topic Re: Python and Relates in Python Questions

Python and Relates

CynthiaKozma — Thu, 30 Oct 2014 17:33:02 GMT

I am new to Python, so this may have a simple answer. This is something that I used to write in AML in 10 minutes. I want to relate a feature class to a table, select all records in the feature class - which would select related records in the table, do a switch selection on the table and create a new feature from the table. My script does what it is supposed to when I use a small sample set, but totally crashes ArcMap so that it closes completely about 1/4 of the way through the full (13,000) records. I believe it has something to do with the nested cursors that I have going. How can I keep it from crashing and closing and finish the script? Any help would be great! Or if there is an easier way to do a relate in python??

This is the piece where is does a "relate" and ArcMap closes..........

# Create a search cursor to loop through the building_pt_sewer table

arcpy.SelectLayerByAttribute_management("building_clip", "NEW_SELECTION", "OBJECTID > 0")

buildings = arcpy.SearchCursor("building_clip")

parc_field = "parcels_ASSESSOR_N_1"

for building in buildings:

#Get Parcel Number of building

building_ID = building.getValue(parc_field)

# Create search cursor for looping through the buildings

sewers = arcpy.SearchCursor(DestinationTable)

sewer_field = "parcel_id"

for sewer in sewers:

#Get parc of sewer

sewer_parc = sewer.getValue(sewer_field)

query = "parcel_id = " + "'%s'" %building_ID

print query

arcpy.SelectLayerByAttribute_management(DestinationTable, "ADD_TO_SELECTION", query)

# break

del buildings, sewers

Re: Python and Relates

JoshuaBixby — Thu, 30 Oct 2014 18:01:56 GMT

Are you using ArcGIS 10.1 or greater? If so, I encourage you to give the cursors in the arcpy data access (arcpy.da) module a try. The data access cursors are more robust and may not crash as easily.

Re: Python and Relates

CynthiaKozma — Thu, 30 Oct 2014 18:31:27 GMT

We do...we are running 10.2.1. I will check that out! Thank you!

Re: Python and Relates

JoshuaBixby — Thu, 30 Oct 2014 18:45:32 GMT

Also, there is some good information on this topic in StackExchange: How can I more efficiently select related records?

Re: Python and Relates

CynthiaKozma — Fri, 31 Oct 2014 23:22:51 GMT

That worked like a charm --- and was about 100x faster processing! Thank you!

Re: Python and Relates

JoshuaBixby — Sat, 01 Nov 2014 15:07:39 GMT

Glad it worked out for you. I used that same discussion last year to sort through a similar issue, figured it better to point you there than repeat it all here. Cheers.