Create a new df column using a function where the inputs are df columns

Question

I have a df with 2 columns (A, B) I also have a function sd = sd.(input 1, input 2).

I would like to create a new df col, where

df["newcolumn"] = sd.(df(A), df(B))

Any help would be great, Thanks.

df[newcolumn] = sd.(df.apply["A"], df.apply["B"])

error = name 'applydf' is not defined.