I am relatively new to ArcPy 10. and I want to return the list of feature class from a dataset. I can see them through the message, but cannot see them from the result window. Actually there are only inputs, environments and messages I can view from the results window. Am I missing something in the script? Thanks.

    import arcpy
    import json
    from arcpy import env
    featureDatasets = arcpy.ListDatasets("SDE.POINT_OF_INTEREST")
    fcList=arcpy.ListFeatureClasses("*", "ALL", fd)
    for fc in fcList:
    arcpy.AddMessage("--------Encode the list to a json string-\n")
    print layerlistEncode
    arcpy.AddMessage("--------Encode the json string to a list\n")
    print layerlistDecode
    print layerlistDecode["resource"]
    arcpy.SetParameterAsText(0, layerlistEncode)


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  • 1
    Is this a script tool? How have you set up its parameters? If I'm interpreting your code correctly, parameter 0 should probably be a derived, output parameter. Is that how it is set up?
    – blah238
    Oct 3, 2012 at 20:36
  • Yes. It is a script tool. I just want to return the feature layer list as a JSON String for further processing in another tool. I dont set any parameter. I run this script after I add it to a toolbox, but the output is null. I also run it in the python window in ArcGIS, the outputCount is 0.
    – Alex
    Oct 3, 2012 at 21:07
  • 3
    You need to set up a derived, output parameter for SetParameterAsText to have any effect. See the help: help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//…
    – blah238
    Oct 3, 2012 at 21:12
  • 1
    Rather than running the script in the ArcMap python window, I would recommend downloading PythonWin (sourceforge.net/projects/pywin32/files) to write and implement your python/arcpy scripts. This user-friendly interface will definitely help you debug your script too. Beware, that you have to download the correct build for your version of python (2.6 or 2.7).
    – Aaron
    Oct 4, 2012 at 3:29
  • It works. That is what I didnt pay attention to when read the help file. Thanks a lot.
    – Alex
    Oct 4, 2012 at 13:18

1 Answer 1


You need to set up a derived, output parameter for SetParameterAsText to have any effect. See the help on Setting script tool parameters.


  • Thanks blah238. I tried what you told me and it worked. It saved me a lot of time.
    – Alex
    Oct 8, 2012 at 13:31

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