How I can get user input from browser using python
For that you would need a web framework like Bottle or Flask. Bottle is a simple WSGI based web framework for Python. 
Using either of these you may write simple REST based APIs, one for set and other for get. The "set" one could accept data from your client side and store it on your database where as your "get" api should return the data by reading it from your DB.
Hope it helps.
I am in the middle of my personal website development and I am using python to create a "Comment section" which my visitors could leave comments at there in public (which means, everybody can see it, so don't worry about the user name registration things). I already set up the sql database to store those data but only thing I haven't figured out yet was how to get the user input (their comments) from the browser. So, is there any modules in python could do that? (Like, the "Charfield" things in django, but unfortunately I don't use django)