sum() vs. loop

Christian Gollwitzer auriocus at
Sun Oct 10 05:28:54 EDT 2021

Am 10.10.21 um 10:49 schrieb Steve Keller:
> I have found the sum() function to be much slower than to loop over the
> operands myself:
> def sum_products(seq1, seq2):
>      return sum([a * b for a, b in zip(seq1, seq2)])
> def sum_products2(seq1, seq2):
>      sum = 0
>      for a, b in zip(seq1, seq2):
>          sum += a * b
>      return sum
> In a program I generate about 14 million pairs of sequences of ints each
> of length 15 which need to be summed.  The first version with sum() needs
> 44 seconds while the second version runs in 37 seconds.

The first version constructs a list, sums it up and throws the list 
away, while the second version only keeps the running sum in memory. How 
about a generator expression instead, i.e.

             sum((a * b for a, b in zip(seq1, seq2)))

(untested) ?


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