On Tue, Oct 12, 2021 at 8:55 AM Steve Keller <keller.st...@gmx.de> wrote: > > 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. > > Can someone explain this difference? >
When you use sum, you're constructing a list. Try removing the square brackets: return sum(a * b for a, b in zip(seq1, seq2)) It's also possible that the genexp has more overhead than simply iterating directly, but at very least, this will reduce the memory consumption. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
