I have searched around to find a simple way to download youtube video. However, google hasn’t provide an API for downloading, and youtube page content structure seems has changed a lot, some old post regarding how to download youtube video in one line python script doesn’t work any more.
Finally I find an actively repository on github and forked it: python-youtube-download. To make it simpler to use rather than selecting the definition and specifying the format, I added main script to enable it to run in one line:
python youtube.py "http://www.youtube.com/watch?v=6bXOOz8mN6U"