Python toolbox: Setting default values in Value Table

ChrisRingo

Hello all,

I was wondering if anyone can point me in the right direction here.  I'm running ArcGIS Pro 2.9.5 and am creating a tool for a Python Toolbox that will take a bunch of raster layers, and run some statistics on each, among other things. 

So it will take the input rasters and statistic types (SUM, MEAN, etc.) as a Value Table (i.e., datatype='GPValueTable'). My question is how to set a default for a column in this scenario, specifically the Statistic type. In the code snippet below, setting inRasterList.values = [['', '', 'NONE']] sets the default statistic type to NONE for the first raster, but when subsequent rasters are added, the default is not set (which is obvious from the statement syntax).

# -*- coding: utf-8 -*-

import arcpy
class Toolbox(object):
    def __init__(self):
        """Define the toolbox (the name of the toolbox is the name of the
        .pyt file)."""
        self.label = "ForSys Tools (Test)"
        self.alias = "ForSys Tools"

        # List of tool classes associated with this toolbox
        self.tools = [Tool]
class Tool(object):
    def __init__(self):
        """Define the tool (tool name is the name of the class)."""
        self.label = "Sample Rasters"
        self.description = "Sample rasters at point locations"
        self.canRunInBackground = False
    def getParameterInfo(self):
        """Define parameter definitions"""
        inRasterList = arcpy.Parameter(
            displayName="Raster List (Stands are created from first raster)",
            name="strRasters",
            datatype="GPValueTable",
            parameterType="Optional",
            direction="Input"
        inRasterList.parameterDependencies = [inRasterList.name]
        inRasterList.columns = [["GPRasterLayer", "Raster Layer"], ["GPString", "Output Field Name"], ["GPString", "Statistic Type"]]
        inRasterList.filters[2].type = "ValueList"
        inRasterList.filters[2].list = ['NONE', 'MIN', 'MAX', 'MEAN', 'SUM']
        inRasterList.values = [['', '', 'NONE']]
     
        parameters = [inRasterList]
        
        return parameters

So is there some code that can be added to the updateParameters function that will accomplish this? Thanks for any help!

ChrisRingo

Thank you for your replies.  It does seem that Value Tables have some rather annoying behaviors, at least in 2.x. Among these annoyances is the inability to apply defaults past the first row, and equally defeating is that Arc throws an error if not all columns are entered - once you add a row, all columns are required. So you can't apply a default and you can't leave it blank.

Really, all I wanted was the ability to leave the statistics field blank, but Arc throws the error and you can't execute the tool in that case.

So the workaround I'm settling on is this: I found that if you add code to the validation script (specifically updateMessages) to throw a warning when the first raster is entered in the value table, the warning message prevents Arc from throwing the error and preventing the script from executing.  I just made the Warning message informational, as shown in the attached pic.  Pretty kludgy, but the best I could come up with, short of diving into the Pro SDK.  

I'll go ahead and mark it solved.

Warning Message.png