Find Index of continues value in a list

Question

I have a python List like this:

List = [-550.0, -455.0, -355.0, -215.0, -195.0, 500.0, 645.0, 800.0, 975.0, 1265.0, 1370.0, 1615.0, 1615.0, 1615.0, 1615.0]