插值

import pandas as pd
import numpy as np

df = pd.DataFrame({'A':[1,2,np.nan,3,np.nan],
                   'B':[1.2,7,3,0,8]})

df['C'] = df.A.interpolate()
df['D'] = df.A.interpolate(method='spline', order=1)

print (df)
     A    B    C         D
0  1.0  1.2  1.0  1.000000
1  2.0  7.0  2.0  2.000000
2  NaN  3.0  2.5  2.428571
3  3.0  0.0  3.0  3.000000
4  NaN  8.0  3.0  3.714286