合并具有相同索引的数据帧列表

Question

I would merge a list of dataframes into one, by filling NaN values columns in the same row. The dataframes have the same index as well.

df

        A       B
0       Red     Blue
1       Green   Red

df1

        A       B    Value1  Value2
0       Red     Blue    1.0   NaN
1       Green   Red     NaN   0.2

df2

       A        B     Value1    Value2
1      Green    Red    3.0      NaN
0      Red      Blue   NaN      0.15

Code

df_list = [df1, df2]

df_final = pd.merge(df, df_list, left_index=True, right_index=True)

But got this error TypeError: Can only merge Series or DataFrame objects, a <class 'list'> was passed

Expected Output

        A      B    Value1  Value2
0       Red    Blue   1     0.15
1       Green  Red    3     0.20

Answer 1

You can repeatedly call combine_first with functools.reduce :

from functools import reduce

df_final = reduce(pd.DataFrame.combine_first, df_list, df)

which starts with df as the initial value and then accumulatively invokes combine_first with frames from df_list to give a final frame.

>>> df_final

       A     B  Value1  Value2
0    Red  Blue     1.0    0.15
1  Green   Red     3.0    0.20