topic Re: How to identify if 0 records are selected in a layer using python in ArcGIS API for Python Questions

How to identify if 0 records are selected in a layer using python

AhnaMiller2 — Tue, 07 Nov 2017 20:06:17 GMT

I am currently working on a script that reads the number of features selected in a layer and returns a message or does a function based on how many records are selected.

If 0 are selected: it tells the user to "make a selection"

If >10, it tells users "too many features selected, must be less than 10"

If they select between 1-10 features, it runs the rest of the function.

I have the following logic:

features = int(arcpy.GetCount_management (featureLayer).getOutput(0))

if features<1:

arcpy.addmessage(msg1)

elif features>10:

arcpy.addmessage(msg2)

else:

function proceeds....

The issue with this logic is that if no features are selected (if features<1:) it reads it as the count of the entire feature class and so returns msg2.

I tried instead to use the logic of

desc = arcpy.Describe (Featureclass)

if desc.FIDset ==' ':

arcpy.addmessage (msg1)

This second logic works in ArcGIS desktop, but will not work in AGOL if I publish as a Geoprocessing service.

Can anyone think of any workarounds that will recognize if 0 records are selected?

Re: How to identify if 0 records are selected in a layer using python

DanPatterson_Retired — Tue, 07 Nov 2017 20:07:52 GMT

GetCount_management is one way

Re: How to identify if 0 records are selected in a layer using python

AhnaMiller2 — Tue, 07 Nov 2017 20:11:27 GMT

Thanks Dan, the issue with GetCount_management is that if I have nothing selected, it sees all the records in the layer so it retruns message 2 (too many features selected) instead of message1 (no features selected)

Re: How to identify if 0 records are selected in a layer using python

JamesMacKay3 — Tue, 07 Nov 2017 20:25:00 GMT

I haven't tried this with AGOL data, but getSelectionSet() on the arcpy.mapping.Layer class might be worth a look.

Re: How to identify if 0 records are selected in a layer using python

DanPatterson_Retired — Sun, 12 Dec 2021 08:59:13 GMT

while True:
    n = input("Enter a number between 1 and 10:  ")
    if int(n) > 0 and int(n) <11:
        print('done')
        break 
    

Enter a number between 1 and 10:  0

Enter a number between 1 and 10:  11

Enter a number between 1 and 10:  2


done
‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

then you could switch the idea up a bit in a while loop perhaps while

But you mentioned agol... hmmm don't do it, but the logic is

Re: How to identify if 0 records are selected in a layer using python

XanderBakker — Sun, 12 Dec 2021 08:59:15 GMT

Hi Ahna Miller , can you clarify where you want to execute the Python code?

When you use:

desc = arcpy.Describe(Featureclass)
if desc.FIDset != '':
    # you have a selection
    print("Number of selected features: {}".format(len(desc.FIDSet.split(";"))))‍‍‍‍

you should not pass in a "FeatureClass" (reference to a featureclass stored on disk) since it will never have a selection. You will have to reference a layer in a ArcMap or ArcGIS Pro session to make this work.

Your comment:

This second logic works in ArcGIS desktop, but will not work in AGOL if I publish as a Geoprocessing service.

... has confused me.

There are two things that needs clarification:

"will not work in AGOL"; are you loading a hosted feature service in Desktop and run the code in desktop?
"if I publish as a Geoprocessing service"; where is the geoprocessing service published? Not is AGOL because as far as I know you can only publish this in server.

Since you posted this question in the ArcGIS Python API space, you might be working with this API in a Jupyter notebook, but then the question arises if you would reference a web map with your layer how will you make the selection? So my question is, what is your specific use case, what would you like to achieve and where and for whom?

Re: How to identify if 0 records are selected in a layer using python

AhnaMiller2 — Thu, 16 Nov 2017 17:40:29 GMT

Hi Xander,

To clarify- I am attempting to use this python code as a geoprocessing tool in AGOL webapp builder. I test from desktop before publishing as a GP service, but ultimately the script needs to work as a GP service from the geoprocessing widget in WAB.

Re: How to identify if 0 records are selected in a layer using python

XanderBakker — Thu, 16 Nov 2017 17:53:10 GMT

So, I still have a question about which selection made where should be detected by the GP service executed in WAB? It should detect the selection made in the WAB by the current user?

Re: How to identify if 0 records are selected in a layer using python

AhnaMiller2 — Mon, 20 Nov 2017 18:24:16 GMT

xander_bakker‌ , yes. It should detect the selection made in the WAB by the current user.

Re: How to identify if 0 records are selected in a layer using python

XanderBakker — Mon, 20 Nov 2017 22:11:16 GMT

I don't think a GP service run at the server is capable of detecting a selection that "lives" at a client. You should probably code this.

Let me tag rscheitlin‌ and rastrauch who will probably have an answer to this.

Re: How to identify if 0 records are selected in a layer using python

RobertScheitlin__GISP — Tue, 21 Nov 2017 02:38:53 GMT

Yes I have to agree with Xander here, I do not think it is possible for a GP process to know of a client side selection in WAB using the GP Widget.

Re: How to identify if 0 records are selected in a layer using python

ChrisHolmes — Fri, 23 Feb 2018 00:02:19 GMT

Hi Ahna, curious if you found a solution?

Thanks

Re: How to identify if 0 records are selected in a layer using python

AhnaMiller2 — Fri, 02 Mar 2018 16:03:47 GMT

Hello Chris, I ended up using a work around that identified a range of features a user could select and run the function for.My database had more than 20000 features, so I set that a selection range had to be between 1 & 200, If a user did not select anything, it would read it as if all 20000 features were selected & so the function would not run. Not the most ideal solution, but a work around nonetheless. I'd be happy to share this part of the code logic with you if it would help.

Re: How to identify if 0 records are selected in a layer using python

MattDriscoll1 — Fri, 27 Apr 2018 15:31:11 GMT

Could you please share the code, I am running into the same problem. Thank you!

Re: How to identify if 0 records are selected in a layer using python

AhnaMiller2 — Sun, 12 Dec 2021 08:59:18 GMT

Hi Matt,

Here's the code I ended up using to get around this- I basically set it so that a user had to select between 1 - ### features to run the script. This way, if a user does not select between 1 and ##(say 25) , the script will attempt to run on the entire data set, which will then throw the error message in Line 12

featureLayer = arcpy.GetParameter(0) #this line respects the selection
listA =[]

##Add selected features to listA as needed

if len(listA) in range (1,26): #this is the line that ensures something gets selected as long as the dataset is more than 25 features
     with arcpy.da.UpdateCursor([insertlayerhere], ([comma separated fields here])) as uc:
          for row in uc:
                    uc.updateRow(row)
     msg1= "OBJECTID(s) {0} will be InsertActionHere".format(listA)
else:
     msg1="Please select between 1 and 25 valid features."

#pass message 1
arcpy.SetParameterAsText(1, msg1)‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

""""
instead of line ‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍6 / passing everything into a list the following code also works:
   features = int(arcpy.GetCount_management(featureLayer).getOutput(0))‍


"""‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Hope this makes sense, let me know if not, I'd be happy to discuss further!