I was creating polygons via a python script when I noticed that rows in the table were being inserted but some of the actual polygon shapes were missing. I had just rewritten this 9.3.1 python script to work with arcpy and version 10+. I ran the 9.3.1 script and all polygon shapes were complete.

I opened ArcMap 10.2.1 and manually entered the new code into the Python window:

>>> import arcpy

>>> array = arcpy.Array()

>>> array.add(arcpy.Point(-92.09936200, 46.73024000))

>>> array.add(arcpy.Point(-92.09936200, 46.73137900))

>>> array.add(arcpy.Point(-92.09782100, 46.73137900))

>>> array.add(arcpy.Point(-92.09782100, 46.73024000))

>>> array.add(arcpy.Point(-92.09936200, 46.73024000))

>>> cur = arcpy.da.InsertCursor("onecall_poly", ["SHAPE@"])

>>> cur.insertRow([arcpy.Polygon(array)])

0L

>>> array.removeAll()

>>> del array, cur

This created a row in the feature class table but did not create a polygon.

I then typed the following code into the Python window:

>>> import arcgisscripting

>>> gp = arcgisscripting.create(9.3)

>>> array = gp.createobject("Array")

>>> pnt = gp.createobject("Point")

>>> pnt.x = -92.09936200

>>> pnt.y = 46.73024000

>>> array.add(pnt)

>>> pnt.x = -92.09936200

>>> pnt.y = 46.73137900

>>> array.add(pnt)

>>> pnt.x = -92.09782100

>>> pnt.y = 46.73137900

>>> array.add(pnt)

>>> pnt.x = -92.09782100

>>> pnt.y = 46.73024000

>>> array.add(pnt)

>>> pnt.x = -92.09936200

>>> pnt.y = 46.73024000

>>> array.add(pnt)

>>> cur = gp.insertcursor("onecall_poly")

>>> feat = cur.newrow()

>>> feat.shape = array

>>> cur.insertrow(feat)

>>> array.removeall()

>>> del cur, array

This created the table record and the polygon feature.

Am I doing something wrong? Why doesn't the new code work? In the help it says that "All geometries are validated before they are written to a feature class." What does 0L mean after the insertRow command in my first example?

Building off Ian's answer, and for some reason remembering what I think were Dan Patterson's wise words, "You must set a spatial reference when creating geometries", behold: