Groupby agg is a bit of an exception. It’s returning something that is very different from the original. Not just a modification, but a different table that sum

Groupby agg is a bit of an exception. It’s returning something that is very different from the original. Not just a modification, but a different table that summarizes the original. You ought to be assigning it to a new variable. Groupby->agg is a good one to chain because you don’t want the intermediary almost ever. Edit: also, I never understand people who use query. That just seems like it’s begging for problems later on. .loc for life.