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I want to duplicate a polygon feature class and offset all of the polygons by about 10 feet in both the x and y directions. I asked if there was any way to do this last week, and I was informed that I would most likely need to make my own python script using arcpy. I made my own script using arcpy, but it isn't working:

import arcpy
from arcpy import env
import os

env.overwriteOutput = True

# Get arguments: 
#   Input polygon feature class
#   Output polygon feature class
#
inputFeatureClass = arcpy.GetParameterAsText(0)
outputFeatureClass = arcpy.GetParameterAsText(1)
xShift = arcpy.GetParameterAsText(2)
yShift = arcpy.GetParameterAsText(3)

shapeName = arcpy.Describe(inputFeatureClass).shapeFieldName

# Create the output feature class with the same fields and spatial reference as the input feature class
arcpy.CreateFeatureclass_management(os.path.dirname(outputFeatureClass), os.path.basename(outputFeatureClass), "POLYGON", inputFeatureClass, "", "", inputFeatureClass)

# Create a search cursor to iterate through each row of the input feature class
inrows = arcpy.SearchCursor(inputFeatureClass)
# Create an insert cursor to insert rows into the output feature class
outrows = arcpy.InsertCursor(outputFeatureClass)

# Create empty Point and Array objects
pntArray = arcpy.Array()
partArray = arcpy.Array()

# Loop through each row/feature
for row in inrows:
    # Create the geometry object
    feature = row.getValue(shapeName)

    partnum = 0

    # Count the total number of points in the current multipart feature
    partcount = feature.partCount


    while partnum < partcount:
        part = feature.getPart(partnum)
        pnt = part.next()
        pntcount = 0

        # Enter while loop for each vertex
        #
        while pnt:

            pnt = part.next()
            shiftedPoint = arcpy.Point()
            try:
                shiftedPoint.ID = pnt.ID
                shiftedPoint.X = pnt.X + float(xShift)
                shiftedPoint.Y = pnt.Y + float(yShift)
            except AttributeError:
                continue
            #shiftedPoint = arcpy.Point(float(pnt.X) + float(xShift), float(pnt.Y) + float(yShift))
            pntArray.add(shiftedPoint)
            pntcount += 1

            # If pnt is null, either the part is finished or there is an 
            #   interior ring
            #
            if not pnt: 
                pnt = part.next()
                if pnt:
                    arcpy.AddMessage("Interior Ring:")
        # Create a polygon using the array of points
        polygon = arcpy.Polygon(pntArray)

        # Empty the array for the next run through the loop
        pntArray.removeAll()

        # Add the polygons (or 'parts') to an array. This is necessary for multipart features, or those with holes cut in them
        partArray.add(polygon)
        arcpy.AddMessage("Added a polygon to the partArray!")
        partnum += 1

    # Create a new row object that will be inserted into the ouput feature class. Set newRow = row so that it has the same attributes
    # Set newRow.shape = partArray so that the only thing different about this new feature is that its geometry is different (shifted)
    newRow = row
    newRow.shape = partArray

    outrows.insertRow(newRow)

    # Empy the array for the next run through the loop
    partArray.removeAll()

del inrows, outrows

I keep getting this error on line 70

<type 'exceptions.ValueError'>: Array: Add input not point nor array object

I can't figure out why it's giving me this error, since I defined the input as an array.

If anyone knows why I'm getting this error, or if there's anything else wrong with my code, I would greatly appreciate it.

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1 Answer 1

up vote 12 down vote accepted

Instead of creating and trying to add a polygon to your array, add your array of points to the array of parts. Change this:

polygon = arcpy.Polygon(pntArray)
pntArray.removeAll()
partArray.add(polygon)

To this:

partArray.add(pntArray)
pntArray.removeAll()

Also, there's a problem with your code that tries to insert the row. You need to use your insert cursor to create a new row and insert it. Starting at line 77 in your original code sample:

newRow = outrows.newRow()
newRow.shape = partArray
outrows.insertRow(newRow)

Edit: You should also move the "pnt = part.next()" in your inner while loop to below your try/except block so you don't skip any points and so that the if block that tests for interior rings runs. As is, the code in your post will not pick up interior rings. Here's the whole thing after all the modifications I've described:

import arcpy
from arcpy import env
import os

env.overwriteOutput = True

# Get arguments: 
#   Input polygon feature class
#   Output polygon feature class
#
inputFeatureClass = arcpy.GetParameterAsText(0)
outputFeatureClass = arcpy.GetParameterAsText(1)
xShift = arcpy.GetParameterAsText(2)
yShift = arcpy.GetParameterAsText(3)
print '\nparams: ', inputFeatureClass, outputFeatureClass, xShift, yShift, '\n'

shapeName = arcpy.Describe(inputFeatureClass).shapeFieldName

# Create the output feature class with the same fields and spatial reference as the input feature class
if arcpy.Exists(outputFeatureClass):
    arcpy.Delete_management(outputFeatureClass)
arcpy.CreateFeatureclass_management(os.path.dirname(outputFeatureClass), os.path.basename(outputFeatureClass), "POLYGON", inputFeatureClass, "", "", inputFeatureClass)

# Create a search cursor to iterate through each row of the input feature class
inrows = arcpy.SearchCursor(inputFeatureClass)
# Create an insert cursor to insert rows into the output feature class
outrows = arcpy.InsertCursor(outputFeatureClass)

# Create empty Point and Array objects
pntArray = arcpy.Array()
partArray = arcpy.Array()

# Loop through each row/feature
for row in inrows:
    # Create the geometry object
    feature = row.getValue(shapeName)
    partnum = 0
    # Count the total number of points in the current multipart feature
    partcount = feature.partCount
    print 'num parts: ', partcount
    while partnum < partcount:
        part = feature.getPart(partnum)
        pnt = part.next()
        print 'outer while'
        pntcount = 0
        # Enter while loop for each vertex
        #
        while pnt:
            shiftedPoint = arcpy.Point()
            try:
                shiftedPoint.ID = pnt.ID
                shiftedPoint.X = pnt.X + float(xShift)
                shiftedPoint.Y = pnt.Y + float(yShift)
            except AttributeError:
                continue
            pntArray.add(shiftedPoint)
            pntcount += 1
            pnt = part.next()
            print 'pntcount: ', pntcount
            # If pnt is null, either the part is finished or there is an 
            #   interior ring
            if pnt is None: 
                pnt = part.next()
                if pnt:
                    arcpy.AddMessage("Interior Ring:")
        partArray.add(pntArray)
        pntArray.removeAll()
        arcpy.AddMessage("Added a polygon to the partArray!")
        partnum += 1
    # Create a new row object that will be inserted into the ouput feature class. Set newRow = row so that it has the same attributes
    # Set newRow.shape = partArray so that the only thing different about this new feature is that its geometry is different (shifted)
    newRow = outrows.newRow()
    newRow.shape = partArray
    outrows.insertRow(newRow)
    # Empy the array for the next run through the loop
    partArray.removeAll()
del inrows, outrows
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I just discovered that the script shifts everything perfectly, except for features that have 2 or more interior rings. It will leave lines connected, and distort the polygon. Do you know how to account for this? –  Tanner Dec 12 '10 at 19:56
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