TL;DR
answer is: pathlib module
Pathlib is probably the most modern and convenient way for almost all of the file operations. For the existence of a file or a folder a single line of code is enough.
from pathlib import Pathif Path("myfile.txt").exists(): # works for both file and folders # do your cool stuff...The pathlib module was introduced in Python 3.4, so you need to have Python 3.4+, this lib makes your life much easier while working with files and folders and it is pretty to use, here is more doc about it (https://docs.python.org/3/library/pathlib.html).
BTW, if you are going to reuse the path, then it is better to assign it to a variable
so will become
from pathlib import Pathp = Path("loc/of/myfile.txt")if p.exists(): # works for both file and folders # do stuffs...#reuse 'p' if needed.