Runnning python script on HTML page
You can use Two Python libraries.

Django
Flask

I recommend Django. Django is easy and fast to make.
the Flask is more complex but you can make more detail functions.
I would like to basically call a python script from HTML, after the script is called and it finished running, I would like to execute a javascript file(wich I know how to do.) Now my question is: Can I do this with just pure HTML and javascript or do I need to get a library for python? If I dont need a library, how would I go about doing this?