If you want to sum the digit of a number, one way to do it is using `sum()`

+ a generator expression:

sum(int(i) for i in str(155))

I modified a little your code using `sum()`

, maybe you want to take a look at it:

birthday = raw_input("When is your birthday(mm/dd/yyyy)? ") summ = sum(int(i) for i in birthday[0:2]) sumd = sum(int(i) for i in birthday[3:5]) sumy = sum(int(i) for i in birthday[6:10]) sumall = summ + sumd + sumy print "The sum of your numbers is", sumall sumln = sum(int(c) for c in str(sumall))) print "Your lucky number is", sumln