I updating one of the parameters in my ArcGIS Python toolbox with data from SQL Server, but am getting an illegal list value error. I have removed a lot of the 'special' characters, but am thinking there should be a list of what constitues an 'Illegal list value'. Does anyone know?

ERROR Traceback (most recent call last): File "", line 276, in updateParameters ValueError: FilterObject: illegal list value

  • Welcome to GIS SE! As a new user be sure to take the Tour to learn about our focussed Q&A format. When precisely do you see this error? I suspect that we may need you to post a test Python toolbox (code snippet equivalent for Python Toolbox question) that can be copy/pasted to run and see what you are describing.
    – PolyGeo
    Commented Mar 2, 2018 at 4:19

1 Answer 1


It had nothing to do with special characters, but there was a NULL value in the column which was causing the error. After removing this row in the database, I was able to update the parameter list.

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