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

option 1
pandas

df.assign(D=df.lookup(df.index, df.isnull().idxmin(1)))

     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

option 2
numpy

v = df.values
j = np.isnan(v).argmin(1)
df.assign(D=v[np.arange(len(v)), j])

     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

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naive time test
over given data

over larger data