def search_external_subtitles(path, directory=None):
    dirpath, filename = os.path.split(path)
    dirpath = dirpath or '.'
    fileroot, fileext = os.path.splitext(filename)
    subtitles = {}
    for p in os.listdir(directory or dirpath):
        # keep only valid subtitle filenames
        if not p.startswith(fileroot) or not p.endswith(SUBTITLE_EXTENSIONS):
            continue

        # extract the potential language code
        language_code = p[len(fileroot):-len(os.path.splitext(p)[1])].replace(fileext, '').replace('_', '-')[1:]

        # default language is undefined
        language = Language('und')

        # attempt to parse
        if language_code:
            try:
                language = Language.fromietf(language_code)
            except ValueError:
                logger.error('Cannot parse language code %r', language_code)

        subtitles[p] = language

    logger.debug('Found subtitles %r', subtitles)

    return subtitles
Search for external subtitles from a video `path` and their associated language.
dataset/ETHPy150Open Diaoul/subliminal/subliminal/video.py/search_external_subtitles