python - how do I perform the specific operation in dataframe-CodePudding

This is my dataframe

import pandas as pd
df = pd.DataFrame({'3a': [-23, 12, -12, 10, -23, 12, -32, 15, -20, 10],
                   '4b': [-30, 20, -21, 15, -33, np.nan, np.nan, np.nan, np.nan, np.nan],
                   '5c': [-40, 25, -26, 19, -39, np.nan, np.nan, np.nan, np.nan, np.nan],
                   '6d': [-45, 34, -29, 25, -53, np.nan, np.nan, np.nan, np.nan, np.nan],
},index= ['A1','A2','A3','A4','A5','A6','A7','A8','A9','A10'])

How do I replace the np.nans in row A6 and A7 with the values in below dataframe

df1 = pd.DataFrame([[1,2,3],[3,4,5]],index=['A6','A7'],columns=['4b', '5c', '6d'])

CodePudding user response：

you can update update, since the index is matching in the two DF, the null values will get updated with the ones from df1 into df.

use overwrite=false, to only update the NaN values

df.update(df1,overwrite=False)

     3a        4b      5c     6d
A1  -23     -30.0   -40.0   -45.0
A2   12      20.0    25.0    34.0
A3  -12     -21.0   -26.0   -29.0
A4   10      15.0    19.0    25.0
A5  -23     -33.0   -39.0   -53.0
A6   12       1.0     2.0     3.0
A7  -32       3.0     4.0     5.0
A8   15       NaN     NaN     NaN
A9  -20       NaN     NaN     NaN
A10  10       NaN     NaN     NaN