import numpy as np
import pandas as pd
s=pd.Series([12,33,45,23,np.nan,np.nan,66,54,np.nan,99])
df=pd.DataFrame({'value1':[12,33,45,23,np.nan,np.nan,66,54,np.nan,99,100],
'value2':['a','b','c','d','e',np.nan,np.nan,'f','g',np.nan,'g']})
print(s)
s.ffill(0,inplace=True)
print(s)
print(df)
'''
method:pad/ffill:用前面的值填充
backfill/bfill:用后面的值填充
'''
df["value1"].fillna(method='backfill',inplace=True)
print(df)