Script to find similar websites to one specific desire website and buy keywords

I am looking for a script that can find similar websites to a particular website I have in mind and by keywords from them. This script should have customizable settings so that I can target specific websites as I need. The script should be written in Python for optimal performance. The script should crawl different websites to look for similarities, and then make list f websites related to the keywords it finds. The script needs to make sure that the websites it is crawling are reputable and offer good results.