I want to find a neat way to achieve the following:
Pretend I have a list:
> x = [1, 2, 3, 4, 5]
And a simple function that just adds two numbers:
> def add(a, b)
return a+b
I can reduce the list x directly with:
> sum = reduce(add, x)
> print(sum)
15
Which gives me the sum just fine. But I would like to know the value after each application of add. So using a function similar to reduce, I'd like to get back the following array:
> result = SOME_FUNCTION(add, x)
> print(result)
[3, 6, 10, 15]
Does anybody have a cool way of achieving that. I have a strong preference for using some form of itertools solution if possible :)
Since you want itertools
from itertools import accumulate
list(accumulate(x))
Out [130]:
[1, 3, 6, 10, 15]
Alternatively a generator loop
def cumsum(x):
total = 0
for x in it:
total += x
yield total
list(cumsum(x))
Out [129]:
[1, 3, 6, 10, 15]
Or simply as David mentioned:
np.cumsum(x)
Out [123]:
array([ 1, 3, 6, 10, 15], dtype=int32)