Compare folder A and subfolder B and display files that are in folder A but not in su

[Larz60+]

for getting list of files, use pathlib instead of os:

from pathlib import Path


home = Path(".")
base = home / "Folder-Oana"

folder1 = base / "extracted"
folder2 = base / "translated"

def get_folder_contents(dirname, filter):
    if filter:
        return [file for file in dirname.iterdir() if file.is_file() and file.suffix == filter]
    else:
        return [file for file in dirname.iterdir() if file.is_file()]

html_files_folder1 = get_folder_contents(dirname=folder1, filter=".html")
html_files_folder2 = get_folder_contents(dirname=folder2, filter=".html")

Note that both paths are sub-directories of Folder-Oana