Debugging reason for python running unreasonably slow when adding numbers

[Thomas Passin]

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.