Select the outer user set number of points from a curve or surface, optionally the inverse

SelOuterPoints.py

import Rhino
import rhinoscriptsyntax as rs
import scriptcontext as sc

def SelOuterPoints():
    ids = None
    while True:
        maxPts = 1
        if sc.sticky.has_key('MAX_OUTER_PTS'):
            maxPts = sc.sticky['MAX_OUTER_PTS']
            
        flip = False
        if sc.sticky.has_key('FLIP_OUTER_PTS'):
            flip = sc.sticky['FLIP_OUTER_PTS']
            
        go = Rhino.Input.Custom.GetObject()
        go.SetCommandPrompt("Select open curves and surfaces.")
        
        go.GeometryFilter = Rhino.DocObjects.ObjectType.Curve|Rhino.DocObjects.ObjectType.Surface
        go.GeometryAttributeFilter = Rhino.Input.Custom.GeometryAttributeFilter.OpenSurface |Rhino.Input.Custom.GeometryAttributeFilter.OpenCurve
        
        go.AcceptNumber(True, False)
        
        opInvert = Rhino.Input.Custom.OptionToggle(flip, 'No', 'Yes')
        go.AddOptionToggle("InvertPoints", opInvert)
        
        opMax = Rhino.Input.Custom.OptionInteger(maxPts, True,1)
        go.AddOptionInteger("NumberOfPoints", opMax)
        
        rc = go.GetMultiple(1,0)
        
        if go.CommandResult()!=Rhino.Commands.Result.Success:
            return go.CommandResult()
            
        if rc==Rhino.Input.GetResult.Number:
            num = go.Number()
            if num.is_integer:
                maxPts = int(num)
                sc.sticky['MAX_OUTER_PTS'] = maxPts
                continue
                
        if rc==Rhino.Input.GetResult.Option:
            maxPts = opMax.CurrentValue
            flip = opInvert.CurrentValue
            sc.sticky['FLIP_OUTER_PTS'] = flip
            sc.sticky['MAX_OUTER_PTS'] = maxPts
            continue
                
        if rc==Rhino.Input.GetResult.Object:
            ids = [go.Object(n).ObjectId for n in range(go.ObjectCount)]
            break
            
            
    if not ids: return

    if not maxPts: return
    sc.sticky['MAX_OUTER_PTS'] = maxPts
    
    SelThePoints(maxPts, ids, flip)
    
def SelThePoints(ptCount, ids, flip):

    rs.EnableRedraw(False)
    
    for id in ids:
        if rs.ObjectGripsSelected(id):
            rs.EnableObjectGrips(id, False)
        rs.EnableObjectGrips(id)
        selIdx = []
        if rs.IsCurve(id):
            
            count = rs.CurvePointCount(id)
            for i in range(0, ptCount):
                selIdx.append(i)
                selIdx.append((count -1)-i)
                     
        else:
            srf = rs.coercegeometry(id).Faces[0].UnderlyingSurface()
            pts = srf.Points
            count = rs.SurfacePointCount(id)
            max  = count[0] * count[1]
            
            # U
            if not srf.IsClosed(0):
                for n in range(0,count[1]):
                    selIdx.append (n)
                    for i in range(1, ptCount):
                        selIdx.append (n + (i*count[1]))
                
                for n in range(max-count[1], max):
                    selIdx.append( n)
                    for i in range(1, ptCount):
                        selIdx.append(n - (i*count[1]))
            #V
            if not srf.IsClosed(1):
                for n in range(0,count[0]):
                   idxNear = n*count[1]
                   idxFar  = idxNear + count[1]-1
                   
                   selIdx.append( idxNear )
                   selIdx.append(idxFar)
                   
                   for i in range(ptCount):
                       selIdx.append(idxNear + i)
                       selIdx.append(idxFar - i)
        if flip:
            for i in range(count[0] * count[1]):
                if i not in selIdx: rs.SelectObjectGrip(id, i)
        else:
            for i in selIdx:
                rs.SelectObjectGrip(id, i)

    rs.EnableRedraw(True)

            
if __name__ == '__main__': SelOuterPoints()