topic Re: python - merge polys in arcmap in Python Questions

python - merge polys in arcmap

GailMorrison — Wed, 18 Sep 2019 19:38:23 GMT

Greetings! I have feature data sets that have 1+ polys. The ArcMap merge tool works great. How do I script this type of processing using Python?

Thx! Gail

Re: python - merge polys in arcmap

Jeremy_Moore — Thu, 19 Sep 2019 00:14:19 GMT

Take a look at arcpy.Merge_management() which will combine your FeatureClasses into one FeatureClass as a single polygon

Merge—Data Management toolbox | ArcGIS Desktop

You could also use arcpy.Append_management() however this will combine your FeatureClasses into a single FeatureClass without merging into a single polygon.

Append—Data Management toolbox | ArcGIS Desktop

Then if you needed to combine features in a FeatureClass into a single polygon you want to use arcpy.Dissolve_management()

Dissolve—Data Management toolbox | ArcGIS Desktop

3 different tools that do essentially the same thing visually on different data types.

If you need help on how to use these tools please don't hesitate to ask. There are no dumb question.

Hope this helps

Re: python - merge polys in arcmap

GailMorrison — Thu, 19 Sep 2019 17:36:12 GMT

I don't think I asked the question correctly. The above answer is for merging datasets. I need a script to merge polygons within each dataset.

Re: python - merge polys in arcmap

Jeremy_Moore — Thu, 19 Sep 2019 17:48:33 GMT

Just to make sure we are on the same page:

When you say dataset are you referring to a feature dataset, which is a collection of related feature classes that share a common coordinate system? Or are you referring to polygon features in a single feature class?

I apologize if I'm being dense

Re: python - merge polys in arcmap

GailMorrison — Thu, 19 Sep 2019 17:51:51 GMT

Oh, you are not being dense. I am being sloppy with my verbaige. I am referring to polygon features in a single feature class

Re: python - merge polys in arcmap

Jeremy_Moore — Thu, 19 Sep 2019 18:27:47 GMT

Alright, so polygon features in a feature class. You would want to use arcpy.Dissolve_management()

Dissolve—Data Management toolbox | ArcGIS Desktop

If you need a code example let me know.

Re: python - merge polys in arcmap

GailMorrison — Thu, 19 Sep 2019 18:46:22 GMT

The catch is that I need to keep all the fields in the attribute table. Unless I calculate all the field values to be the same, this won't work for what I need. Example: Fields = sqmi, sqft, sqkm, name. If I dissolve on Name, the other 3 fields drop out of the feature class.

Re: python - merge polys in arcmap

Jeremy_Moore — Sun, 12 Dec 2021 04:42:43 GMT

Sorry for the delay in getting back to you. I have been playing around with some other tools to try to find a solution for you. Once the geometry has been combined and the attributes limited down to a single row, do you need any information in that row?

I have been able to preserve your fields. Try this script and see how it works for you

import arcpy

inFeatureClass = r"C:\Users\JohnDoe\Documents\ArcGIS\Projects\General\General.gdb\dissolve_polygons"
outFeatureClass = r"C:\Users\JohnDoe\Documents\ArcGIS\Projects\General\General.gdb\dissolve_test"
listFields = arcpy.ListFields(inFeatureClass)

print("Dissolving polys")
arcpy.Dissolve_management(inFeatureClass, outFeatureClass)

print("Adding Fields")
for addField in listFields:
    try:
        arcpy.AddField_management(outFeatureClass, addField.name, addField.type, "", "", addField.length, "", "", "")
    except:
        continue‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍