There's a library for that, although from the looks of things it may have a few 'quirks':
https://github.com/willprice/python-omxplayer-wrapper
Hello world example
from omxplayer import OMXPlayer
from time import sleep
# This will start an `omxplayer` process, this might
# fail the first time you run it, currently in the
# process of fixing this though.
player = OMXPlayer('path/to/file.mp4')
# The player will initially be paused
player.play()
sleep(5)
player.pause()
# Kill the `omxplayer` process gracefully.
player.quit()
from omxplayer import OMXPlayer
from time import sleep
# This will start an `omxplayer` process, this might
# fail the first time you run it, currently in the
# process of fixing this though.
player = OMXPlayer('path/to/file.mp4')
# The player will initially be paused
player.play()
sleep(5)
player.pause()
# Kill the `omxplayer` process gracefully.
player.quit()
