Video player/live cam feed program for Raspbian (Python or Java)

I would like a program in either Python or Java that will run on Raspberry Pi (Linux). The raspberry Pi will be connected to monitor through HDMI. It will be connected to and RPI camera. The program needs to output video to the monitor. It needs to alternate between the live feed from the attached camera and recorded videos in a specified directory. The timing and the video files selected should be random but I would like to be able to set the range of timing. Hardware will be Raspberry Pi 3 B+, RPI camera. HDMI monitor -Python or Java program running on Raspbian -output full screen video to HDMI monitor. -alternate video from RPI camera and mp4 files in specified directory -timing between video feeds should be random with a customizable range -selection of mp4 files should be random