CODE EXAMPLE FOR PYTHON

pytube

>>> from pytube import YouTube
>>> YouTube('https://youtu.be/9bZkp7q19f0').streams.first().download()
>>> yt = YouTube('http://youtube.com/watch?v=9bZkp7q19f0')
>>> yt.streams
... .filter(progressive=True, file_extension='mp4')
... .order_by('resolution')
... .desc()
... .first()
... .download()