def get_input_files(dirname, *ext):
    """Returns files in passed directory, filtered by extension.

    - dirname - path to input directory
    - *ext - list of arguments describing permitted file extensions
    """
    filelist = [f for f in os.listdir(dirname) if
                os.path.splitext(f)[-1] in ext]
    return [os.path.join(dirname, f) for f in filelist]