topic Re: I need help on the Update Cursor function in Python Questions

I need help on the Update Cursor function

OLANIYANOLAKUNLE — Thu, 23 Aug 2012 14:27:11 GMT

Im trying to update a field called "GENERATED" with an attribute called "GENERATED" every time i autogenerate a map, i constructed this script and it is not updating and i didnt see an error(s)

rows = arcpy.UpdateCursor("Parcels",'[OBJECTID] = "1"')
row = rows.next()
while row:
    row.setvalue(GENERATED, GENERATED)
    rows.updateRow(row)
    row = rows.next()

Please any suggestions. Im desperate. Thanks

Re: I need help on the Update Cursor function

ChristopherThompson — Thu, 23 Aug 2012 14:46:57 GMT

I suspect the naming is throwing it off, if GENERATED is the field name, it looks like you're trying to set the value equal to itself. Perhaps this will work:

row.setvalue(GENERATED, 'GENERATED')

That way the function can distinguish between a field and a value.
I've also had success with:

row.GENERATED = 'GENERATED'

Re: I need help on the Update Cursor function

MathewCoyle — Sat, 11 Dec 2021 18:35:05 GMT

Try this.


rows = arcpy.UpdateCursor("Parcels", "[OBJECTID] = 1")

for row in rows:
    row.setValue("GENERATED", "GENERATED")
    rows.updateRow(row)

You shouldn't have quotes around your objectid query selection. Also not sure if you have assigned GENERATED as a variable, but if you haven't you will need quotes. Also make sure you are using the right field delimiters for your OBJECTID field.

Re: I need help on the Update Cursor function

markdenil — Sat, 11 Dec 2021 18:35:08 GMT

First off, with an arcpy cursor you don't use .next() in a while loop,
you simply itterate the cursor:

for row in rows:
    ...do stuff

Your query string looks problematic
'[OBJECTID] = "1"'
should be something like
'"OBJECTID" = \'1\''
using double quotes on the field instead of bracket delimiters and
single quotes on the string (or no quotes it it is not a string)
The single quotes around the string have to be escaped with a backslash so
you can wrap the whole query in single quotes.
OR you could wrap it all in tripple quotes and not escape....

...three simultaneous answers. that must get some sort of prize.

Re: I need help on the Update Cursor function

MathewCoyle — Thu, 23 Aug 2012 15:54:35 GMT

...three simultaneous answers. that must get some sort of prize.

The trifecta crown.

Re: I need help on the Update Cursor function

ChrisSnyder — Sat, 11 Dec 2021 18:35:11 GMT

I might add that your original sytax of .setvalue should in fact be .setValue (case now matters in v10.0 +!!!). also, I think your SQL in the cursor statement was incorrect. Note you ONLY need to use the .setValue() method if your field name is a variable.

This should work:

rows = arcpy.UpdateCursor("Parcels", "OBJECTID = 1")
for row in rows:
    row.GENERATED = 'GENERATED'
    rows.updateRow(row)
del row, rows

Alternately, this should also work, and demonstates the proper use of the .setValue() method:

generatedFieldName = "GENERATED"
rows = arcpy.UpdateCursor("Parcels", "OBJECTID = 1")
for row in rows:
    row.setValue(generatedFieldName) = 'GENERATED'
    rows.updateRow(row)
del row, rows

Re: I need help on the Update Cursor function

ChrisSnyder — Sat, 11 Dec 2021 18:35:13 GMT

For SAG's (American slang), here's the v10.1 equivalent using the new "data access" update cursor syntax:

fieldList = ["GENERATED"] #list of the field names you want the cursor to return... order is important
rows = arcpy.da.UpdateCursor("Parcels", fieldList, "OBJECTID = 1")
for row in rows:
    row[0] = 'GENERATED' #fields are now refered to in terms of their index in the fieldList
    rows.updateRow(row)

Re: I need help on the Update Cursor function

OLANIYANOLAKUNLE — Thu, 23 Aug 2012 18:27:02 GMT

Thanks for all your response, but can i start an edit session automatically with arcpy script? Thanks

Re: I need help on the Update Cursor function

MathewCoyle — Thu, 23 Aug 2012 18:42:48 GMT

Thanks for all your response, but can i start an edit session automatically with arcpy script? Thanks

No, that would require ArcObjects.

Re: I need help on the Update Cursor function

OLANIYANOLAKUNLE — Thu, 23 Aug 2012 19:24:52 GMT

This is the new code i constructed:

rows = arcpy.UpdateCursor("Parcels", "FID = 0")
>>> for row in rows:
...     row.setvalue("GENERATED", "GENERATED")
...     rows.updateRow(row)
...

and this is the error message i received:

Runtime error
Traceback (most recent call last):
File "<string>", line 2, in <module>
File "C:\Program Files (x86)\ArcGIS\Desktop10.1\arcpy\arcpy\arcobjects\_base.py", line 28, in __getattr__
    raise AttributeError("%s" % attr)
AttributeError: setvalue

Re: I need help on the Update Cursor function

MathewCoyle — Sat, 11 Dec 2021 18:35:16 GMT

As Chris mentioned earlier, you need to have setValue.

rows = arcpy.UpdateCursor("Parcels", "FID = 1")

for row in rows:
    row.setValue("GENERATED", "GENERATED")
    rows.updateRow(row)

Re: I need help on the Update Cursor function

ChrisSnyder — Thu, 23 Aug 2012 20:10:19 GMT

but can i start an edit session automatically with arcpy script

Actually, in v10.1, yes you can:
http://resources.arcgis.com/en/help/main/10.1/index.html#//018w00000005000000

Although I feel that extra complexity might not be what you actually want to do in this case...

Re: I need help on the Update Cursor function

OLANIYANOLAKUNLE — Thu, 23 Aug 2012 20:16:15 GMT

mzcoyle, please there is no difference between the code you pasted and the code i used? Please can you elaborate on the setvalue? Thanks

Re: I need help on the Update Cursor function

ChrisSnyder — Thu, 23 Aug 2012 20:43:32 GMT

setvalue vs setValue

Python is case sensitive... Meaning there is a difference between upper case (V) and lower case (v).

Re: I need help on the Update Cursor function

OLANIYANOLAKUNLE — Thu, 23 Aug 2012 20:56:06 GMT

I used your code

Code:
rows = arcpy.UpdateCursor("Parcels", "FID = 1")

for row in rows:
row.setValue("GENERATED", "GENERATED")
rows.updateRow(row)

i did not get any error but the record was not updated? Any suggestions

Re: I need help on the Update Cursor function

ChrisSnyder — Sat, 11 Dec 2021 18:35:19 GMT

Only use setValue() if the field name is a variable.

if your field IS NOT a variable:

rows = arcpy.UpdateCursor("Parcels", "FID = 1")
for row in rows:
    row.GENERATED = "GENERATED"
    rows.updateRow(row)

if your field IS a variable:

myField = "GENERATED"
rows = arcpy.UpdateCursor("Parcels", "FID = 1")
for row in rows:
    row.setValue(myField,"GENERATED")
    rows.updateRow(row)

Re: I need help on my pdf output

OLANIYANOLAKUNLE — Thu, 23 Aug 2012 21:02:17 GMT

i want to generate a pdf output by using the arcpy.exporttopdf function, i want the final output to use this nomenclature for naming the pdf output (plot_no.pdf); the plot_no would be derived from an attribute value under the field named plot_no in the attribute table. Please do you have any suggestions. Thanks

Re: I need help on the Update Cursor function

OLANIYANOLAKUNLE — Thu, 23 Aug 2012 21:12:05 GMT

Thanks all i got it with all your suggestions, what happened was that i had to start an edit session to be able to see the changes. With this i have some layers from a parcel fabric within my dataframe which makes it difficult for me to use the edit = arcpy.da.Editor(workspace) it throws this error - can not open workspace. Any suggestion would go a long way. Thanks

Re: I need help on the Update Cursor function

OLANIYANOLAKUNLE — Thu, 23 Aug 2012 22:30:32 GMT

Im trying to automatically get the system time and date updated with the update cursor script, this is my script and the error

myField = "Date_Gener"
>>> rows = arcpy.UpdateCursor("Parcels")
>>> for row in rows:
...    row.setValue(myField,'Date ( )')
...    rows.updateRow(row)
...
Runtime error
Traceback (most recent call last):
File "<string>", line 2, in <module>
File "C:\Program Files (x86)\ArcGIS\Desktop10.1\arcpy\arcpy\arcobjects\arcobjects.py", line 1007, in setValue
    return convertArcObjectToPythonObject(self._arc_object.SetValue(*gp_fixargs(args)))
RuntimeError: ERROR 999999: Error executing function.
The value type is incompatible with the field type. [Date_Gener]

Any suggestions? Please....

Re: I need help on the Update Cursor function

curtvprice — Sat, 11 Dec 2021 18:35:21 GMT

myField = "Date_Gener"
>>> rows = arcpy.UpdateCursor("Parcels")
>>> for row in rows:
...    row.setValue(myField,'Date ( )')
...    rows.updateRow(row)
...

Why not get the date as a string and use the Calculate Field tool? This is easier and much faster than a cursor, even the newfangled arcpy.da flavor.

import datetime
Today = str(datetime.date.today())
arcpy.CalculateField_management("Parcels","date_Gener","'" + Today + "'","PYTHON")

This will only calculate the value for selected rows of the layer "Parcels".