How to implement sql coalesce in pandas

Question

I have a data frame like

df = pd.DataFrame({\"A\":[1,2,np.nan],\"B\":[np.nan,10,np.nan], \"C\":[5,10,7]})
     A     B   C
0  1.0   NaN   5
1  2.0  10.0  10         


        

Answer 1

I think you need bfill with selecting first column by iloc:

df['D'] = df.bfill(axis=1).iloc[:,0]
print (df)
     A     B   C    D
0  1.0   NaN   5  1.0
1  2.0  10.0  10  2.0
2  NaN   NaN   7  7.0

same as:

df['D'] = df.fillna(method='bfill',axis=1).iloc[:,0]
print (df)
     A     B   C    D
0  1.0   NaN   5  1.0
1  2.0  10.0  10  2.0
2  NaN   NaN   7  7.0