I'm new to python and trying to figure out if this is possible. I have a measured layer with segments in it. I want to add a begin segment and end segment field. The layer has the following fields. Corridor, Ref Marker, shape length, beg_seg and end_seg. I would like to populate the begin seg and end seg from the shape_length field and accumulate them. So the mile post zero beg_seg would start at zero and the end_seg field would be the length of the zero segment. Then mile post 1 beg_seg would be the value of the end_seg of mile post one. The end_seg for mile post one would be the value of mile post 0 length plus the length of mile post one. this would continue till the last mile post. I have attached a image of the table that I manually entered the values for. I was hoping to create a python script to perform this as I have a ton of corridors with a ton of records. One other piece of information is some of the corridors may be missing mile posts.