How do I do sum_of_digits recursively for large numbers

Currently, I have written a recursive function to do sum_of_digits but it works for smaller numbers, e.g. Less than 6.

But for larger numbers, the calculation messes up for some reason.

def sum_of_digits(i):
    if i == 0 :
        return i
    else:
        return i % 10 + sum_of_digits(i / 10)

sum_of_digits(228475) 
# returns 31.111111111111107 
# should be returning 28 instead

What am I doing wrong here?

>Solution :

You should use "integer division (operator //)" instead of normal division (operator /) in the 5th line.

...
        return i % 10 + sum_of_digits(i // 10)
...

Integer division return the largest integer smaller than the result of normal division.
For example,

5/2 = 2.5  =>  5//2 = 2
-5/2 = -2.5  =>  -5//2 = -3