Why does ArcMap edit session show different vertex count on feature than arcpy/ ArcToolbox

Question

I am looking at features in an ArcSDE geodatabase via ArcMap. The feature shows to have four vertices by viewing the vertices in the map and by looking at the sketch properties.

However if I run a feature vertex to point tool i get 5 vertices. If I get an arcpy.SearchCursor row object and do row.pointCount I get 5 vertices reported.

I even exported the feature class out to a shapefile and got the same results.

Whats going on here? Thanks.

Answer 1

It sounds like you are working with polygons. I created a 4-corner polygon in a FGDB, and when I look at it in the editor, it does have 4 vertices:

However, when I run the following script on it, you can see it does indeed have 5 vertices (as it should), where the first and last are the same in order to close the polygon:

import arcpy

infc = "NumberOfVertices"
desc = arcpy.Describe(infc)
shapefieldname = desc.ShapeFieldName
rows = arcpy.SearchCursor(infc)
for row in rows:
    feat = row.getValue(shapefieldname)
    print "\tFeature %i:" % row.getValue(desc.OIDFieldName)
    partnum = 0
    for part in feat:
        parts = []
        print "Part %i:" % partnum
        for pnt in feat.getPart(partnum):
            if pnt:
                parts.append([pnt.X, pnt.Y])
            else:
                parts.append(" ")
        partnum += 1 
    print parts  

Part 0:
[[414609.77850000001, 3711987.8151999991], [421594.30240000039, 3711987.8151999991], [421926.89879999962, 3700346.9419999998], [414277.18209999986, 3701178.4329000004], [414609.77850000001, 3711987.8151999991]]

>>> len(parts)
5
>>>