>>> fruits = ['peaches', 'oranges', 'cherries', 'pears']
>>> fruits2 = ['raspberries', 'oranges', 'cherries', 'pears']
>>>
>>> S = pd.Series([20, 33, 52, 10], index=fruits)
>>> S2 = pd.Series([17, 13, 31, 32], index=fruits2)
>>> print(S + S2)
cherries 83.0
oranges 46.0
peaches NaN
pears 42.0
raspberries NaN
dtype: float64
>>>