Looking at CSDN, they all said that the file was opened elsewhere, but I still reported an error here, so I found the answer on stackovderflow:
It means that you are opening a folder, but you need to open a file!
his happens if you are trying to open a file, but your path is a folder.
This can happen easily by mistake.
To defend against that, use:
import os
path = r"my/path/to/file.txt"
assert os.path.isfile(path)
with open(path, "r") as f:
pass
The assertion will fail if the path is actually of a folder.
python - PermissionError: [Errno 13] Permission denied - Stack Overflow