April 10, 2018
12:32 a.m.
Peter O'Connor wrote:
The behaviour where the first element of the return is the same as the first element of the input can be weird and confusing. E.g. compare:
list(itertools.accumulate([2, 3, 4], lambda accum, val: accum-val)) [2, -1, -5] list(itertools.accumulate([2, 3, 4], lambda accum, val: val-accum)) [2, 1, 3]
This is another symptom of the fact that the first item in the list is taken to be the initial value. There's no way to interpret these results in terms of an assumed initial value, because neither of those functions has a left identity. -- Greg