a = pd.Series([4, 5, 6, 7], index=[1, 2, 3, 4])
b = pd.Series([49, 54, 62, 74], index=[2, 6, 4, 0])
a2, b2 = a.align(b, join='inner')
Idiomatic way of only selecting certain rows from a dataframe (whose index exists in other dataframes)