There are three parameters: the input features, the distance, and the output features. The script below creates features based on their distance from parks in the city of Portland.
#Arcgis file format for adding scripts code
Putting such logic in the ToolValidator class bloats your code with logic that has nothing to do with tool validation, and in some cases, you may not know which layer file to use until tool execution. But if you need to set symbology to any one of several layer files, you do so in the script tool. In fact, if you only need to reference one layer file, you should do so either in the script tool's properties or in the initializeParameters method. If you're familiar with programming tool validation logic in a ToolValidator class, you can see that the above code snippet could be rewritten for use in the updateParameters method. Setting symbology in a script versus the ToolValidator class
You can also set the symbology property in the script's symbology code.
When the script tool is run, the output is added to the display using the symbology found in the layer file. The symbology property of a script tool parameter allows you to associate a single layer file (. Setting symbology in a script versus the ToolValidator class.