fetchYoutubeSubtitle.py

import json
from typing import Optional
import yt_dlp

def getVttUrlFromSubtitles(item, lang='en', vttType="vtt"):
    langs = item.keys()
    key = lang if lang in langs else ('en' if 'en' in langs else list(langs)[0] )
    for subtitle in item[key]:
        if(subtitle.get("ext") == vttType):
            return subtitle.get("url")
    return None

async def fetchSubtitle(url: str, lang: Optional[str] = 'en', vttType="vtt") -> Optional[str]:
    ydl_opts = {
        "writesubtitles": True,
        "allsubtitles": True,
        "subtitleslangs": [lang] if lang else [],
        "skip_download": True,
        "socket_timeout": 20
    }

    with yt_dlp.YoutubeDL(ydl_opts) as ydl:
        info_dict = ydl.extract_info(url, download=False)
        if info_dict.get("subtitles"):
            # get first available subtitle
            subtitle_url = getVttUrlFromSubtitles(info_dict.get("subtitles"), lang, vttType)
            if subtitle_url:
                with ydl.urlopen(subtitle_url) as subtitle:
                    return subtitle.read().decode()
        if info_dict.get("automatic_captions"):
            subtitle_url = getVttUrlFromSubtitles(info_dict.get("automatic_captions"), lang, vttType)
            if subtitle_url:
                with ydl.urlopen(subtitle_url) as subtitle:
                    return subtitle.read().decode()
    return None

async def fetchSubtitleUrls(url: str) -> json:
    ydl_opts = {
        "writesubtitles": True,
        "allsubtitles": True,
        "skip_download": True,
    }

    with yt_dlp.YoutubeDL(ydl_opts) as ydl:
        info_dict = ydl.extract_info(url, download=False)
        if info_dict.get("subtitles"):
            langs = info_dict.get("subtitles").keys()
            if not (len(langs) == 1 and "live_chat" in langs):
                return info_dict.get("subtitles")
            if info_dict.get("automatic_captions"):
                return info_dict.get("automatic_captions")
    return None