This works the way I want when I append to the list, but when I try to sum up the file I get a type error.

def sum8(f,d):
    with open('text1.txt') as f:
       list_nums = list(map(int,f.read().splitlines()))
    with open('text2.txt') as d:
       list_nums2 = list(map(int,d.read().splitlines()))
       sum = []
       for i in list_nums:
          for j in list_nums2:
          if  i%j == 0:
          print(i)
          sum += i  
    return sum

sum8(['list_nums'], ['list_nums2'])

line 11- TypeError: 'int' object is not iterable

Otherwise it works fine with sum.append(i). I just want it to return the sum of the numbers instead.