Gapfill pandas dataframe 在另一个 dataframe 中使用同一列中的值

Question

   a1 a2  a3    b1
0  0  0  12   NaN
1  0  3  NaN  NaN
2  2  3  1    NaN

In the dataframe df above, I want to gap-fill column a3 and b1 using median of values from the same columns in another dataframe df2 with the same columns but different values.

   a1  a2  a3  b1
0  0  0  2  6 
1  0  3  3  7
2  2  3  4  8

I tried this: df.fillna(df2.median(), inplace=True) , but I am not sure if it does what I want

Answer 1

I think it does what you want.

The median of a3 in df2 is 3, the median of b1 in df2 is 7.

>>> df.fillna(df2.median())
   a1  a2    a3   b1
0   0   0  12.0  7.0
1   0   3   3.0  7.0
2   2   3   1.0  7.0

So it looks like good, no?