topic Re: how to update field with name of FC for list of FCs ? in Python Questions

how to update field with name of FC for list of FCs ?

GabrielBacca-Cortes — Tue, 10 Feb 2015 22:49:00 GMT

Hi Everybody -

I am trying to fill in the attribute in a newly created field 'Particle', with the name of the FC, which will be changing for a list of FCs. I've tried using 'CalculateField', with which I get the error: 'NameError: name 'xy_1' is not defined', where 'xy_1' is the name of the FC going through the loop.

I've tried using 'UpdateCursor' and I get the error: " 'list' object has no attribute 'setValue' ".

This is the code I've written so far:

fieldName1 = "Particle"

fieldType1 = "TEXT"

fieldlength = 20

wildcard = ""

fctype = ""

try:

fcList = arcpy.ListFeatureClasses(wildcard, fctype)

# print fcList2

for fc in fcList:

print fc

arcpy.AddField_management(fc,fieldName1,fieldType1,"","",fieldlength,"","NULLABLE")

[with:]

desc = arcpy.Describe(fc)

val = desc.name

print val

arcpy.CalculateField_management(fc, fieldName1, val, "PYTHON_9.3")

[OR:]

## curs = arcpy.da.UpdateCursor(fc,fieldName1)

## for row in curs:

## desc = arcpy.Describe(fc)

## val = desc.name

## print val

## row.setValue(fieldName1,val)

## curs.updateRow(row)

## del curs, row

Re: how to update field with name of FC for list of FCs ?

JoshuaBixby — Tue, 10 Feb 2015 23:00:49 GMT

Review the documentation on ArcPy Data Access cursors. The arcpy.da update cursor doesn't have a setValue method, that was for the older-style update cursor. You are effectively mixing up the syntax for the two types of cursors.

Re: how to update field with name of FC for list of FCs ?

JoshuaBixby — Tue, 10 Feb 2015 23:09:59 GMT

With CalculateField_management, try removing "PYTHON_9.3". You aren't actually passing an expression, just a value.

Re: how to update field with name of FC for list of FCs ?

TomSellsted — Tue, 10 Feb 2015 23:11:06 GMT

Gabriel,

It look like you may be confusing how you are using cursors in python. The Data Access module cursors have some distinct differences. You don't need to specify the field for your cursor. This might work:

curs = arcpy.UpdateCursor(fc)

for row in curs:

desc = arcpy.Describe(fc)

val = desc.name

print val

row.setValue(fieldName1,val)

curs.updateRow(row)

del curs, row

Notice that I have removed the .da. from your cursor reference and indented the updateRow line.

Regards,

Tom

Re: how to update field with name of FC for list of FCs ?

XanderBakker — Sat, 11 Dec 2021 23:56:32 GMT

You could do something like this (if you have ArcGIS 10.1 SP1 or higher):

import arcpy, os

# settings for field
fld_name = "Particle"
fld_type = "TEXT"
fld_length = 20

# set you workspace (where the fc's are located)
ws = r"C:\Path\To\Your\Folder\or\fgdb.gdb"
arcpy.env.workspace = ws

fcs =  arcpy.ListFeatureClasses()
for fc_name in fcs:
    fc = os.path.join(ws, fc_name)
    # add field, if it doesn't exist
    if len(arcpy.ListFields(fc, wilc_card=fld_name)) == 0:
        arcpy.AddField_management(fc, fld_name, fld_type, field_length=fld_length)

    with arcpy.da.UpdateCursor(fc, (fld_name)) as curs:
        for row in curs:
            row[0] = fc_name
            curs.updateRow(row)
    del curs, row

Re: how to update field with name of FC for list of FCs ?

GabrielBacca-Cortes — Wed, 11 Feb 2015 14:46:10 GMT

Thanks Joshua - Yes, you're right I was mixing up 'da' cursors with the older version.

Re: how to update field with name of FC for list of FCs ?

GabrielBacca-Cortes — Wed, 11 Feb 2015 14:47:47 GMT

Hi Tom - thanks for the response. Yes, I was mixing 'DA' cursors with the older version.

the changes worked.

regards,

Gabriel

Re: how to update field with name of FC for list of FCs ?

GabrielBacca-Cortes — Wed, 11 Feb 2015 14:52:55 GMT

thanks Xander - this works too, for a more general case. Thanks again..

Re: how to update field with name of FC for list of FCs ?

GabrielBacca-Cortes — Wed, 11 Feb 2015 15:40:51 GMT

Xander - this general version works great when one has to re-run the script through the same set of FCs without redoing previous work. I am sure you knew this but I just figured it out, 🙂 Thanks a bunch !

Re: how to update field with name of FC for list of FCs ?

XanderBakker — Wed, 11 Feb 2015 15:46:44 GMT

You're welcome...

Re: how to update field with name of FC for list of FCs ?

TomSellsted — Wed, 11 Feb 2015 15:52:50 GMT

You are welcome Gabriel!

Re: how to update field with name of FC for list of FCs ?

BlakeTerhune — Wed, 11 Feb 2015 22:42:11 GMT

In the line where you open the update cursor, why do you have extra parenthesis around fld_name?

with arcpy.da.UpdateCursor(fc, (fld_name)) as curs:

Re: how to update field with name of FC for list of FCs ?

TomSellsted — Wed, 11 Feb 2015 22:47:57 GMT

Blake,

It must be a tuple. The extra parenthesis make it a tuple.

Regards,

Tom

Re: how to update field with name of FC for list of FCs ?

GabrielBacca-Cortes — Wed, 11 Feb 2015 22:54:16 GMT

Blake - yes, it is meant for a list of fields, which in my case is only one. As it is use in this link ArcGIS Help 10.1 , scroll down to the updateRow function.

Gabriel

Re: how to update field with name of FC for list of FCs ?

BlakeTerhune — Wed, 11 Feb 2015 23:04:14 GMT

But the Esri documentation for the Update cursor says:

For a single field, you can use a string instead of a list of strings.

I'm not trying to be a nit-pick know-it-all, I'm just trying to understand.

Re: how to update field with name of FC for list of FCs ?

TomSellsted — Wed, 11 Feb 2015 23:07:39 GMT

Blake,

You are correct, the docs do say you can use a string for a single field. In this case just a coding preference. If you had more fields, the tuple would already be in place.

Regards,

Tom

Re: how to update field with name of FC for list of FCs ?

BlakeTerhune — Sat, 11 Dec 2021 23:56:34 GMT

Ah, yes, I follow now. However, I think you have to put an extra comma after the variable inside the parenthesis to make it a true tuple.

fld_name = "Particle"
print fld_name
print (fld_name)
print (fld_name,)

produces:

Particle
Particle
('Particle',)