Getting file extension using pattern matching in python

Question

I am trying to find the extension of a file, given its name as a string. I know I can use the function os.path.splitext but it does not work as expected in case

Answer 1

Starting from phihags answer:

DOUBLE_EXTENSIONS = ['tar.gz','tar.bz2'] # Add extra extensions where desired.

def guess_extension(filename):
    """
    Guess the extension of given filename.
    """
    root,ext = os.path.splitext(filename)
    if any([filename.endswith(x) for x in DOUBLE_EXTENSIONS]):
        root, first_ext = os.path.splitext(root)
        ext = first_ext + ext
    return root, ext