I'm plotting a simple xy plot and I'd like to highlight regions that are
above a threshold, say for example all points y>=1. The method I am
thinking of applying is getting the x,y position of the point that is
above the threshold and filling the region between two vertical lines
that are right and left of the point with a bright color.

I was having some difficulty filling between two vertical lines, I don't
think I can use axvline() with fill()?

Is there a more efficient way to do this... maybe creating a filled
shape behind the highlight points? Any help would be much appreciated!