On 8 April 2018 at 08:09, Tim Peters <tim.peters@gmail.com> wrote: [Raymond wrote]:
The docs probably need another recipe to show this pattern:
def prepend(value, iterator): "prepend(1, [2, 3, 4]) -> 1 2 3 4" return chain([value], iterator)
+1. Whether `accumulate()` should grow a `start=` argument still seems a distinct (albeit related) issue to me, though.
I didn't have a strong opinion either way until Tim mentioned sum() and then I went and checked the docs for both that and for accumulate. First sentence of the sum() docs: Sums *start* and the items of an *iterable* from left to right and returns the total. First sentence of the accumulate docs: Make an iterator that returns accumulated sums, ... So I now think that having "start" as a parameter to one but not the other, counts as a genuine API discrepancy. Providing start to accumulate would then mean the same thing as providing it to sum(): it would change the basis point for the first addition operation, but it wouldn't change the *number* of cumulative sums produced. By contrast, using the prepend() approach with accumulate() not only changes the starting value, it also changes the number of cumulative sums produced. Cheers, Nick. -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia