Hi My code is here:

def digit_sum(n):

string = list(str(n))

sum = 0

for n in string:

num = int(n)

sum = sum + num

print sum

numbers = raw_input("Please input you number: ")

digit_sum(numbers)

The error message is this :Oops, try again. Your function fails on digit_sum(434). It returns None when it should return 11.

but in fact ,it't can return the right number.