How to make sure, when you groupby lists. You dont get the grouped by rows, with empty lists

My issue is the following

I have the following sample data.

When i run the following line of code.

prod.groupby(['UserId'])['OriginLink'].apply(lambda d : list(d)).reset_index()

I get the following result:

How can i guarantee that it doesn return the empty list in the B row. I tried a few if statement, but it didnt work

Wanted result

>Solution :

You can use a dropna if you want to drop anything that is null

prod.dropna(inplace = True)
prod.groupby(['UserId'])['OriginLink'].apply(lambda d : list(d)).reset_index()