Arcpy.mapping.AddLayer selection Funk (serious ESRI devs only)

[JosephArmbruster]

Hey everyone,

It's been ages since i've had to resort to the forums, but the time has come...  This is issue is occurring with:

10.3.0.4322

AND

10.5.1.7333

Problem: When a layer is added to the TOC, just as you see in the snippet below, feature selections will no longer be respected (or at least detected) by geoprocessing tools.

Description: The symptom of the problem is that obtaining the feature selection count of a geoprocessing layer in a python toolbox is inconsistent.  I've pinned it down to some issue with the way Arc (or ArcPy) is handling layers by Name.  Here are some snippets:

# make this an absolute path to some feature class in a geodatabase, you only need a minimum of two features to reproduce the issue, i'm using polygons.

path = #path to your polygon feature class with at least two features in it.

mxd = arcpy.mapping.MapDocument('CURRENT')
new_layer_name = os.path.basename(path)
arcpy.MakeFeatureLayer_management(path, new_layer_name)
new_layer = arcpy.mapping.Layer(new_layer_name)
arcpy.mapping.AddLayer(mxd.activeDataFrame, new_layer_name, 'BOTTOM')

del new_layer
del mxd

Use the code above in a geoprocessing tool to add a layer to the map.

Now, use the code below in a separate geoprocessing tool, to report the number of features selected in the map.

desc = arcpy.Describe(input_feature_class)
if desc.FIDSet:
 messages.addMessage('selection made')
 # you'll never get here with the layer above!!
else:
 messages.addMessage('no selection made')
 # you'll always get here even with a selection 😞

# count will always be the entire feature class count, since no selection was registered
# to the layer....
feature_count = int(arcpy.GetCount_management(input_feature_class).getOutput(0)

Notes:
- If you use the code above to add the feature class to the map.  Remove it from the toc (right click, remove) and add it using arc catalog (drag-drop), the feature selection will STILL not work.  Hence why I suggest it has something to do with the internal name resolution.

- If you start a new ArcMap instance, add the layer by drag-dropping it from Arc Catalog, the selection WILL work.  If you remove this layer and add it using the code above, all subsequent selections will NOT be respected.

I look forward to hearing from ESRI support.

Let me know if you have any questions,

Joseph Armbruster

0Lat Inc, Orlando Florida.

joseph.armbruster@0lat.com

[XanderBakker]

I think Joshua Bixby  has an interesting thing there. I made some small adjustments to the python toolbox and it seems to be working now. 

# Joseph Armbruster - 0Lat Inc - www.0lat.com
# Replace FULL_PATH_TO_A_FEATURE_CLASS_IN_A_GEODATABASE with a full path to a feature class
# Load pyt into arcmap 10.3.X or 10.5.X
# Run AddFeaturesToMap
# Select one feature from the target feature layer using the select tool
# Run GetCount
# Observe the returned feature count...

import arcpy, os

class Toolbox(object):

    def __init__(self):
        self.label = "TEST FOR ESRI"
        self.alias = ""
        self.tools = [
            AddFeaturesToMap,
            GetCount
        ]

class AddFeaturesToMap(object):

    def __init__(self):
        self.label = "For ESRI Add to Map"
        self.description = ""
        self.canRunInBackground = True

    def getParameterInfo(self):
        return

    def isLicensed(self):
        return True

    def updateParameters(self, parameters):
        return

    def updateMessages(self, parameters):
        return

    def execute(self, parameters, messages):

        arcpy.env.overwriteOutput = True

        # dataset_to_process = r'FULL_PATH_TO_A_FEATURE_CLASS_IN_A_GEODATABASE'
        dataset_to_process = r'C:\GeoNet\Selection\test.gdb\myLines'

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

        tmp_new_layer_name = "tmp layer name"
        arcpy.MakeFeatureLayer_management(dataset_to_process, tmp_new_layer_name)
        new_layer = arcpy.mapping.Layer(tmp_new_layer_name)
        new_layer.visible = True
        new_layer.name = os.path.basename(dataset_to_process)
        arcpy.mapping.AddLayer(mxd.activeDataFrame, new_layer, 'BOTTOM')
        arcpy.Delete_management(tmp_new_layer_name)

        del new_layer
        del mxd
        arcpy.RefreshTOC()

        return

class GetCount(object):

    def __init__(self):
        self.label = "For ESRI Get Count"
        self.description = ""
        self.canRunInBackground = True

    def getParameterInfo(self):

        return [
            arcpy.Parameter(
                displayName="Input Geotiles or Grids",
                name="input_geotiles_or_grids",
                datatype="GPFeatureLayer",
                parameterType="required",
                direction="Input")
        ]

    def isLicensed(self):
        return True

    def updateParameters(self, parameters):
        return

    def updateMessages(self, parameters):
        return

    def execute(self, parameters, messages):

        input_feature_class = parameters[0].valueAsText

        desc = arcpy.Describe(input_feature_class)
        fid_set = desc.FIDSet
        if fid_set == '':
            lst_fid = []
        else:
            lst_fid = fid_set.split(';')
        if len(lst_fid) > 0:
            # messages.addMessage('selection made')
            messages.addMessage('selection made: {}'.format(len(lst_fid)))
            messages.addMessage(lst_fid)
        else:
            # messages.addMessage('no selection made')
            messages.addMessage('no selection made: {}'.format(len(lst_fid)))
            messages.addMessage(lst_fid)

        feature_class_name = os.path.basename(input_feature_class)

        feature_count = int(arcpy.GetCount_management(input_feature_class).getOutput(0))
        messages.addMessage('number of features selected: %d' % (feature_count))

        return
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[JoshuaBixby · Accepted solution]

Although not documented, you can point Layer directly to a data set.  Try the following for the execute block:

    def execute(self, parameters, messages):

        dataset_to_process = # path to feature class

        mxd = arcpy.mapping.MapDocument('CURRENT')
        lyr = arcpy.mapping.Layer(dataset_to_process)
        arcpy.mapping.AddLayer(mxd.activeDataFrame, lyr, 'BOTTOM')
        del lyr
        del mxd
        arcpy.RefreshTOC()

        return‍‍‍‍‍‍‍‍‍‍‍‍

[JosephArmbruster]

That's how I had it in my original script.

[XanderBakker]

I just put the code provided by Joshua Bixby  in the Python toolbox and it simply works. No double layers, selection returns the correct values. 

[JoshuaBixby]

So it doesn't work for you?  I am running 10.6 and it works with the tests I have run.

[XanderBakker]

My hands are itching to mark the Joshua's answer as the correct one, since it worked for me too (although we are both using 10.6).

[DanPatterson_Retired]

go for it xander_bakker‌

[XanderBakker]

Let's just wait a moment to see if the OP can confirm the provided solution is working for him... 

[JosephArmbruster]

Correction to my previous comment, this is Not how I had it Exactly... He removed the MakeFeatureLayer management call, which was important !

[JohnDye2]

this was a really funny read