Adding two pandas dataframes
How about x.add(y, fill_value=0)
?
import pandas as pd
df1 = pd.DataFrame([(1,2),(3,4),(5,6)], columns=['a','b'])
Out:
a b
0 1 2
1 3 4
2 5 6
df2 = pd.DataFrame([(100,200),(300,400),(500,600)], columns=['a','b'])
Out:
a b
0 100 200
1 300 400
2 500 600
df_add = df1.add(df2, fill_value=0)
Out:
a b
0 101 202
1 303 404
2 505 606
If I understand you correctly, you want something like:
(x.reindex_like(y).fillna(0) + y.fillna(0).fillna(0))
This will give the sum of the two dataframes. If a value is in one dataframe and not the other, the result at that position will be that existing value (look at B0 in X and B0 in Y and look at final output). If a value is missing in both dataframes, the result at that position will be zero (look at B1 in X and B1 in Y and look at final output).
>>> x
A B C
0 1 2 NaN
1 3 NaN 4
>>> y
A B C
0 8 NaN 88
1 2 NaN 5
2 10 11 12
>>> (x.reindex_like(y).fillna(0) + y.fillna(0).fillna(0))
A B C
0 9 2 88
1 5 0 9
2 10 11 12