sort pointcloud by x,y values

hey everyone,

i am trying to sort a point-cloud by its x,y values. I have a parametric cloud of points from 3 data strings flattened into a point param -> to be able to connect these with specific lines i need to sort these by its x and y values to be able to use the shift list function. with the sort list function i am able to sort this list by either x or y values, but i am not able to sort them by both. the new list should start with the smallest x and y value, then list all points with the same y value and rising x values, then go to the next y value and list the points with rising x values and so on... is there a solution to this?

a second problem.. is it possible to devide a string into separate data strings by y value? starting with a point cloud again i would like to seperate it in strings of points with the same y value and varying x values. if the cloud is generated parametric, the number of strings needs to be variable as well... solutions?

i hope someone can help, thanks already..
Felix