Dear Community

When defining parameters in a .pyt (Python toolbox) I would like to make one of the parameters optional - I think.

It's a boolean parameter, allowing the user to specify weather the tool is allowed to overwrite certain values.

I have made it default to False, and that would be the correct setting in 9 of 10 cases, so I would prefer if the tool would be able to just go with this default value. Unfortunately, when run, the tool insist that I toggle the boolean, before it will remove the little green dot. If I run the tool with the default values untouched, it gives me an error-box saying: "ERROR 000735: Overwrite Existing OBJNAM and NOBJNM: Value is required"

I have tried to change the parameter from parameterType="Required", to parameterType="Optional", but it seems to have no effect on the tool behaviour.

I have decided to paste the entire code here, it's still 90% cut-and-paste from ArcGIS Help (10.2, 10.2.1, and 10.2.2) , ArcGIS Help (10.2, 10.2.1, and 10.2.2) , and others but I guess the error is in a combination of things, and not the isolated line.

I have marked the parameter (line 81), that I try to change to make a difference.

#-------------------------------------------------------------
# Name:       GNDBtoolbox.pyt
# Purpose:    A python-toolbox to work with the "Greenlandic Names Data Base" (GNDB) and NIS.
# Author:     Martin Hvidberg
# e-mail:     mahvi@gst.dk, Martin@Hvidberg.net
# Created:    2014-09-16
# Copyright:  CopyLeft
# ArcGIS ver: 10.2.0
# Python ver: 2.7.3
#-------------------------------------------------------------


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 = "The_GNDB_Toolbox"
        self.alias = "Toolbox to work with GNDB and NIS"
        self.description = "This is the description of the toolbox..."

        # List of tool classes associated with this toolbox
        self.tools = [GNDBruninTOC]
        

class GNDBruninTOC(object):

    """
    GNDB update NIS - assuming feature classes all ready opened in TOC
    Created on 27 Sep 2011
    @author: mahvi@gst.dk / Martin@Hvidberg.net
    
    """
    
    def __init__(self):
        """Define the tool (tool name is the name of the class)."""   
        
        self.label = "GNDB_update_NIS_run_in_TOC"
        self.description = "This tool will update the selected NIS FC, which must be in the TOC"
        self.canRunInBackground = True # True = Obey "Background Processing setting" in the Geoprocessing Options dialog.

    def getParameterInfo(self):
        """Define parameter definitions"""

        # 0. The Feature layer to receive GNDB names
        param0 = arcpy.Parameter(
            displayName="Input Features",
            name="in_features",
            datatype="GPFeatureLayer",
            parameterType="Required",
            direction="Input")
    
        # 1. The point feature class holding the GNDB
        param1 = arcpy.Parameter(
            displayName="GNDB points",
            name="GNDB",
            datatype="GPFeatureLayer",
            parameterType="Required",
            direction="Input")    
        param1.value = "NamesP"
    
        # 2. The Mode
        param2 = arcpy.Parameter(
            displayName="The Mode",
            name="Mode",
            datatype="GPString",
            parameterType="Required",
            direction="Input")            
        param2.filter.type = "ValueList"
        param2.filter.list = ["Berit", "Test"]
        param2.value = param2.filter.list[0]
    
        # 3. Overwrite
        param3 = arcpy.Parameter(
            displayName="Overwrite Existing OBJNAM and NOBJNM",
            name="Overwrite",
            datatype="GPBoolean",
            parameterType="Optional",   # <------ This seems to have no effect ?
            direction="Input")    
        param3.value = "False"          
        
        params = [param0, param1, param2, param3]
    
        return params

    def isLicensed(self):
        """Set whether tool is licensed to execute."""
        return True

    def updateParameters(self, parameters):
        """Modify the values and properties of parameters before internal
        validation is performed.  This method is called whenever a parameter
        has been changed."""
        return

    def updateMessages(self, parameters):
        """Modify the messages created by internal validation for each tool
        parameter.  This method is called after internal validation."""
        return

    def execute(self, parameters, messages):
        """The source code of the tool."""
        # put processing here ...
        return