topic Re: Calculating a value from two feature class attribute fields in Python Questions

Calculating a value from two feature class attribute fields

GISAdministratorFranklin — Mon, 02 Aug 2021 19:35:58 GMT

I'm new to Python so thanks for your patience.

I'm working with two feature classes: Buildings and Parcels. What I'm trying to achieve is as follow:

Select a Parcel in ArcMap
The script will run the Select by Location tool to find the Building polygon within the Parcel polygon
The script will then divide the Building feature class's area field by the Parcel feature class's area field.
The output merely needs to be a numeric value.

Any help would be greatly appreciated!

Re: Calculating a value from two feature class attribute fields

DanPatterson — Mon, 02 Aug 2021 20:01:59 GMT

Did you look at

Spatial Join (Analysis)—ArcGIS Pro | Documentation

to get your started. It would enable you to sum the area of the buildings in the process.

The division can be done in a new field after the fact

Re: Calculating a value from two feature class attribute fields

Anonymous User — Mon, 02 Aug 2021 20:34:56 GMT

Are you creating a script tool for this?

You could try something like this to get you started, though you need to make sure that the selected parcel parameter type in your script tool is set to a feature layer (so only the selected parcel is used):

selectedParcel = arcpy.GetParameter(0) # I assume this is for a script tool buildingsFC = arcpy.GetParameterAsText(1) # path to buildings features # Get the selected parcels area parcelArea = arcpy.da.SearchCursor(selectedParcel, 'SHAPE@AREA').next() # intersect to find buildings selectedBuilding = arcpy.management.SelectLayerByLocation(buildingsFC, 'INTERSECT', selectedParcel, 'NEW_SELECTION') # iterate over selected buildings and calculate math stuff with arcpy.da.SearchCursor(selectedBuilding , 'SHAPE@AREA') as sCur: for row in sCur: print(f'area calc: {row[0]/ parcelArea}')

Re: Calculating a value from two feature class attribute fields

GISAdministratorFranklin — Mon, 02 Aug 2021 21:29:05 GMT

Thank you!