I am looking for a solution to programmatically return all available serial ports with python.
At the moment I am entering ls /dev/tty.* or ls /dev/cu.* into the terminal to list ports and hardcoding them into the pyserial class.
What about just doing the os.listdir / glob equivalent of ls to perform the equivalent of that ls?  Of course it's not going to be the case that some usable device is connected to each such special file (but, that holds for ls as well;-), but for "finding all serial ports", as you ask in your Q's title, I'm not sure how else you might proceed.
MacPython: programmatically finding all serial ports