Python. Find max sum of digits without arrays

The task is. You have an array of numbers, you should find the max sum of the digits. The numbers are natural.

Constraints: you can not use arrays.

The most interesting part of this code is to get single digits from a number.

#The task is. You have an array of numbers, you should find the max sum of the digits. The numbers are natural.
#Constraints: you can not use arrays

n = 5
max_sum = 0

for i in 123,334,555,1222:
  sum = 0
  is_parsed = False
  step = 0
  const_i = i 
  while(is_parsed == False):
    if step == 0:
      dig = i % 10
    else :
      dig = int((const_i // 10 **step) %10)      
    i = i / 10
    if i < 1:
      is_parsed = True    
    step += 1
    sum += dig
  if sum > max_sum:
    max_sum = sum
      
print('Max sum of digits is: ', max_sum)
     

The link for my tutorial tasks is here: https://replit.com/@alexbbell/Module10#module10_7.py