Control the default values for a multivalue input parameter within a Python script-based tool

Summary

Instructions provided on how to use the ToolValidator class to populate default values into the tool dialog for a script-based tool.

Procedure

1. To add custom behavior for your script tool, right-click the script tool, click Properties, then click the Validation tab. On the Validation panel, you can provide Python code that implements a Python class named ToolValidator.
   
   
   
2. In the Python editor, edit the initializeParameters method code block to create a filter list of acceptable values for the corresponding parameter:
   
   
   
3. To make some or all of the filter list values selected by default, pass in a string, separated by semicolons into the parameter:
   
   
   
4. The result of the edited ToolValidator class is a parameter that is updated and set upon opening of the script tool dialog: