如何对series进行算术运算操作？

# 如何对series之间进行算法运算
import pandas as pd
series1 = pd.Series([3,4,4,4],['index1','index2','index3','index4'])
series2 = pd.Series([2,2,2,2],['index1','index2','index33','index44'])
# 加法
series_add = series1 + series2
print(series_add)
# 减法
series_minus = series1 - series2
# series_minus
# 乘法
series_multi = series1 * series2
# series_multi
# 除法
series_div = series1/series2
series_div
series是基于索引进行算数运算操作的，pandas会根据索引对数据进行运算，若series之间有不同的索引，对应的值就为Nan。结果如下：
#加法：
index1     5.0
index2     6.0
index3     NaN
index33    NaN
index4     NaN
index44    NaN
dtype: float64
#除法：
index1     1.5
index2     2.0
index3     NaN
index33    NaN
index4     NaN
index44    NaN
dtype: float64