How to remove temporary layers so they don't show up in parameter lists

Question

ArcGis 10.2, arcpy. I have several tools in a Python toolbox that have a feature class parameter. The parameter is defined as parameterType = “GPFeatureLayer”. When running several tools in succession the list of choices for the parameter becomes cluttered with temporary layers created from previously run tools. By temporary I mean layers created with arcpy.MakeFeatureLayer_management(). This list will sometimes include multiple occurrences of the same layer name. I would like to remove all layers from wherever they are coming from so only those layers that are in the TOC show up as choices in the tool parameters. I have tried arcpy.Delete_management() but that resulted in deleting the actual features the layer was generated from rather than the layer (OUCH!). I have also tried emptying out the scratch GDB. Thanks in advance for your input.

Answer 1

After re-reading the documentation on Internal Layers http://resources.arcgis.com/en/help/...0000000m000000, specifically:

When you create a layer or table view using geoprocessing tools, the new layer or table view is stored in an internal layer list, which is a different list from the ArcMap table of contents. This means that geoprocessing actually keeps two lists of layers and table views:

• The list of layers in the ArcMap table of contents

• The internal list of layers created by geoprocessing tools

I can see what I was doing wrong. I thought I was deleting the temporary layers by getting a list of layers for the data frame and deleting from that list:

def clearLayers():
    mxd = arcpy.mapping.MapDocument('CURRENT')
    for df in arcpy.mapping.ListDataFrames(mxd):
        for lyr in arcpy.mapping.ListLayers(mxd, "", df):
            arcpy.mapping.RemoveLayer(df, lyr) 
    del mxd

This was not clearing the internal layer list (layers created by other geoprocessing tools) that the python tools use in part to generate parameter lists. Having arcpy.env.addOutputsToMap = False had no effect on the internal layer list either (which it shouldn't).

To delete from the internal list I am using arcpy.Delete_management() on the temporary layer itself as in:

tempLyr = arcpy.MakeFeatureLayer(features, layerName)

...do other stuff

arcpy.Delete_management(tempLyr, 'GPFeatureLayer')

Answer 2

Could you just use the mapping module to list layers in the TOC?

Something like...

mxd = arcpy.mapping.MapDocument("current")
df = arcpy.mapping.ListDataFrames(mxd)[0]
layers = arcpy.mapping.ListLayers(df)[0]

Then use this list to get names, data source, etc, and use it in a filter of your GPFeatureLayer parameter.