# Developers Planet

Jorge Gandara 2 weeks ago

### How can I add a list of intergers together using a comprehension?

I'm trying to convert a number to a string, then to a list, then converting the list of numbers into integers, then adding these numbers together.

Here's an example:

``````Number = 123456789
SplitList = (list(str(Number)))
IntergerList = list(int(I) for I in SplitList)
A = 0
A = (A + S for S in IntergerList)
``````

Why doesn't this work?

Mureinik 2 weeks ago

Why reinvent the wheel? Just use the built-in `sum` function:

``````sum(integerList)
``````

Håken Lid 2 weeks ago

You can do it by passing a generator expression to the builtin function `sum`.

``````number = 123456789
sum(int(digit) for digit in str(number))
``````

nknous 2 weeks ago

``````numbers = 123456789
splitNumbers = [int(d) for d in str(numbers)]

sumOfSplitNumbers = sum(splitNumbers)
``````

Damian Lattenero 2 weeks ago

Why transform it to a list? This is a math problem, do the maths :), it's another option just only another:

``````Number = 123456789
res = 0
while(Number != 0):
res += Number % 10
Number = int(Number / 10)
``````

res = 45