topic Re: UdateCursor with Select By Location in Python Questions

UdateCursor with Select By Location

2Quiker — Sat, 11 Dec 2021 21:57:26 GMT

I am trying to do a select by location and then update the selected features, seems easy enough but i am see to get it figured out. Basically i want to update only the parcels that are within the City limits layer and update the 4 fields. I have tried different variations but i can't seem to get to work. I don't get any errors and also doesn't stop. I would appreciate any help.

Here is what i have.

import arcpy
from datetime import datetime as d
startTime = d.now()
start_time = time.time()

arcpy.env.overwriteOutput = True
arcpy.env.workspace = "C:/Temp/blah.gdb"

fc1 = "C:/Temp/blah.gdb/Parcels"

CITY = "C:/Temp/blah.gdb/City_Limits"

with arcpy.da.UpdateCursor(fc1, ['field1','field2','field3', 'field4']) as cursor:
    for row in cursor:
        #Select all parcels within the city limits layer
        arcpy.SelectLayerByLocation_management(fc1,"HAVE_THEIR_CENTER_IN", CITY)
        result = arcpy.GetCount_management(fc1)
        row [0] =  "IN CITY"
        row [1] =  "IN CITY"
        row [2] =  "IN CITY"
        row [3] =  "IN CITY"
        cursor.updateRow(row)
    del row, cursor
    
print('Done')
try:
    print ('(Elapsed time: ' + str(d.now() - startTime)[:-3] + ')')

except Exception as e:
    # If an error occurred, print line number and error message
    import traceback, sys
    tb = sys.exc_info()[2]
    print ("Line %i" % tb.tb_lineno)
    print (e.message)
‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: UdateCursor with Select By Location

DanPatterson_Retired — Wed, 11 Dec 2019 20:09:32 GMT

I don't see you using any 'layers' (aka, lyrx files) but featureclasses.

see code examples in

Make Feature Layer—Data Management toolbox | ArcGIS Desktop

Select Layer By Location—Data Management toolbox | ArcGIS Desktop

Re: UdateCursor with Select By Location

2Quiker — Sat, 11 Dec 2021 21:57:29 GMT

I tried the following nothing happens, no error and the fields don't get updated.

import arcpy
from datetime import datetime as d
startTime = d.now()
start_time = time.time()

arcpy.env.overwriteOutput = True
arcpy.env.workspace = "C:/Temp/blah.gdb"

fc1 = "C:/Temp/blah.gdb/Parcels"
arcpy.MakeFeatureLayer_management(fc1, "fc1tLyr")

CITY = "C:/Temp/blah.gdb/City_Limits"
arcpy.MakeFeatureLayer_management(CITY, "CityLyr")

with arcpy.da.UpdateCursor(fc1, ['field1','field2','field3', 'field4']) as cursor:
    for row in cursor:
        #Select all parcels within the city limits layer
        arcpy.SelectLayerByLocation_management("fc1tLyr","HAVE_THEIR_CENTER_IN", "CityLyr")
        result = arcpy.GetCount_management("fc1tLyr")
        row [0] =  "IN CITY"
        row [1] =  "IN CITY"
        row [2] =  "IN CITY"
        row [3] =  "IN CITY"
        cursor.updateRow(row)
    del row, cursor
    
print('Done')
try:
    print ('(Elapsed time: ' + str(d.now() - startTime)[:-3] + ')')

except Exception as e:
    # If an error occurred, print line number and error message
    import traceback, sys
    tb = sys.exc_info()[2]
    print ("Line %i" % tb.tb_lineno)
    print (e.message)‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: UdateCursor with Select By Location

JoeBorgione — Wed, 11 Dec 2019 23:22:37 GMT

Maybe you need to open an edit session? Editor—Help | ArcGIS Desktop

Re: UdateCursor with Select By Location

2Quiker — Wed, 11 Dec 2019 23:29:15 GMT

The data is in file database i didn't think i need to start an edit session.

Re: UdateCursor with Select By Location

JoeBorgione — Wed, 11 Dec 2019 23:43:44 GMT

Yeah, typically not....

Re: UdateCursor with Select By Location

DanPatterson_Retired — Wed, 11 Dec 2019 23:48:42 GMT

throw in a print statement to see how many were selected

Re: UdateCursor with Select By Location

JoeBorgione — Wed, 11 Dec 2019 23:57:33 GMT

But if none are actually selected, would all get updated?

Re: UdateCursor with Select By Location

DanPatterson_Retired — Thu, 12 Dec 2019 01:19:15 GMT

actually, I am not even sure why the selectbylocation is within the loop in the first place

and

Editor—Data Access module | ArcGIS Desktop

you may be right about the edit session since Pro ISN'T open (see the code samples at the end)

I suspect 1 selectbylocation with the featurelayer, then the edit session, then the cursor stuff with lots of print statements thrown in to see w.t.h. is going on

Re: UdateCursor with Select By Location

Anonymous User — Sat, 11 Dec 2021 21:57:31 GMT

Hi 2 Quicker (and not Dan ) <edited>

Nice script, a couple of things that should get it working:

move the selection outside of the "with" statement
you were not using the "result" of the count in this snippet, so i included some more print statements to give more feedback
the update cursor now runs on the selection rather than the full data set

if this doesn't work then i would suggest

adding in a unique identifier if one doesn't already exist
building a list/set from the selection
iterating over fc1 and updating the fields "if <uniqueID> in <list>"

If you like i can do up a skeleton of this option as well.

Hope this helps and good luck

Michael

import arcpy
from datetime import datetime as d

startTime = d.now()
start_time = time.time()

arcpy.env.overwriteOutput = True
arcpy.env.workspace = "C:/Temp/blah.gdb"

fc1 = "C:/Temp/blah.gdb/Parcels"

CITY = "C:/Temp/blah.gdb/City_Limits"

selection = arcpy.SelectLayerByLocation_management(fc1, "HAVE_THEIR_CENTER_IN", CITY)
numberoffeaturesfc1 = arcpy.GetCount_management(fc1)
result = arcpy.GetCount_management(selection)
count = 0

def findwhatsincity():
    global count
    with arcpy.da.UpdateCursor(selection, ['field1', 'field2', 'field3', 'field4']) as cursor:
        for row in cursor:
            # Select all parcels within the city limits layer
            row[0] = "IN CITY"
            row[1] = "IN CITY"
            row[2] = "IN CITY"
            row[3] = "IN CITY"
            count += 1
            cursor.updateRow(row)
        del row, cursor
    
    print('Done')
try:
    print ('Starting Script @ ' + startTime)
    findwhatsincity()
    print ('Number of features in ' + str(fc1) + ": " + str(numberoffeaturesfc1))
    print ('Number of features in selection: ' + str(result))
    print ('Number of features processed: ' + str(count))
    print ('(Elapsed time: ' + str(d.now() - startTime)[:-3] + ')')

except Exception as e:
    # If an error occurred, print line number and error message
    import traceback, sys

    tb = sys.exc_info()[2]
    print ("Line %i" % tb.tb_lineno)
    print (e.message)‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: UdateCursor with Select By Location

DanPatterson_Retired — Thu, 12 Dec 2019 03:59:16 GMT

Not my script

Re: UdateCursor with Select By Location

Anonymous User — Thu, 12 Dec 2019 04:02:37 GMT

Whoops
Sorry Dan and 2 Quicker

Re: UdateCursor with Select By Location

JoeBorgione — Thu, 12 Dec 2019 11:32:00 GMT

Just curious: Why declare count outside the def, and then make it global inside the def?

Re: UdateCursor with Select By Location

2Quiker — Sat, 11 Dec 2021 21:57:34 GMT

Thanks everyone that replied. I was able to come with the following code that works for me.

fyi, Michael Boyce your code did work by the way.

import arcpy
from datetime import datetime as d
startTime = d.now()
start_time = time.time()

arcpy.env.overwriteOutput = True
arcpy.env.workspace = "C:/Temp/blah.gdb"

fc1 = "C:/Temp/blah.gdb/Parcels"
arcpy.MakeFeatureLayer_management(fc1, "fc1Lyr")

CITY = "C:/Temp/blah.gdb/City_Limits"
arcpy.MakeFeatureLayer_management(CITY, "CityLyr")

with arcpy.da.SearchCursor("CityLyr", ["SHAPE@"]) as cursor:
    for row in cursor:
        #SELECT PROPERTIES BY CITYLIMITS
        selection = arcpy.SelectLayerByLocation_management("fc1Lyr","HAVE_THEIR_CENTER_IN", "CityLyr")
        result = int(arcpy.GetCount_management("fc1Lyr").getOutput(0)) 
        with arcpy.da.UpdateCursor(selection, ['field1','field2','field3', 'field4']) as cursor:
            for row in cursor:
                # Select all parcels within the city limits layer
                row[0] = "IN CITY"
                row[1] = "IN CITY"
                row[2] = "IN CITY"
                row[3] = "IN CITY"
                cursor.updateRow(row)
            del row, cursor

try:
    print ('(Elapsed time: ' + str(d.now() - startTime)[:-3] + ')')
    print ('Number of features processed: ' + str(result))

except Exception as e:
    # If an error occurred, print line number and error message
    import traceback, sys
    tb = sys.exc_info()[2]
    print ("Line %i" % tb.tb_lineno)
    print (e.message)‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: UdateCursor with Select By Location

Anonymous User — Thu, 12 Dec 2019 21:20:55 GMT

Umm, no reason. Since i was coding on the fly i didn't really think about it. By rights you are correct and that it should be inside the def to make the code cleaner. Then it would not require the global call.

Re: UdateCursor with Select By Location

Anonymous User — Thu, 12 Dec 2019 21:38:10 GMT

Very nice

Good to see you got a solution

Just a pointer to make your code more error proof:
At the moment the only things in the try/except statement are the print statements.

This means that an exception will only be called if something goes wrong with the print calls, but an exception will not be handled in any of the calls above.
Either move the try to the top, around line 14 or define a function and place everything in it then call the function inside the try statement at the bottom.

This way if something goes wrong you will be able to debug a whole lot better.

Happy coding

Re: UdateCursor with Select By Location

JoeBorgione — Thu, 12 Dec 2019 21:56:40 GMT

Okay cool... I avoid global variables and it just kind of jumped out at me!

Re: UdateCursor with Select By Location

Anonymous User — Thu, 12 Dec 2019 22:07:31 GMT

I usually do as well, but i just finished scripting a fairly interesting project where i had to pass variables between three different scripts for threading. So i guess that i had globals on the brain.