Merge sum rows with multiindex with Pandas

Question

Is it possible to merge and sum rows that appear in both dataframes with multiindex, while adding the ones that are unique to each dataframe.

df1

       Amount1 Amount2 Amount3
A R10  1        1          20
  R3   0        0          20
  X2   1        0          20
B XS1  1        5          10 
  LM2  1        1          10
C RR1  2        1          30

df2

       Amount1 Amount2 Amount3
A R10  1        1          20
  X2   1        0          20
B XS1  1        5          10 
  XF2  1        1          10
C RR1  2        1          30

Final result:

       Amount1 Amount2 Amount3
A R10  2        2          40
  R3   0        0          20
  X2   2        0          40
B XS1  2        10         20 
  LM2  1        1          10
  XF2  1        1          10
C RR1  4        2          60

Answer 1

Try:

df1.add(df2, fill_value=0)

Output:

       Amount1  Amount2  Amount3
A R10      2.0      2.0     40.0
  R3       0.0      0.0     20.0
  X2       2.0      0.0     40.0
B LM2      1.0      1.0     10.0
  XF2      1.0      1.0     10.0
  XS1      2.0     10.0     20.0
C RR1      4.0      2.0     60.0