Create Excel-like SUMIFS in Pandas

Question

I recently learned about pandas and was happy to see its analytics functionality. I am trying to convert Excel array functions into the Pandas equivalent to au

Answer 1

You want to use the apply function and a lambda:

>> df
     A    B    C    D     E
0  mitfx  0  200  300  0.25
1     gs  1  150  320  0.35
2    duk  1    5    2  0.45
3    bmo  1  145   65  0.65

Let's say I want to sum column C times E but only if column B == 1 and D is greater than 5:

df['matches'] = df.apply(lambda x: x['C'] * x['E'] if x['B'] == 1 and x['D'] > 5 else 0, axis=1)
df.matches.sum()

It might be cleaner to split this into two steps:

df_subset = df[(df.B == 1) & (df.D > 5)]
df_subset.apply(lambda x: x.C * x.E, axis=1).sum()

or to use simply multiplication for speed:

df_subset = df[(df.B == 1) & (df.D > 5)]
print sum(df_subset.C * df_subset.E)

You are absolutely right to want to do this problem without loops.