PYTHON

what does the combinations itertools in python do

combinations(iterable, r) : It return r-length tuples in sorted order with no repeated elements. For Example, combinations('ABCD', 2) ==> [AB, AC, AD, BC, BD, CD].

combination in python without itertools

#One method that I know works, is the following:

def accumulate(iterable, func=operator.add, *, initial=None):
    'Return running totals'
    # accumulate([1,2,3,4,5]) --> 1 3 6 10 15
    # accumulate([1,2,3,4,5], initial=100) --> 100 101 103 106 110 115
    # accumulate([1,2,3,4,5], operator.mul) --> 1 2 6 24 120
    it = iter(iterable)
    total = initial
    if initial is None:
        try:
            total = next(it)
        except StopIteration:
            return
    yield total
    for element in it:
        total = func(total, element)
        yield total