Examples

In [1]:
import numpy as np
import pandas as pd
In [2]:
x = pd.Series([1, 2, 2, np.nan], index=['p', 'q', 'r', 's'])
x
Out[2]:
p    1.0
q    2.0
r    2.0
s    NaN
dtype: float64

In [3]:
y = pd.Series([2, np.nan, 1, 1], index=['p', 'q', 's', 't'])
y
Out[3]:
p    2.0
q    NaN
s    1.0
t    1.0
dtype: float64

In [4]:
x.add(y, fill_value=0)
Out[4]:
p    3.0
q    2.0
r    2.0
s    1.0
t    1.0
dtype: float64