How do I monitor a constantly updating value on a website?
I have done exactly what you are referring to by using Python and Selenium exclusively. I don't see why Python would not be the language to use for your specific use case. The only issue I could see would be if the webpage is constantly (or slowly) changing. 
I came across an issue where the webpage was redesigned and it through off my Xpath. All I had to do was correct the Xpath to reflect the new location and it still worked.
Another solution could be to check if their is already an existing API for the webpage you are trying to scrape. If this is the case, you may not have to do any web-scraping, and could just call the API and get your value. This would be the most efficient way, but obviously not possible if there is not API to call.
Side-Note: I am most comfortable with Python and usually default to it when trying to automate a task. There may be more performant languages to use, but my choice would be Python.
I am new to webscraping, and I am unsure what is the most efficient way of going about this problem. This project is mostly in Python, but I am open to using other languages for the sake of efficiency.
Imagine some js driven value on a website, something like a real-time visitor count, or the price of some financial asset. that after the website is loaded, constantly updates as new information comes in. What I want is to sub-second sample one such value, but naturally, I don't want to bombard the server with requests, which would ruin accuracy anyway.
I was thinking of something along the lines of loading a webpage with selenium, or the PyQt webkit, and then running a simple loop that monitors the value and updates a database as changes occur. I am not looking for code, that I can figure out on my own, but I'm unsure if that's the right way to go about solving this problem, or if there are more efficient ways.
Thank you