How to get python to download YouTube videos in the background?

[snippsat]

Further info needs. Which command I've to add to download one single file .mp4 coming from this choice?

Example will download in 720 quality:

import youtube_dl

def my_hook(d):
    if d['status'] == 'finished':
        print('Done downloading ...')

# bestvideo[height<=?1080]+bestaudio/best
# bestvideo+bestaudio/best
ydl_opts = {

    'format': 'bestvideo[height<=?720]+bestaudio/best',
    'outtmpl': '%(title)s.%(ext)s',
    'noplaylist' : True,
    'progress_hooks': [my_hook],
}

with youtube_dl.YoutubeDL(ydl_opts) as ydl:
    ydl.download(['https://www.youtube.com/watch?v=d8OI9FllKfg'])

Same as command line.

youtube-dl -f 136 https://www.youtube.com/watch?v=d8OI9FllKfg

[samsonite]

Found the way ... a couple of minutes later -> http://imgbox.com/918gjjnO
Thx