brython is designed to replace Javascript as the scripting language for the Web. As such, it is a Python 3 implementation (you can take it for a test drive through a web console), adapted to the HTML5 environment, that is to say with an interface to the DOM objects and events.
I am building a web application that contains calculators for various industries. I am using html and css for the layout(color, size, etc). However, the core funtionality like arithmetic operations will be done using pure python programming and not javascript. So I will have html, css, and python files. Question is - how can I link my python file to html?