The difference between the agg () function and the Apply () function in pandas

If the call to the custom top_n takes the agg function, then the reported error will be

Illustrates a problem, using the AGG function to call Top_n, it is trying to use top_n for each packet aggregation, but the role of Top_n is a sort, not aggregation, so will definitely error

So in this case, you can only use the Apply function, not the AGG function, the function called within the AGG function can only be used to aggregate the grouping.

Beginners, personal understanding, if there are errors, hope understanding

The difference between the agg () function and the Apply () function in pandas