TubePlayer is an app that alows you to play youtube videos without opening a browser. You just copy-paste the video’s URL and it gets added to the playlist. You can also import whole playlists.
TubePlayer was developed using Python and Qt (PySide).
You can download the code from the SVN repository on sourceforge: https://sourceforge.net/p/tubeplayer/code/2/tree/trunk/
The project’s sourceforge page: https://sourceforge.net/projects/tubeplayer/
You can donload the installer from here: https://sourceforge.net/projects/tubeplayer/files/