184 – accumulate with a custom function

You can use a custom binary function with itertools.accumulate, allowing you to go through an iterable and computing successive accumulated values:

from itertools import accumulate
from operator import mul

print(list(accumulate(
    range(1, 6),
    mul,
)))
# [1, 2, 6, 24, 120]

You can also use a lambda function as the function argument to accumulate. In that case, the left argument is the accumulated value and the right argument is the next value from the iterable:

from itertools import accumulate
from operator import mul

print(list(accumulate(
    range(1, 6),
    lambda acc, v: 2 * acc + v
)))
# [1, 4, 11, 26, 57]