A Multiples question

[Avatar19]

I am a bit confused because i believe I am answering this correctly. This is the question:
If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below 1000.
My code is as follows

def mult(X):
    List = []
    k =1
    while X*k <1000:
        List.append(X*k)
        k+=1
    print List
    print sum(List[:])
mult(3)
mult(5)
print 99500+166833

I just put in some print checks to make sure I am not going crazy, this in my understanding accomplishes the question outputting the sum of all multiples of 3 and 5 below 1000 as "266333"
Could someone just tell me if I am making a very stupid mistake in understanding this?

[bvdet]

Avatar19,

The modulo operator is IDEAL for this problem.

This is completely untested and is not a complete solution:

[i for i in range(1000) if not i%3 or not i%5]

[Avatar19]

I got this:

sum([i for i in range(1000) if i % 3 == 0 or i % 5 == 0])

which seems to do it very neatly
Thanks