How can I calculate a rolling window sum in pandas across this MultiIndex dataframe?
If anyone else comes looking, this was my solution:

# find last column
last_column = df.shape[1]-1

# grab the previous 11 columns (also works if there aren't that many in the df)
wanted = df.iloc[:, (last_column-11):last_column]

# calculate the rounded moving annual total 
mat_calc = round(wanted.sum(axis=1)/len(wanted.columns), 2)


Probably not the most pandastic solution, but it works well.