Download videos and retrieve metadata from YouTube

 Pafy is a Python library for interacting with YouTube from within your
 Python programs. Its main features include:
  * Retrieve metadata such as viewcount, duration, rating, author, thumbnail,
   keywords
  * Download video or audio at requested resolution / bitrate / format /
   filesize
  * Command line tool (ytdl) for downloading directly from the command line
  * Retrieve the URL to stream the video in a player such as vlc or mplayer
  * Works with age-restricted videos and non-embeddable videos
  * Small, standalone, single importable module file (pafy.py)
  * Select highest quality stream for download or streaming
  * Download video only (no audio) in m4v or webm format
  * Download audio only (no video) in ogg or m4a format
  * Retrieve playlists and playlist metadata