Hi @joshua.stockwell ,
As @ELTuser77 mentioned you need to wrap the list results with square brackets. Effectively, wrapping the square brackets around the results is creating an array of rows of values that match up to the columns in your grid variable. The important thing to note here is that order matters. Meaning if the order of your column values need be in the same order that exists in your grid variable columns. @MichaelBoucht posted a very simplified answer to how this is done a while back which I thought was very simple and easy to understand example of how to do this. You can check that out here: https://matillioncommunity.discourse.group/t/grid-variable-updating-in-python-script/1200
I hope this helps.