Comparing geometries using Search Cursors

Question

I'm working on a little arcpy script to compare the geometry of features (linked by a matching ID field

I've got a couple of search cursors populating dictionaries for the two feature classes which I then am trying to compare to find where features (that should be identical shapes) don't match.

I have run into a snag in my concept though in that the output from SHAPE@ is returning False when I compare the features I know are identical (should return True).

import arcpy
fields = ['LineID', 'SHAPE@']
x = 'Line1' # Feature Class #1
y = 'Line2' # Feature Class #2
xDict = dict()
yDict = dict()
with arcpy.da.SearchCursor(x, fields) as cursor:
    for row in cursor:
        xDict[row[0]] = row[1]
with arcpy.da.SearchCursor(y, fields) as cursor:
    for row in cursor:
        yDict[row[0]] = row[1]

When I test I get False returned:

xDict[1] == yDict[1]
> False

This returns False even though I know that record #1 is identical in both feature classes.

Is there another way I can use my search cursors to compare the shape of the two features? I know there are .WKB, .WKT, .JSON options for Shape - are these valid options for a comparison? My brief testing suggests they are, but I'm unsure whether there are occasions where they would also return False.

xDict[1].WKB == yDict[1].WKB
> True

xDict[1].equals(yDict[1]) # Should be True
> True
xDict[2].equals(yDict[2]) # Should be False
> True
xDict[4].equals(yDict[4]) # Should be False
> False

Answer 1

I still think there should be a better way to do this, but this is what I've come up with, using SHAPE@WKB for the comparison of the shapes (matched on FeatID) in my two feature classes.

Here are my shapes - The arrows point at the start location:

And my script, including a description of what should be returned for each shape:

import arcpy

x = r'D:\temp\SE\CompareShapes\Data.gdb\TestPoly1'
y = r'D:\temp\SE\CompareShapes\Data.gdb\TestPoly2'

fields = ['FeatID', 'SHAPE@']
xDict = dict()
yDict = dict()
testDict = {
            1 : 'True - Identical',
            2 : 'False - Same shape, different start point',
            3 : 'True - Identical',
            4 : 'False - Same shape, different start point',
            5 : 'True - Identical',
            6 : 'False - Same shape, different start point',
            7 : 'False - Same shape, extra vertex',
            8 : 'False - Shape shape, different position (rotated)',
            9 : 'True - Identical'
           }

with arcpy.da.SearchCursor(x, fields) as cursor:
    for row in cursor:
        xDict[row[0]] = row[1]

with arcpy.da.SearchCursor(y, fields) as cursor:
    for row in cursor:
        yDict[row[0]] = row[1]

# Only 1, 3, 5, 9 are identical and should return True - rest should return False
for xx in xDict:
    print "Feature:        {}".format(xx) # FeatID of feature
    print "Expected:       {}".format(testDict[xx]) # Description of expected result
    print "x.equals(y):    {}".format(xDict[xx].equals(yDict[xx])) # Does the SHAPE@ equal SHAPE@?
    print "x.WKB == y.WKB: {}".format(xDict[xx].WKB == yDict[xx].WKB) # Does the WKB equal for each SHAPE@?

This returns the following output, which shows that x.equals(y) doesn't always return the required/expected value, and x.WKB == y.WKB seems to consistently return the expected value:

Feature:        1  
Expected:       True - Identical  
x.equals(y):    True  
x.WKB == y.WKB: True  
Feature:        2  
Expected:       False - Same shape, different start point  
x.equals(y):    True  
x.WKB == y.WKB: False  
Feature:        3
Expected:       True - Identical
x.equals(y):    True
x.WKB == y.WKB: True
Feature:        4
Expected:       False - Same shape, different start point
x.equals(y):    True
x.WKB == y.WKB: False
Feature:        5
Expected:       True - Identical
x.equals(y):    True
x.WKB == y.WKB: True
Feature:        6
Expected:       False - Same shape, different start point
x.equals(y):    True
x.WKB == y.WKB: False
Feature:        7
Expected:       False - Same shape, extra vertex
x.equals(y):    True
x.WKB == y.WKB: False
Feature:        8
Expected:       False - Shape shape, different position (rotated)
x.equals(y):    False
x.WKB == y.WKB: False
Feature:        9
Expected:       True - Identical
x.equals(y):    True
x.WKB == y.WKB: True