ArcGIS method to partially erase or clip thousands of related polygons

Question

I am looking for a way to remove part of a polygon that overlaps with a polygon in another layer.
Specifically I have two datasets, one is a set of square polygons and the other is a set of convex hull polygons which originates from each square polygon. I now need to remove from each convex hull that part which intersects with the square it originates from. The part of the convex hull not within the originating square should remain intact as it will be dealt with in a subsequent process.

The square polygons, each is used to create a convex hull. The convex hulls. The only part to erase is the circular area within each square. This is my result from Model Builder. Correctly removed part within the square but only one, I need over 50,000 removed. Any help improving this Model or do I need a different approach?

Answer 1

Perhaps run this calculator expression on field Shape of your target:

def getSegment(ID):
 f = arcpy.AddFieldDelimiters("HULLS","LABEL")
 q="%s='%s'" %(f,ID)
 with arcpy.da.SearchCursor("HULLS", 'Shape@',q) as cursor:
  for row in cursor:  pair=row[0]
 with arcpy.da.SearchCursor("TARGET", 'Shape@',q) as cursor:
  for row in cursor:  shp=row[0]
 m=shp.difference (pair)
 return m
#---------------
getSegment( !Label! )

BEFORE:

AFTER:

Python expression above assumes:

• your target layer is stored as shapefile and named "TARGET" in the table of current mxd.
• eraser layer stored as shapefile and named "HULLS" in the table of current mxd.
• Common field in both layers is text field called "Label". If this not a case create such field in both and populate them from existing common fields.

NOTE: script modifies shapes in existing target layer, so create backup copy first.

First learn how to use advanced field calculator in arcgis.