Confusing Terminology on the Pandas chapter ##Index alignment in DataFrame

[2313499]

I was having a very hard time figuring out

fill = A.stack().mean()
A.add(B, fill_value=fill)

fill = 4.5. However I computed a value of 3.2 because I was taking the mean from the column of A not the DataFrame A. This coming after the Indexing chapter where "explicit is better than implicit." I was thinking that this should be a little more explicit.

[nikhilrsharma]

I did not find this confusing at all