Python Code for Setting Obtained from Tool property

Question

Is is possible to set the Obtained from property for a parameter in Validation using python code?

I have populated a string parameter with a list of tables selected in Table View parameters.  If the user selects a table name in the string parameter I would like to populate a Field data type parameter with the list of fields for the selected table.

def updateParameters(self):
    """Modify the values and properties of parameters before internal
    validation is performed.  This method is called whenever a parmater
    has been changed."""
       
    if self.params[0].altered:
      tblList = [""]    
      desc = arcpy.Describe(self.params[0].value)
      tblList.append(desc.name)
      if self.params[1].value:
        desc = arcpy.Describe(self.params[1].value)
        tblList.append(desc.name)
      if self.params[2].value:
        desc = arcpy.Describe(self.params[2].value)
        tblList.append(desc.name)
      self.params[6].filter.list = tblList
      self.params[8].filter.list = tblList
      self.params[10].filter.list = tblList
    if self.params[1].altered:
      tblList = [""]
      if self.params[0].value:
        desc = arcpy.Describe(self.params[0].value)
        tblList.append(desc.name)
      desc = arcpy.Describe(self.params[1].value)
      tblList.append(desc.name)
      if self.params[2].value:
        desc = arcpy.Describe(self.params[2].value)
        tblList.append(desc.name)
      self.params[6].filter.list = tblList
      self.params[8].filter.list = tblList
      self.params[10].filter.list = tblList
    if self.params[2].altered:
      tblList = [""]
      if self.params[0].value:
        desc = arcpy.Describe(self.params[0].value)
        tblList.append(desc.name)
      if self.params[1].value:
        desc = arcpy.Describe(self.params[1].value)
       tblList.append(desc.name)
      desc = arcpy.Describe(self.params[2].value)
      tblList.append(desc.name)
      self.params[6].filter.list = tblList
      self.params[8].filter.list = tblList
      self.params[10].filter.list = tblList

if self.params[6].altered:
      At this point I would like to populate self.params[7] with a list of fields corresponding to the table selected in 
      self.params[6]

self.params[7] is currently a Field data type

SuzanneRoulston-Doty · Answer

Thank you everyone for your responses.

Luke_Pinner · Answer

Oh I get you. Use the parameterDependencies attribute.    def getParameterInfo(self):
        '''parameter definitions for GUI'''
        params =[]
        params.append(arcpy.Parameter(
            displayName='GPFeatureLayer1',
            name='GPFeatureLayer1',
            datatype='GPFeatureLayer',
            parameterType="Required",
            direction="Input"))
        params.append(arcpy.Parameter(
            displayName='Field1',
            name='Field1',
            datatype='Field',
            parameterType="Required",
            direction="Input"))

#this will automatically update the fields list with fields from param[0]
        params[1].parameterDependencies = [params[0].name]

SuzanneRoulston-Doty · Answer

Hi Luke,

Using a string data type parameter I have been able to populate a filter list with field names (though your code was more succinct than mine so thank you for the sample code).

I was wondering if I was using a field data type parameter if there was way a to set the value for the 'Obtained from' property, for the field data type parameter, using python code or if that property can only be set manually in the tool's properties dialog box.  The tool I am working lets the user select one of three tables in a value list and based on the selection I want to display a list of the fields for the selected table name.