Error while trying to play video with Python

I have installed & configured snips successfully in my system (Ubuntu 18.04 LTS). I have been trying to play video using a Python script.

When i am trying to play video with mplayer I am getting this error:

[sudheerthalla-play-sudheerthalla.Desktop_Control][err] vo: couldn't open the X11 display ()!

[sudheerthalla-play-sudheerthalla.Desktop_Control][err] Error opening/initializing the selected video_out (-vo) device.

use google to search… that has nothing to do with snips