[arcpy] how to merge polygons into one multipart polygon

VincentLantaca

I am trying to merge polygons into one multi part polygon. I am trying to just append the polygon parts into one array and then creating a polygon from that array:

<SPAN class="keyword token">import</SPAN> arcpy

target_layer <SPAN class="operator token">=</SPAN> r<SPAN class="string token">'D:\DatabaseConnection\SCRAPWORK.sde\egdb.TEST.TEST_V'</SPAN>

where <SPAN class="operator token">=</SPAN> <SPAN class="string token">"OBJECTID IN (1601,1602,1603)"</SPAN>

arcpy<SPAN class="punctuation token">.</SPAN>MakeFeatureLayer_management<SPAN class="punctuation token">(</SPAN>target_layer<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">'test_layer'</SPAN><SPAN class="punctuation token">,</SPAN> where_clause<SPAN class="operator token">=</SPAN>where<SPAN class="punctuation token">)</SPAN>

polygons <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">]</SPAN>

arr <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">]</SPAN>
sr <SPAN class="operator token">=</SPAN> None

<SPAN class="keyword token">with</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>da<SPAN class="punctuation token">.</SPAN>SearchCursor<SPAN class="punctuation token">(</SPAN><SPAN class="string token">'test_layer'</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">'SHAPE@'</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
    <SPAN class="keyword token">for</SPAN> row <SPAN class="keyword token">in</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
        polygon <SPAN class="operator token">=</SPAN> row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN>

        <SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">'isMultipart: {}'</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>polygon<SPAN class="punctuation token">.</SPAN>isMultipart<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
        <SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">'partCount: {}'</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>polygon<SPAN class="punctuation token">.</SPAN>partCount<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
        sr <SPAN class="operator token">=</SPAN> polygon<SPAN class="punctuation token">.</SPAN>spatialReference
        <SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">''</SPAN><SPAN class="punctuation token">)</SPAN>

        <SPAN class="comment token"># add the polygon to an array</SPAN>
        arr<SPAN class="punctuation token">.</SPAN>append<SPAN class="punctuation token">(</SPAN>polygon<SPAN class="punctuation token">.</SPAN>getPart<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>

array <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>Array<SPAN class="punctuation token">(</SPAN>arr<SPAN class="punctuation token">)</SPAN>
multiPartPolygon <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>Polygon<SPAN class="punctuation token">(</SPAN>array<SPAN class="punctuation token">,</SPAN> sr<SPAN class="punctuation token">)</SPAN>

<SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">'MULTI PART POLYGON:'</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">'JSON:\n{}'</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>multiPartPolygon<SPAN class="punctuation token">.</SPAN>JSON<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">'isMultipart: {}'</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>multiPartPolygon<SPAN class="punctuation token">.</SPAN>isMultipart<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">'partCount: {}'</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>multiPartPolygon<SPAN class="punctuation token">.</SPAN>partCount<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">'spatialReference: {}'</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>multiPartPolygon<SPAN class="punctuation token">.</SPAN>spatialReference<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">'getPart: {}'</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>multiPartPolygon<SPAN class="punctuation token">.</SPAN>getPart<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

When I run the script, I am seeing that the three features that I am trying to merge are only 1 part polygons, but the polygon created has 0 part count, and no data in rings:

isMultipart: False
partCount: 1

isMultipart: False
partCount: 1

isMultipart: False
partCount: 1

MULTI PART POLYGON:
JSON:
{"rings":[],"spatialReference":{"wkid":4326,"latestWkid":4326}}
isMultipart: True
partCount: 0
spatialReference: <geoprocessing spatial reference object object at 0x1065FC80>
getPart: <geoprocessing array object object at 0x1065FC80><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

Can anyone point out what I am doing wrong? Any help is greatly appreciated!

DanPatterson

 arr <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">]</SPAN>
polys <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">]</SPAN>
sr <SPAN class="operator token">=</SPAN> <SPAN class="string token">"NAD 1983 CSRS MTM  9"</SPAN>
<SPAN class="keyword token">with</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>da<SPAN class="punctuation token">.</SPAN>SearchCursor<SPAN class="punctuation token">(</SPAN><SPAN class="string token">'test'</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">'SHAPE@'</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
    <SPAN class="keyword token">for</SPAN> row <SPAN class="keyword token">in</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
        polygon <SPAN class="operator token">=</SPAN> row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN>
        <SPAN class="keyword token">for</SPAN> cnt <SPAN class="keyword token">in</SPAN> range<SPAN class="punctuation token">(</SPAN>polygon<SPAN class="punctuation token">.</SPAN>partCount<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
            part <SPAN class="operator token">=</SPAN> polygon<SPAN class="punctuation token">.</SPAN>getPart<SPAN class="punctuation token">(</SPAN>cnt<SPAN class="punctuation token">)</SPAN>
            polys<SPAN class="punctuation token">.</SPAN>append<SPAN class="punctuation token">(</SPAN>part<SPAN class="punctuation token">)</SPAN>
            arr<SPAN class="punctuation token">.</SPAN>append<SPAN class="punctuation token">(</SPAN>part<SPAN class="punctuation token">)</SPAN>
a <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>Array<SPAN class="punctuation token">(</SPAN>arr<SPAN class="punctuation token">)</SPAN>

a
<SPAN class="operator token"><</SPAN>Array 
  <SPAN class="punctuation token">[</SPAN><SPAN class="operator token"><</SPAN>Array <SPAN class="punctuation token">[</SPAN><SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300009.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000001.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300000.0, 5000000.0, #, #)>,</SPAN>
           <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300002.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000008.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300008.0, 5000010.0, #, #)>,</SPAN>
           <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300010.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000010.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300010.0, 5000008.0, #, #)>,</SPAN>
           <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300009.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000001.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>,</SPAN>
           None<SPAN class="punctuation token">,</SPAN>
          <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300003.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000003.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300007.0, 5000003.0, #, #)>,</SPAN>
          <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300005.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000007.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300003.0, 5000003.0, #, #)>]>,</SPAN>
   <SPAN class="operator token"><</SPAN>Array <SPAN class="punctuation token">[</SPAN><SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300010.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000008.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300010.0, 5000010.0, #, #)>,</SPAN>
           <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300008.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000010.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300008.0, 5000011.0, #, #)>,</SPAN>
           <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300008.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000012.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300012.0, 5000012.0, #, #)>,</SPAN>
           <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300012.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000008.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300010.0, 5000008.0, #, #)>]>,</SPAN>
   <SPAN class="operator token"><</SPAN>Array <SPAN class="punctuation token">[</SPAN><SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300008.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000011.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300005.0, 5000010.0, #, #)>,</SPAN>
           <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300005.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000012.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300006.0, 5000012.0, #, #)>,</SPAN>
           <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300008.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000012.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300008.0, 5000011.0, #, #)>]>,</SPAN>
   <SPAN class="operator token"><</SPAN>Array <SPAN class="punctuation token">[</SPAN><SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300006.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000012.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300005.0, 5000012.0, #, #)>,</SPAN>
           <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300005.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000015.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>, <Point (300007.0, 5000014.0, #, #)>,</SPAN>
           <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300006.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000012.0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>]>]></SPAN>
<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

Before and after.  polygon with hole and 3 separate polygons.

The output (green)

p0 <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>Polygon<SPAN class="punctuation token">(</SPAN>a<SPAN class="punctuation token">)</SPAN>

p0<SPAN class="punctuation token">.</SPAN>partCount

p0<SPAN class="punctuation token">.</SPAN>isMultipart
<SPAN class="token boolean">True</SPAN>‍‍‍‍‍‍

p0<SPAN class="punctuation token">.</SPAN>getPart<SPAN class="punctuation token">(</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="operator token"><</SPAN>Array <SPAN class="punctuation token">[</SPAN><SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300006.0001220703</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000012.00012207</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>,</SPAN>
        <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300008.0001220703</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000012.00012207</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>,</SPAN>
        <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300012.0001220703</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000012.00012207</SPAN><SPAN class="punctuation token">,</SPAN>
        <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300006.0001220703</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000012.00012207</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>,</SPAN>
        None<SPAN class="punctuation token">,</SPAN>
        <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300003.0001220703</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000003.00012207</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>,</SPAN>
        <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300007.0001220703</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000003.00012207</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>,</SPAN>
        <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300005.0001220703</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000007.00012207</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>,</SPAN>
        <SPAN class="operator token"><</SPAN>Point <SPAN class="punctuation token">(</SPAN><SPAN class="number token">300003.0001220703</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5000003.00012207</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="comment token">#, #)>]></SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

 

Unexpected Result!!!!

Not at all, since you can't create multiparts that are disjoint if they share an edge, so the polygon resultant is indeed a multipart shape since it contains a hole, but the perimeter of the green output is the result of the dissolved boundaries from the input singlepart polygons.