topic Re: Creating Multipart Objects in ArcGIS Pro Questions

Creating Multipart Objects

JamesCarroll7 — Thu, 11 Dec 2025 15:17:45 GMT

Hi all,

I have a polyline shapefile layer in ArcGIS Pro which shows the road system of a proposed development. All of the roads are on this one layer, but I want to break it down into different selectable sectors for different parts of the development. I used the Multipart to Singlepart tool to break down the shapefile, but I can't find a tool to allow me to select certain polylines to group together (I essentially want to create the equivalent of a block in AutoCAD where all the roads in Sector 1 are grouped together, all the roads in Sector 2 are grouped together etc.). Is it possible to do this in GIS?

Re: Creating Multipart Objects

DanPatterson — Thu, 11 Dec 2025 15:29:17 GMT

not sure if you want the features to remain in the same layer or not. If you want separate layers for each grouping see

Split By Attributes (Analysis)—ArcGIS Pro | Documentation

or if you want to split by using another geometry layer Split (Analysis)—ArcGIS Pro | Documentation

The opposite of multipart to singlepart is

Dissolve (Data Management)—ArcGIS Pro | Documentation

Re: Creating Multipart Objects

DavidSolari — Thu, 11 Dec 2025 17:17:31 GMT

Like Dan said, Dissolve with the "sector" field should be enough. If you need a more specific workflow, here's an arcpy function that'll condense a bunch of geometries into one multipart:

import ujson def reduce_geoms(geoms: list[arcpy.Geometry]) -> arcpy.Geometry: iter_geom = iter(geoms) first = next(iter_geom) assert first.type != "point" retval = ujson.loads(first.JSON) has_curves = "curvePaths" in retval path_key = "curvePaths" if has_curves else "paths" for g in iter_geom: gson = ujson.loads(g.JSON) paths = None if "curvePaths" in gson: paths = gson["curvePaths"] if not has_curves: retval["curvePaths"] = retval["paths"] del retval["paths"] path_key = "curvePaths" else: paths = retval["paths"] retval[path_key].extend(paths) return arcpy.AsShape(retval, True)

Re: Creating Multipart Objects

JamesCarroll7 — Tue, 16 Dec 2025 09:18:29 GMT

Many thanks Dan, that worked a treat. I do need all of the multipart features to be in one layer, but I used the 'Merge' tool to do that once I had all the multipart features created.

Re: Creating Multipart Objects

JamesCarroll7 — Tue, 16 Dec 2025 09:18:52 GMT

Thanks for that David, very helpful, I appreciate it!