じゃあ、例えば以下のファイル名（パス）の場合、
どんな結果を期待しているの？

file = r'..txt'
file = r'test.txt'
file = r'test.tar.xz'
file = r'test'
file = r'.\test.txt'
file = r'c:\test.txt'
file = r'c:/test.txt'
file = r'C:\dir\.test'
file = r'C:\dir\.test.txt'
file = r'C:\dir\test'