Debugging reason for python running unreasonably slow when adding numbers

[Chris Angelico]

On Thu, 16 Mar 2023 at 02:14, Thomas Passin <list1 at tompassin.net> wrote:
>
> On 3/15/2023 11:01 AM, Chris Angelico wrote:
> > On Thu, 16 Mar 2023 at 01:26, David Raymond <David.Raymond at tomtom.com> wrote:
> >> I'm not quite sure why the built-in sum functions are slower than the for loop,
> >> or why they're slower with the generator expression than with the list comprehension.
> >
> > For small-to-medium data sizes, genexps are slower than list comps,
> > but use less memory. (At some point, using less memory translates
> > directly into faster runtime.) But even the sum-with-genexp version is
> > notably faster than reduce.
> >
> > Is 'weights' a dictionary? You're iterating over it, then subscripting
> > every time. If it is, try simply taking the sum of weights.values(),
> > as this should be significantly faster.
>
> It's a list.
>

Then I'm very confused as to how things are being done, so I will shut
up. There's not enough information here to give performance advice
without actually being a subject-matter expert already.

ChrisA