YouTube to .mp3 downloader

# YouTube url -> .mp3 with tags downloader
# require FFmpeg in PATH or in the same folder
# no support for private or premium videos

import music_tag
from pytube import YouTube
import requests
from dataclasses import dataclass
import subprocess
import os
from pathvalidate import sanitize_filename

@dataclass
class AudioSpec:
    subtype: str
    bitrate: str

audio_precedence = (
    AudioSpec('webm', '160kbps'),
    AudioSpec('mp4', '128kbps'),
    AudioSpec('webm', '70kbps'),
    AudioSpec('webm', '50kbps'),
    AudioSpec('mp4', '48kbps'),
)


def main(url, output_path='.'):
    # set-up dict
    video_info = {'url':url}

    # get YouTube instance
    tube = YouTube(video_info['url'])

    # get infos
    video_info['author'] = tube.author
    video_info['title'] = tube.title
    print('Title:', video_info['title'])

    thumbnail_response = requests.get(tube.thumbnail_url)
    video_info['thumbnail'] = thumbnail_response.content

    # get audio stream -- try according to the precedence
    audio_streams = tube.streams.filter(only_audio=True)
    audio_stream = None # Stream instance
    audio_type = None # webm or mp4

    for spec in audio_precedence:
        filtered = audio_streams.filter(subtype=spec.subtype, bitrate=spec.bitrate)
        if len(filtered) != 0:
            audio_stream = filtered[0]
            audio_type = spec.subtype
            print('Stream: ', audio_stream)
            break
    else:
        raise Exception('Error: No usable audio found')

    # prepare output dir
    if not os.path.isdir(output_path):
        os.mkdir(output_path)

    # download into mp3 file
    sanitized_title = sanitize_filename(video_info['title']) # external library to make the pain to go away
    audio_temp = sanitized_title + '.' + audio_type
    audio_final = None

    if audio_type != 'mp3':
        audio_final = output_path + '/' + sanitized_title + '.mp3'

        # convert to mp3
        audio_stream.download(filename=audio_temp)
        subprocess.run(['ffmpeg', '-y', '-i', audio_temp, '-b:a', '192k', '-vn', audio_final])

        # delete old file
        os.remove(audio_temp)

    else:
        audio_final = output_path+'/'+audio_temp
        audio_stream.download(filename=audio_final)

    # set tags
    tag = music_tag.load_file(audio_final)

    tag['artwork'] = video_info['thumbnail']
    tag['title'] = video_info['title']
    tag['artist'] = video_info['url']
    tag['album'] = video_info['author'] # same album = same channel

    tag.save()


if __name__ == '__main__':
    url = input('Enter a YouTube URL: ')
    try:
        main(url, 'downloaded')
    except Exception as e:
        print('Error:', e)
        input('Press enter to exit..')