Pandas throws a Future Warning when I apply a function to multiple columns of a groupby object. It suggests to use a list as index instead of tuples. How would one go about this?
>>> df = pd.DataFrame([[1,2,3],[4,5,6],[7,8,9]])
>>> df.groupby([0,1])[1,2].apply(sum)
<stdin>:1: FutureWarning: Indexing with multiple keys (implicitly converted to a tuple of keys) will be deprecated, use a list instead.
1 2
0 1
1 2 2 3
4 5 5 6
7 8 8 9
This warning was introduced in pandas 1.0.0, following a discussion on GitHub. So best use what was suggested there:
df.groupby([0, 1])[[1, 2]].apply(sum)
It's also possible to move the slicing operation to the end, but that is not as efficient:
df.groupby([0, 1]).apply(sum).loc[:, 1:]
Thanks @ALollz and @cmosig for helpful comments.
Use double brackets after the groupby method. Single brackets are used to output a Pandas Series and double brackets are used to output a Pandas DataFrame.
df.groupby([0,1])[[1,2]].apply(sum)