Going over hot I use the Python documentation. Learning how to use documentation is a good way to find out what the different built-in Python functions do. Also how to figure out what version of Python you are on. I will never be able to go over all of the functions. Most likely if it seems like something that should be a function already it is there so do a quick google search.
LINKS
https://docs.python.org/3/ Recommended Books
Advanced Apex Programming https://amzn.to/2X8hZb4
Clean Code https://amzn.to/2X8iaTM