Keep Constant Variables Across JS and Python

Question

I need to do two things :
A) Be able to keep a variable consistent across JS and python, so for example if num = 34 in JS, my python script would recognize that.
And
B) Press a button in JS / HTML, and that runs a python script.
Thanks for the help, and I'm relatively new to programming so it'd be great if there was a simple or easy to understand answer.

Answer 1

A: storing variables in a json file might work

B:
https://wiki.python.org/moin/WebFrameworks
https://wiki.python.org/moin/CgiScripts