I'd like the red x to show in the corner of the tool if they try to load the wrong feature class. That way we can prevent possible errors with the output. I've tried using the error messages arcpy functions but I only get the error message function after I select ok for the tool to run.

def getParameterInfo(self):
# First parameter
in_features = arcpy.Parameter(displayName="Data",name="Data",datatype="DEFeatureClass",parameterType="Required",direction="Input")
messages.addMessage("Must Use Data Feature Class!!!!!")
return [param0]

This will set the parameters so that any other feature class that isn't named "Data" can not be used. However, it gives the following error message. I would prefer to be able to customize the red x message saying that you can only input the "Data" feature class. enter image description here


The Set Error Message also gives the invalid drop item warning. I'd rather have it as the red x in the corner and the pop up box.

1 Answer 1


You are referring to the tool parameter validation. This can be achieved with tool validator class either when you use the script tools or pure Python tools (for those you work directly with the parameters in the script).

  • I've looked at the tool validator class and I haven't been able to get it to work. Do you have any examples of it working? Aug 25, 2015 at 15:10

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