How do I do sum_of_digits recursively for large numbers

Question

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?

Answer 1

You need to use //, the integer division, instead of / (float division). Using / loses precision, which leads to the error you encounter.

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

print(sum_of_digits(228475)) # 28

And it can be done with:

print(sum(map(int, str(228475)))) # 28