nav[aria-label="Primary Navigation"] { padding: 0; & ul { list-style: none; width: 100%; display: flex; flex-direction: row; justify-content: start; align-items: start; gap: 30px; padding: 0; & li { margin: 0; } & ul li { list-style: none; } } }

Set default value for a field in ArcMap using python

StacyMcNeil

I have been trying to figure out how I can set a default value to a field in ArcMap. I see there is a tool called Assign Default to field but that is applied to the entire dataset. I would like the default to apply to the current ArcMap session only. In the Create Features window you can right click a layer and set a default there to get the behavior I would like but am trying to accomplish this for multiple layers in the TOC using python.

This is what I have been trying, starting with one layer first, but get an error "The attribute 'defaultValue' is not supported on this instance of Field" I can print the defaultValue however.

feature_class = "Roads"

fields = arcpy.ListFields(feature_class)

for field in fields:

if field.name == "Project_Name":

field.defaultValue = "Test_Project"

Forgive me if I am making an obvious mistake. I am still a beginner. Thanks for any help!

Najděte více příspěvků označených jako

Accepted answers

All comments

AndrewQuee

Hi Stacy, we're looking at a very similar job to your original post. Could you please post your sample code? If it's too long Pastebin.com would be fine.

StacyMcNeil

Hi Nils. Sorry it took me so long to answer you. There is no way to do this with ArcPy. I had to learn some ArcObjects to accomplish this. You can set a default value through the layer extensions (ILayerExtension) and then access the template manager (IEditTemplateManager) and edit the template (IEditTemplate). One problem I ran into that is now logged as a bug is that you have to start an edit session for this to work. If you would like some sample code let me know.

NilsBabel

Hi Stacy, did you ever find a solution to this? I'm trying to do something very similar. Seems like you'd have to access the edit features template to change the default value only in the map document. I haven't found a way to do that in ArcPy.

StacyMcNeil

Thanks Jeff. I will look at that. Thanks to all others who tried to help me! Just to be sure,before I give up, there is no way to access the Create Feature Template Properties with python and I cannot use field.defaultValue to assign a default? Many thanks!

JeffWard

Have you looked at the Attribute Assistant? It allows you to establish a default value for a field.

You need to have a table called DynamicValue added to your map.

The Attribute Assistant has a method called EXPRESSION that would allow you to put a value in a field.

I actually just tested this on a feature class called Roads with a text field of Project_Name. The entry in the DynamicValue table looks like this

I don't think there's a place you can download the Attribute Assistant by itself. It comes packaged with the Local Government map templates in the maps and apps folder that comes with the bundle. You can download the Address Management template here, open up the template and look at their DynamicValue table to see how it is configured.

curtvprice

No, it isn't possible because that default value is a property of the data, not an mxd which points to it.

StacyMcNeil

Thanks Dan. I haven't used functions much. I did get it to run but as I thought, the default value was assigned to the feature class itself so when I go to another map the same default value is present. That is why I was trying to use the defaultValue property for the field. What I really need is a default on a field that will exist for in the mxd only. Just like how you can set it in the template properties when creating a new feature. Maybe this is not possible.

SepheFox

import os

import arcpy

def AssignDefault(tbl, fld):

try:

fname = arcpy.ListFields(tbl, fld)[0].name

mxd = arcpy.mapping.MapDocument("CURRENT")

default = os.path.splitext(arcpy.Describe(mxd.filePath).name)[0]

arcpy.AssignDefaultToField_management(tbl, fname, default)

print default

except:

print("Could not assign default")

AssignDefault("Roads", "Project_Name")

DanPatterson_Retired

you never call the function ie

AssignDefault(tbl, fld)

is needed as a line, and the function itself should be put at the top of your script after the import statements

StacyMcNeil

import os  
import arcpy
tbl = "Roads"
fld = "Project_Name"
def AssignDefault(tbl, fld):  
    try:  
        fname = arcpy.ListFields(tbl, fld)[0].name  
        mxd = arcpy.mapping.MapDocument("CURRENT")  
        default = os.path.splitext(arcpy.Describe(mxd.filePath).name)[0]  
        arcpy.AssignDefaultToField_management(tbl, fname, default)
        print default
    except:  
        print("Could not assign default")

Thanks Curtis. I will be creating a tool for the user to enter their Project Name but am keeping this simple for now since I don't even know what I am trying to do is possible. I ran your code frmo ArcMap but nothing happened. I added a print statement and that was not displayed either. Any ideas?

curtvprice

Here's a function implementation. BTW mxd does not a name property, just filePath.

import os
import arcpy
def AssignDefault(tbl, fld):
    try:
        fname = arcpy.ListFields(tbl, fld)[0].name
        mxd = arcpy.mapping.MapDocument("CURRENT")
        default = os.path.splitext(arcpy.Describe(mxd.filePath).name)[0]
        arcpy.AssignDefaultToField_management(tbl, fname, default) 
    except:
        print("Could not assign default")

SepheFox

for field in fields:

if field.name == "Project_Name":

mxd = arcpy.mapping.MapDocument("CURRENT")

default = mxd.name()

arcpy.AssignDefaultToField_management(feature_class, "Project_Name", default)

curtvprice

I need the default to change from map to map. Any ideas on that?

You could package the mxd with a toolbox, with a model or script tool that runs that default value tool with a parameter for the value you set up or have them pick from a list. You can even a button on a toolbar in the mxd interface - and instruct the user to run it before editing.

Outside of that you would have to build an AddIn which may be more than you want to get into right now. That also would be a different learning curve on the user end (loading the addin, adding it to the interface) so I would prefer the first method anyway.

blake.terhune

There's no easy, built-in way to do this. Have you considered using Subtypes? You can have different default field values based on whatever is chosen for the subtype.

StacyMcNeil

Thanks Christian and Sephe. I have tried th Assign Default to Field tool and the default value then gets applied to the entire feature class so anyone editing will have the same default value. I need the default to change from map to map. Any ideas on that?

Christian_Wells

Hi Stacy,

Try out the Assign Default To Field (Data Management) tool.

feature_class = "Roads"
fields = arcpy.ListFields(feature_class)

for field in fields:
     if field.name == "Project_Name":
          arcpy.AssignDefaultToField_management(feature_class, "Project_Name", "Test_Project")

SepheFox

Hi Stacy, it looks like you're on the right track. Try using Assign Default Values, instead of field.defaultValue: Assign Default Values.

Připojte se k diskusi

Přihlášení členové mohou přispívat, sledovat aktualizace a další. Jste tu noví? Zaregistrujte si bezplatný účet.

Rychlé odkazy

Community Help
Find useful guides, FAQs, and documents to help you navigate and make the most of Esri Community.