I'm trying to complete "Practice Makes Perfect", but I'm stuck. I've tried everything already and I still can't pass it. What am I doing wrong?

Here's my code:

def digit_sum(n): #function

x = [] #list

for i in int(n): #looping

if i > 0: a # gr8r than 0

append.i(x) # add every number to the 'x' list

return sum(x) # adding everything in the list

HELP!!!!!!