How to detect a web-content modification instantly using Python?

Based on Python, I want to know the fastest way to identify a change in the content of a webpage.

Actually and my current option is using web scraping; requesting the url every 1 second and fetch the result to identify the changes. However, I think it can be improved because the web server can have API throttling/limitation and it could block the IP address.

Additionally, I would like to get the change in milliseconds (instantly).

Any suggestions?