I have a tool with a ValueTable consisting of two columns - text (GPString) and layer (GPFeatureLayer). When I fill the parameter with desired values (field names in the first column, some feature layers in the second column, I can run the tool.

Problem is that not every row is filled with a layer, so some rows have the field names only. The second row of the value table then returns:

  1. a geoprocessing Layer object if it has been filled with a feature layer or
  2. a geoprocessing value object if it has not been filled with a feature layer.

It looks like this:


I have a problem accessing the values row by row - I want to process all the rows with filled feature layer:

def getParameterInfo(self):
    """Define parameter definitions"""
    param0 = parameter("lokality", "Lokality", "GPFeatureLayer")
    param1 = parameter("value_table", "Atributy a FeatureLayery", "GPValueTable", "Optional")

    param1.columns = [["String", "Atribut"], ["GPFeatureLayer", "Limity"]]

 def execute(self, parameters, messages):
    """The source code of the tool."""
    lokality = parameters[0].valueAsText
    valuetable = parameters[1].value

    for v in valuetable:
       # if v[1] has been filled, it is a geoprocessing layer object. I can check e.g. its name and continue
       if v[1].name:   
          do something

       # if v[1] has not been filled, it is an empty(?) geoprocessing value object, I don´t know how to handle this empty row

How can I check if a layer has been filled and process rows with filled layers only?

  • Try something like if v[1] is None: or if v[1] == None: Does that work?
    – Hornbydd
    Commented Dec 3, 2020 at 13:26
  • Edit: not a LayerObject and ValueObject but "geoprocessing Layer object" and "geoprocessing value object". Interesting that Layer object is with a capital L and value object is not. Question updated.
    – jonlew
    Commented Dec 3, 2020 at 13:32
  • if not v[1]:, if v[1] is None: nor if v[1] == None not working... the empty GPFeatureLayer returns "something" even if it hasn´t been filled with a feature layer... that´s the problem
    – jonlew
    Commented Dec 3, 2020 at 13:39
  • I could possibly put the if v[1].name: to try-except block, so if v[1] was a layer object, it should go on, otherwise it would cast an exception. But I wouldn´t be much happy with this.
    – jonlew
    Commented Dec 3, 2020 at 13:45

1 Answer 1


I was not able to test if the returned object was a geoprocessing Layer object or a geoprocessing value object so I put if v[1].name into try-except block and it works.

for v in valuetable:
      if v[1].name:             
         ...do something with the layer

      ...do something else or don´t do anything (pass)

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